Friday, November 23, 2012

Earthquakes and Climate Change - Related?


Here is another example of a bright student trying to put things together. Sometimes there are things that are big and in the same place - but are still unrelated:

Q:
I am training to become a teacher, and my professor wants us to become more familiar with supplemental resources, such as this website. So he has asked us to generate a question and submit it to you and then give him the answer we get back. I thank you in advance for your feedback! Question: Are earthquakes, like storms are said to be, tied to climate change? Can you explain why or why not? Thank you so much! 
-Sarah S

A: 
No, earthquakes are not tied to climate change, and the main reason is because of they are not coupled (or very poorly coupled): Other than very temporary shaking of the ground, which is connected very poorly with the atmosphere, the huge energies involved in earthquakes are generated in, released in, and remain below the Earth's surface. Permanent surface manifestations of earthquakes (cracks or displacements) are uncommon except for the largest events, and are generally small and limited in scope, at least in terms of the scope of weather fronts moving across the Earth.


For a long time earthquake scientists have tried to find an association between earthquakes and syzygy (Solar and Lunar tides), but the correlation is just not there. Nor is there any apparent connection between volcanic eruptions and tides. Weather *IS* correlated with the orientation of the Earth's axis of course: when the north pole is oriented towards the Sun in the northern hemisphere summer, there is different weather than with the opposite orientation. Hurricanes and typhoons occur between June and November in the northern hemisphere, and the timing appears to be a heat latency effect. It takes awhile for the summer solar heat to accumulate in the upper ocean realm (water has a high heat coefficient, so it takes awhile to warm it up), and hurricanes derive their energy from the heat in warm ocean water. Hurricane Sandy was an unusual late-season event, because of the way pressure fronts interacted with each other to drive the storm backwards from the usual trade wind tracks and onto the New Jersey coastline.

Weather also correlates with the amount of CO2 and methane in the atmosphere, and also with the amount of energy that the Sun produces, but the critical geological record on the latter is distant in time and thus difficult to resolve clearly (see http://en.wikipedia.org/wiki/Snowball_Earth). Among scientists, the anthropogenic (human-caused) contribution to climate is now widely accepted as the evidence keeps piling up: the increasingly severe weather events of the past half century are caused in no small part by fossil fuel combustion. Of the hottest 10 years in the past century, 9 of them have been since 2000, and that correlates well with the growing levels of CO2 in the atmosphere. A good article to pursue this topic further is here:
http://en.wikipedia.org/wiki/Climate_change

Interestingly, methane is approximately 37 times more potent than CO2 as a greenhouse gas, and the amount of methane produced/converted by a single cow from the vegetation it eats is quite large. With the burgeoning human population and its increasing affluence, more people seek protein, and thus the number of meat-producing animals has skyrocketed in the past century. By itself this new methane is frightening. However, there is a huge amount of sequestered methane in what are called methane clathrates or methane hydrates - methane bound up in water ice beneath the ocean seafloors (see http://en.wikipedia.org/wiki/Methane_clathrate). This methane remains stable (and sequestered) as long as the pressure and cold temperatures around them don't change. However, with increasing temperatures caused by global climate change, it appears that these clathrates could become unstable, freeing more methane into the atmosphere, which will then get hotter, freeing ever more methane in a potential runaway feedback cycle.

Welcome to the increasingly interesting 21st Century!
~~~~~


Tuesday, November 20, 2012

Earthquakes: How Often?


Until the following question arrived, I had only thought of earthquakes as being relatively localized features, mainly occurring along continental margins and ocean-floor spreading centers or transform faults. The San Andreas fault is a mostly on-land transform fault. I hadn't really thought about how MANY earthquakes there are in the world as a whole.

Q:
Hello, I was wondering how many earthquakes happen typically in a year?
-Lauren J

A:

The USGS estimates that several million earthquakes occur in the world each year. Many go undetected because they hit remote areas or have very small magnitudes. The National Earthquake Information Center in Denver, CO, now locates about 50 earthquakes each day, or about 20,000 a year. There are far fewer large events than small earthquakes, and this website will show you how these are parsed out according to magnitude:
http://earthquake.usgs.gov/earthquakes/eqarchives/year/eqstats.php

There are lots of fascinating stats here, including an interesting table (below). Like asteroid impacts and frequency, or volcanic eruption magnitude and frequency, these all seem to follow an inverse log law:
The bigger the event, the less common it is.

Frequency of Occurrence of Earthquakes

MagnitudeAverage Annually
8 and higher
7 - 7.915 
6 - 6.9134 
5 - 5.91319 
4 - 4.913,000
(estimated)
3 - 3.9130,000
(estimated)
2 - 2.91,300,000
(estimated)


~~~~~

Saturday, November 17, 2012

Extinctions: Asteroid Impacts vs Volcanic Eruptions


The following question indicates that someone was thinking about things - a large step beyond just going to school and memorizing facts.

Q: 
Hello, I am 20 years old and from Portugal. My question arose when studying for school and noticing that these two events happen, more or less if it can be said on this matter, at the same time. Can a major impact like the one at Chicxulub have enough power to send shock-waves trough the mantel causing the major eruption at the Deccan traps? like if you "squeezed" the Earth and at its weakest point it broke, or like when you give a very strong hit on the top of the bottle and the bottom breaks away because of the pressure and strength that traveled until it finds a blockage it has the power to break through ... We know that earthquakes can be felt thousands of miles away but what happens inside the earth on the mantel at that time? If this is correct where would one get proof?
-Diogo C

A:

You have observed an interesting timing association that has intrigued geologists for a long time.

From Wikipedia (http://en.wikipedia.org/wiki/Deccan_Traps): The Deccan Traps formed at the end of the Cretaceous period. The bulk of the volcanic eruption occurred at the Western Ghats (near Mumbai) some 65 million years ago. This series of eruptions may have lasted less than 30,000 years in total. The original area covered by the lava flows is estimated to have been as large as 1.5 million km², approximately half the size of modern India. The Deccan Traps region was reduced to its current size by erosion and plate tectonics; the present area of directly observable lava flows is around 512,000 km2 (197,684 sq mi).

One website (http://palaeoblog.blogspot.com/2011/10/smaller-ka-boom-chicxulub-impact-did.html) offers this observation: "Researchers have simulated the meteorite strike that caused the Chicxulub crater in Mexico, an impact 2 million times more powerful than a hydrogen bomb that many scientists believe triggered the mass extinction of the dinosaurs 65 million years ago. The team's rendering of the planet showed that the impact's seismic waves would be scattered and unfocused, resulting in less severe ground displacement, tsunamis, and seismic and volcanic activity than previously theorized. "

Also from Wikipedia (http://en.wikipedia.org/wiki/Deccan_Traps) is even more specific information about the source of the Deccan Traps: "A geological structure exists in the sea floor off the west coast of India that has been suggested as a possible impact crater, in this context called the Shiva crater. It has also been dated at approximately sixty-five million years ago, potentially matching the Deccan traps. The researchers claiming that this feature is an impact crater suggest that the impact may have been the triggering event for the Deccan Traps as well as contributing to the acceleration of the Indian plate in the early Paleogene. However, the current consensus in the Earth science community is that this feature is unlikely to be an actual impact crater."

The short answer is that the Deccan Traps probably did not cause the extinction that wiped out most of the non-avian dinosaurs, though it may have contributed to making life even more difficult. There appears to be no connection between the Deccan Traps and the Chicxulub event.

On a related tack, the Siberian traps (http://en.wikipedia.org/wiki/Siberian_Traps) 250 million years ago may have contributed to or even caused the Great Dying, the Permian-Triassic extinction event, the most complete extinction event in Earth's history. More than 90% of species living in the Permian era abruptly disappeared at this time.
~~~~~

Wednesday, November 14, 2012

Coral Reefs as Resources


The US Geological Survey expends a lot of time and manpower on resource estimation: energy, minerals, biological (in several ways). The following question came at me sideways, and caused me to really think.

Q: 
What are some resources that coral reefs provide?
What are some topographical features around coral reefs?
- Maya R

A.
The main resources that coral reefs provide - that most people talk about at least - is biodiversity. This is a hard thing to quantify or explain, but if reefs all die from acidification and heat related to climate change, then much of the food-chain in the oceans would be severely disrupted. Some new drugs have already been derived from unique reef species, so that is another potential future resource. I believe that there are some entities that have mined reefs for the calcium carbonate that they contain, but this is like the Spaniards four centuries ago melting down precious Aztec and Incan gold artifacts. Trying to capture a "resource" this way destroys 95% of its value.

Coral can only grow where there is light, so this generally means the fringe waters of islands and coastlines, and only in tropical latitudes. In the Pacific, this often means that there are reef rings around volcanic islands or below-the-surface guyots. As the original core rocks of the volcanic island weather and crumble down, this generally means that the remaining topographic feature is an atoll: a coral ring with a shallow lagoon inside. There is very little topographic relief above the water line. The topographic fall-off of an island reef system tends to be steep, however. I've Scuba-dived some of these and the reef "wall" looks like it just goes straight down into the black depths. There are also reef systems on continental margins, and the Great Barrier Reefs of Australia and Belize are examples. Bathymetry tends to follow this characterization as one moves outward: the continental margin, then shallow water, then a reef system, than a steep fall-off to the continental shelves or in some cases the oceanic abyssal plain.
~~~~~

Wednesday, October 10, 2012

Rock Types


Rocks can be generally classified into one of three general rock classes. The first two of the three classes are easy to recognize:
1. Sedimentary rock, formed in layers by the accumulation of weathered rock fragments and/or chemical precipitates, usually under, or under the influence of water (and sometimes wind),
2. Igneous rock, which includes volcanic lava, as well as related (coarse-grained) intrusive rocks such as granite, diorite, and gabbro.
3. Metamorphic rock. This is generally more difficult to characterize and understand because it is modified – a derivative of - one of the other two.

About 90% of the queries we receive on Ask-a-Geologist, typically accompanied by a photo and asking "what is this rock", we cannot usually answer. In general, the photos have no scale and are blurry, and the light doesn't show the finer structures well. A geologist would want to turn the rock sample over in sunlight with a hand-lens, looking for mineral grains and their distinctive crystalline form or "habit", and perhaps scratch visible crystals with a knife-blade to check their hardness to aid her identification effort.

The following is a rare case of a query accompanied by a good quality photo (it even had a coin to provide scale!) and enough additional context information to allow me to identify the rock.

Q:
Last weekend I climbed Mount Mansfield in Vermont. The higher we got, the more silvery the rocks looked. Attached is a picture, but it doesn't really do justice to the silvery tone. My friend wanted to know what caused the rocks to look so silvery.  I said I'd ask the expert.
--Valerie W
Photo: Yannick Guenet

A:
That's a schist. As in, that's a Gneiss Pile of Schist.  ;=)

Bear with me here – there is a point to this.

The silvery-ness that you see is caused by metamorphism, that is, a change to the character of the rock and its inclusive minerals. The word derives from metamorphosis – literally, change of form. Metamorphism usually is caused by the original igneous or sedimentary rocks being buried by tectonic forces at some time in their ancient past, but it could also be caused by hot fluids from a nearby heat-source (like an intruding granite body). Old-time miners would say that metamorphic rocks had been “stewed and cooked” – which is remarkably prescient.

The deeper a rock is buried, the greater the consequent increase in pressure - and also temperature – that it will experience. The photograph shows a complex rock that under great pressure has been deformed plastically – in this case, it is a schist. According to several sources (here's one: http://en.wikipedia.org/wiki/Blueschist ) this means depth of burial at one time reached 15 - 30 km before it was uplifted by tectonic processes and then exposed by weathering. The result of this high pressure/high temperature transformation process is that the original minerals are converted into several new minerals in a schist, commonly including glaucophane and muscovite - the latter is usually called white mica. Typically, there is plastic flowage going on, which leads to the alignment of the glaucophane and muscovite in the flow direction - and you can see this in your photo. The muscovite in these rocks, however, is usually very fine-grained - sometimes not easily visible even in a hand-lens. The net effect is to give the rock an over-all glossy look, and if you ran your hands over it, a slightly greasy feel sometimes. By the way, there are blueschist (blue-gray in color) and greenschist varieties of this rock. The latter are prominently greenish in color, because this kind of schist is loaded with chlorite and epidote: green, chlorine-rich minerals both derived from original black minerals such as pyroxene, and dispersed throughout the resulting rock as a whole by the metamorphic (“stewing and cooking”) process.

You describe the rock becoming more silvery with increasing elevation. That could be because the entire mountain is upside down from its original emplacement, and as you rise in elevation you are in fact walking deeper in time and burial depth. While this sometimes happens during tectonic processes, it is not very common. Though it seems more deformed, I suspect that in fact you are seeing a gradational change from an even more strongly metamorphosed rock, called a gneiss, found at the lower elevations of your hike. This kind of rock doesn’t have the muscovite “sheen”, but instead is typically devoid of chlorite and platy minerals. Gneiss commonly has much larger crystals - this is because the rock was so hot, and maintained for such a long time a great depth of burial, that everything re-crystallized. The longer a hot, fluid mush is held in place, the larger the crystals can grow. Gneiss is typically formed at 15-50 kilometer depths. I suspect that the original rock mass is still upright, and that you were in fact climbing up from deeply metamorphosed gneiss to less-metamorphosed schist above it.

~~~~~

Mount Lemmon is a spectacular uplifted mountain range located far to the south and west of Mount Mansfield - it lies just north of Tucson, Arizona. From the city, the face of the mountain has the broad texture and layering of the original sedimentary rock that it was made out of. However, up close it is coarsely crystalline and very much NOT (any longer) a sedimentary rock. As you move farther north in that complex you are moving ever deeper in original burial depth, and the gneiss turns gradually to granite – back to an original plutonic form. The original sediment probably was weathered out of a nearby, much more ancient granite complex. There is a famous story of a PhD student (Dr. Ed McCullough, who eventually became the geology department head at the University of Arizona) finding a blastoid (head) of a Paleozoic crinoid in the metamorphic rock while mapping the complex with other faculty. This story – and Mount Lemmon - neatly tie all three rock types together in one package.

~~~~~



Friday, July 20, 2012

Tsunamis, Rogue Waves, and Tidal Waves


Geology started out as the science of uniformitarianism: What we could see in the rock record is what we could expect to see in the future. The initial assumption of Lyell and other early geology pioneers was that the “Great Flood” of the Bible was not to be taken seriously, and that every geologic phenomenon in the past was like what we observe today: calm and steady and slow – like weathering.  However, in the past several generations, geologists have come to recognize that there have been short-lived, phenomenally catastrophic events that have changed the face of the landscape. One of these is the tsunami, a word of Japanese origin where it was first described scientifically. The word was chosen about a generation ago to distinguish one kind of wave event (a tsunami) from a tidal wave or a hurricane storm surge. A tidal wave is a twice-daily feature associated with Lunar and Solar cycles. In Southeast Alaska and the Bay of Fundy in eastern Canada, these can reach 15 meters in height – especially if focused into an east-west-oriented narrow bay or fjord such as at Fundy. A “tidal bore” is a wave that moves in with a rising tide, and in shallow estuaries like Turnagain Arm in Southeast Alaska, these can be walls of water several meters high – sufficient to overturn or “pitch-pole” a medium-sized boat.

Q:
What causes tsunamis? Can one happen in the US?

-Jared W

A:
There are four different kinds of events that have caused tsunamis in the past:
1.       Asteroid impacts. There are huge tsunami deposits on Haiti stemming from an asteroid impact 65 million years ago.  This was the dinosaur-era-ending Chicxulub asteroid, which impacted on what is now a small village of that name on the northern tip of the modern Yucatan peninsula of Mexico. Fragments of this explosion apparently also went sub-orbital and landed as far away as Montana and the mid-Pacific ocean. Estimates of a mega-tsunami wave in the Caribbean up to 3 kilometers in height have been suggested – enough to completely inundate a large island such as Madagascar.

2.       Landslides. The face of a mountain fell off into Lituya Bay in southern Alaska in 1958. It created a wave at least 500 meters high, judging from surrounding mountains stripped of trees to at least that elevation. Surviving witnesses describe their vessel being floated over a large raft of logs, and the modern coastline remains largely denuded. http://en.wikipedia.org/wiki/Megatsunami

3.       Volcanoes. When the volcano Krakatau exploded in 1883, 45-meter-high waves reached as far as 10 kilometers inland on Sumatra, and swept people, animals, and debris back into the Sunda Strait. More than 36,000 people died in this event, and contemporary descriptions report that a person would walk across the Sunda Strait on bodies and logs without getting their feet wet. http://www.csmonitor.com/World/Global-Issues/2010/1028/Japan-tsunami-is-small-compared-to-five-of-world-s-biggest-tsunamis/1883-Krakatoa-tsunami The tsunami from the catastrophic eruption of Thera volcano (modern Santorini in the Aegean) 3,500 years ago apparently ended the Minoan civilization on nearby Crete. The language of modern science is substantially Greek-based (with Latin) as a result of that single event.

4.       Earthquakes. In January 1700 AD, a subduction earthquake in the Cascadia region of northwestern North America sent a tsunami across the Pacific Ocean that devastated villages on the Sendai coast of Japan. The earthquake sunk a forest in Puget Sound below sea level. The wave that reached Japan was called the “Orphan Tsunami”, since it was not associated with any locally-felt earthquake or typhoon – it arrived without warning under a clear blue sky. In 1946 a subduction earthquake off the Chilean coast of South America caused what one geologist friend referred to as “unplanned urban renewal” many hours later in Hilo, Hawaii. I have personally seen signs marking the wave run-up on telephone poles 5 meters above my head in the modern downtown area. The Great Sumatra Earthquake of December 2004 killed over 250,000 people from Indonesia to India. The wave reached Sri Lanka many hours after it was initially triggered, but there was no infrastructure in place at the time to warn the millions of affected people in its path. The Great Tohoku Earthquake of 2010 triggered a tsunami that devastated northeastern Japan, directly led to a melt-down at the Fukushima Dai-Ichi nuclear plant - and destroyed docks and ships many hours later on the Oregon coast.


It is important to understand that relatively few earthquakes cause tsunamis. The basic requirement is that the causative fault must have a normal or reverse component to it - part of the seafloor must drop or lift suddenly. Modern tsunami warning systems are based on a two-tiered approach: an initial earthquake beneath an ocean floor or ocean margin is detected. If the fault system is well known (for instance is understood to be a subduction fault), then an initial warning is issued. Deep ocean buoy systems are then monitored – these waves may travel at more than 500 kilometers per hour, so they take a relatively long time to cross an ocean. If a wave-front is noted passing through this system, then warning sirens light up on the threatened coast. http://en.wikipedia.org/wiki/Tsunami_warning_system


Technically, hurricanes (Atlantic Ocean) and typhoons (Pacific Ocean) do not cause tsunamis, but they DO generate low-pressure-driven storm-surges that could top 10 meters above normal sea level in the worst cases. These are not sharp-edged waves like a tsunami, but instead are long-wavelength, very broad surges of seawater tracking the eye of the hurricane or typhoon as it hits land. Hurricane Katrina in 2005 did most of its damage with a huge storm-surge that overwhelmed the levees and barriers designed to protect New Orleans, a city that over time since its founding has sunk below sea level.

There is another class of large water waves called “Rogue” or “freak” waves. There is a long history of “disappeared” ships in the history of humankind, and anecdotal stories of waves exceeding 30 meters in amplitude that somehow left survivors. Recently, sea-height-measuring radar satellites have allowed this sort of feature to be quantified. The physics concept of constructive interference of waves comes into play, but there may also be other factors involved, including diffractive focusing and non-linear effects. For instance, the southwest-flowing Agulhas current in the western Indian Ocean has long been known to interfere with westerlies to create a zone of dangerous rogue waves of unusual frequency and intensity.  http://en.wikipedia.org/wiki/Rogue_wave

By the way: that Biblical story of the Great Flood? As scientists we must be careful and not just dismiss something out of hand - like this one was. Geologic evidence now suggests that the Black Sea was a continental basin that flooded catastrophically around 5,600 B.C.E. 

~~~~~

Wednesday, July 4, 2012

Get the Data. Don't get Killed


There are different risk-factors that come with different life-callings:
  • Fish for King Crab in the Barents Sea: get rich fast, but unusually high risk of becoming crab food.
  • Transport cocaine from Colombia to Texas: get rich fast, but unusually high risk of being beheaded.
  • Fight forest fires: unusually high risk of joining the Bar-B-Que and burning with the trees. Not even health insurance until next year.
  • Work as an accountant: Live Long and Prosper!
There have been several questions directed at us in Ask-a-Geologist about safety while working as a geologist or geophysicist. These increased, as expected, during the 2004-2006 eruption of Mount St Helens. To a previous question, I mentioned walking out the leading edges of moving lava flows in Hawai'i. This was not done casually, but to gain a clearer understanding of how these flows move - and why they suddenly can inundate towns like Kalapana. If we understand in a statistically reliable way how lava creates its own new topography, perhaps we can predict where the Danger Zones are. 

This has non-trivial real-world consequences: if you build in Zone 1 or Zone 2 on the Big Island, your home-owner's insurance will be phenomenally high - if you can get it at all.

In a larger sense, however, this opens the broader issue of inherent risk that comes with certain jobs - and how you can manage those risks.

In 1977 a young USGS geologist named Cynthia Dusel was part of a mapping team, surveying the Big Delta Quadrangle in east-central Alaska, when she was attacked and mauled by a bear. She survived, but lost both arms. Since then she has married, had a son, and even served as acting chief of the Western Mineral Resources team in Menlo Park, CA for a year. She's something of an icon among us in the USGS: very matter-of-fact about her disability, very upbeat, great sense of humor - and epitomizes indomitable courage. 

The response to that attack within the USGS was probably predictable: everyone going up to work in Alaska started packing huge guns. Then the scientist part in the Survey scientists woke up and many of them thought about it a bit more. Let's gather data about the real threats to geologists working in Alaska! they said. They did... and were surprised to learn that bear attacks came in as Number 7 on the list. Shooting yourself with your own weapon came in Number 3 - I once watched a rettle tech shove a cocked .357 Magnum into his holster. This led to the development of a sophisticated 3-day weapons safety training course (informally called the "Bear Blasting" class, of course) required of anyone planning to work in Alaska. The Number 2 killer of geologists working in Alaska was helicopter accidents - my first USGS boss was killed in Ketchikan harbor this way. And this led to careful "carding" of pilots and aircraft, and mandatory training of geoscientists. None of us ever worked with a pilot with less than 5,000 hours of flight experience, and we always wore NOMEX clothing and $1,500 fighter-pilot helmets, among other things.

The Number 1 killer of geologists was drowning. That's right: drowning. If you fall into deep water in Alaska (and southeast Alaska and the Aleutians are mostly islands, anyway), your arms will essentially stop working after about a minute unless you are wearing a Mustang suit. That's hypothermia for you. I came within a hairs-breadth of becoming one of those drowning statistics in Klawock in August of 1995.

It became a growing part of our evolving scientific tradition: we all loved working in the field, but it carries with it different dangers. Soooo... how can we minimize these? How can we manage these risks?

Q:
That's a pretty crazy account.  It's particularly funny to think about your work when I think of it in comparison to our OHS (occupational health and safety) officers who come around to inspect our offices periodically to make sure that our chairs are properly aligned to make sure that we don't hurt our backs by sitting all day long.  Why in the world would you be stomping around an area of jungle amidst fresh-flowing lava?  - Lisa W.

A:
Throughout my professional career I've faced many rather disparate dangers. This wasn't done for the adrenaline thrill - it's the only way in most cases to acquire the crucial data that we need to solve real world problems. In the Continental US, this usually means working in really rugged terrain. I camped overnight with a geophysical crew inside the crater of Mount St Helens in 2007. I had helicoptered in with some geophysical equipment, but after several days had to get back to the office before the end-of-week scheduled helicopter flight. A case in point: I planned for it, and walked out. However, it proved to be far more rugged terrain than I had anticipated in my planning (which was done with 10-yr-old air-photos in a terrain that is unconsolidated, and evolving nearly every day). If I had not been carrying (and using) hiking poles with my pack, I wouldn't be wearing these front teeth today. I still sustained permanent damage to my left big toe and my right knee in the ~20 km walk-out (the knee is still swollen as I write this).

In Venezuela, my personal journals have WAY too many "I was nearly killed again today" entries. That was the first time I really looked at the full array of danger that comes with working in the deep jungle. Initially we went down for a three-year assignment to map the roadless, jungle-covered southern half of Venezuela thinking the the big risk was from snakes. In fact, I encountered a Bushmaster on my very first Entrada. It took awhile to recognize the more subtle, even hidden dangers: testosterone-poisoned pilots, poorly-maintained helicopters, Chagas disease, piranha in all the rivers, etc. The Number 1 killer? The Anopheles mosquito - the vector for Plasmodium Falciparum, also known as cerebral malaria, followed closely by drunk drivers. I lost two of my best friends in Venezuela, in separate incidents, to drunk drivers.

After a series of very close calls I took the Advanced Trauma Life Support training at the University of Maryland medical school (yes, it's supposed to be for medical doctors - but I have the certificate to prove it). I discussed the issues with some more experienced field geologists and began instituting some safety protocols for the mapping mission that I was in charge of - for instance we almost never used helicopters after the first year there. We wore light-colored clothes to minimize being targeted by Africanized bees. We always walked the picas (trails) in pairs. We always insisted on mosquito nets surrounding our hammocks, etc. One of my colleagues instituted one safety protocol himself: he bailed out, breaking his contract and leaving his commitments on my shoulders. I've never begrudged him for this by the way: he was one really, really frightened dude. A year later he even left the geosciences profession, abandoning his PhD training, to become a financial advisor. Live long and prosper.

But here's the thing: you CAN control the variables, you CANpush the statistical envelope far over to the likely-to-survive side of the Gaussian probability curve. 

I took some training last year that is a case in point. You can't study a volcano unless you can get a lot of equipment up INTO it. My sons will attest that just getting 300 kilos of gear up into the Pumice Plain (the Mount St Helens Blast Zone) for their mom's Masters Degree research project was a non-trivial exercise. It's much harder to do this in the upper edifice of the volcano - so we use helicopters.

Easy to say, technically hard to do.

The safest way to ensure the survival of the helicopter and pilot is NOT to have a lot of loose shovels, antennas, and batteries INSIDE the ship. This little nugget of wisdom was culled by carefully gathering reports of all helicopter crashes in the United States over 50 years. Instead, you *sling* all that loose, sharp-edged junk. There is an electrically-controlled hook on the belly of most helicopters. We took a full day to practice this routine on a level lawn:
  • Gather all your gear in a pile, weigh it piece by piece. Give that manifest to the pilot - who will do a calculation to see if he can even lift it to the elevations you will work at AND have enough margin to carry you along with it.
  • Load it into a net that itself weighs 25 kg. Try to balance that net, arrange it so things tilt inward, and especially be sure that nothing is sticking out of the net that could tangle with anything - like you, or the skids.
  • Then call the helicopter in to you, holding your hands up and out in the direction of the wind (we usually dangle a strip of red flagging tape so the pilot can judge the local wind velocity).
  • As the ship approaches, it comes in slowly at about 1.5 meters off the ground - remember that the thing is wobbling around in the wind as the pilot tries to control it against the volcano-heat-triggered turbulence, and it is SCREAMING SO LOUDLY that you can easily get rattled just by the 140-db sound (we wear helmets with ear protection, but it's still unnerving).
  • You must then walk under this shuddering, screaming thing, hook your sling net to the belly, and then carefully back out (NOT turn around), without tangling your feet in the net, and keeping your footing amid the rocks and talus.
  • Above all, if you stumble, you must NOT grab one of the skids to regain your balance. If you do, the ultra-light craft will flip, the blades will hit the ground, and all that angular momentum must go somewhere really, really fast – and you will both probably die. You have to trust the pilot, and he must trust you: if you hook the net wrong, or inadvertently tangle it in one of his skids, it could kill him. The craft is so fragile that you can literally push it around in the air above you with your hand... but those screaming turbines mean it is powered by 600 horses. Everything spinning is so finely balanced that if a blade nicks a branch it will chip a chunk off – and it then becomes hugely unbalanced. Then the angular momentum comes into play, and the aircraft will literally beat itself (and its occupants, and everyone within 20 meters) to death.
When a helicopter goes down, that's just the beginning of the bad stuff... think of the old high-school joke: What's red and green and goes round and round real fast? A frog in a blender. Now imagine doing this sling exercise on a steep ridge with 30-knot wind gusts.  THAT'swhy we practice and practice all day long on a lawn to do this right. So it's reflex. So when the brain starts mis-firing, you STILL do the right things.

This is basically how I teach Jujitsu to my students, by the way. No one ever defended themselves from their Worst Nightmare by using their cerebral cortex - it only works from muscle memory: reflex.

Live Long and Prosper. And still enjoy the Adventure!
~~~~~


Tuesday, June 26, 2012

Water and Specific Heat Capacity

It's not a coincidence that about 80% of the human population lives within 60 miles/100 kilometers of an ocean margin. Spend a winter (or a summer) in an interior state like Kansas, or Kazakhstan, and you will understand why they are not crowded. Temperatures in Fairbanks, Alaska, can range from 86F/30C to below -60F/-50C between Summer and Winter - and that's above the Arctic Circle! I've personally experienced temperatures of 130F/50C in Arizona and 142F/61C while working in the interior of Saudi Arabia.

We would have occasional snows (and freeze rain) when we lived in Virginia. That wasn't so bad... But sometimes we do not even see snow during the winter in Vancouver, and it's notable when the temperatures get much above 75F/24C.

I could easily get used to this. I think I'll stay...

There's a downside to this, of course (there always is, isn't there?). Populations close to a seashore are much more vulnerable to a tsunami from a seafloor fault rupture - or an asteroid impact in the ocean. Volcanoes can even figure into the Coast is Toast picture: the tsunami that resulted from the explosion of Krakatau in 1883 traveled more than 10 kilometers inland onto neighboring Java and Sumatra islands... then swept everything it had picked up and took it all back out to sea. Contemporary accounts mention being able to walk across the Sunda Strait on logs and bodies without getting your feet wet.

There is a reason for that very human tendency to hug the coast, and it's not for the sandburgers and grit-flavored potato salad. It's because of the moderating effect of nearby oceans. The key to that effect is the specific heat capacity of water - it is more than 4 times greater than air. In other words, it takes more than four times as much energy to increase a unit mass of water by one degree C than it does to raise the same mass of air by one degree. That means that the oceans act like a thermal buffer - because they can absorb and release so much heat without much of a temperature change.

Bottom line: ocean temperatures don't change much.

We notice the effects of water on temperature in a number of different ways, and the next series of questions raises an unusual issue:

Q:
Does an object traveling under water get colder as it increases it speed through the water? Similar to a wind chill factor. 
- Gaylord M.

A:

Yes - if the water is colder than the object moving through it.

Water has a specific heat capacity of 4.2 with respect to air. This means it can hold - and transfer - far more energy than air for just one degree of raised or lowered temperature. The faster you move through a medium (like water) that has a different temperature, the faster and more effective is the thermal exchange, all other variables being constant.

Most people know that getting into cold water will chill them much faster than walking through air of the same temperature. I noticed when I lived near the Red Sea that if I went diving in temperatures below 82F/28C, that I would quickly become hypothermic. This hugely different heat capacity is also why it is so important to wear clothing that keeps moisture away from your skin as much as possible.

Q: 

Thanks for the reply. I asked the question, as I was wondering if it could have had an effect on the Titanic's rivets to cause them to fail. I had watched a segment on the History channel where they had ran some tests and determined the rivets had not failed. However they were running their tests in what appeared to be a normal environment. Only one of the test rivets failed.


A: 

The possible effect of ice-temperatures on the Titanic's rivets is an interesting thought. I'm not a metallurgist, but have watched, with interest, several back-and-forths in the semi-scientific literature about the possible "failing Titanic rivets" issue.

In this case I don't think the temperature would have made much difference, because North Atlantic water ranges between 0C and 22C, depending on the month.

That's not really much of a temperature difference, considering the temperature that the rivets were forged at, and the fact that the ocean temperature cannot go below the freezing point of ice. Because of water's large specific heat capacity, there really is not much of a temperature change in the North Atlantic.

There were literally thousands of steel-riveted ships plying the North Atlantic during that epoch, and it makes more sense to worry about metal impurities in a given production batch of rivets than in the narrow temperature range that they would operate under.
~~~~~








Friday, June 22, 2012

Infrasound


The Earth really is a living thing in many senses of the word. For instance, it is very active – it even makes sounds.

Q:
Hi, Wondering what kind of sounds the inner earth makes? Do you know where I might go to hear this?
Thank you 
-Nathan W.

A:
There are sounds from the "inner Earth", but they are generally at frequencies below what the human ear can detect - this frequency range is called "infrasonic". Occasionally these can be heard, but not normally.

I once heard a recording from a seismometer located on Tungurahua volcano in Ecuador - but it had been electronically speeded up about 400 times to bring the signal up into the audible range. It sounded like a large animal moaning and roaring. This of course would be normally inaudible to the human ear.

Here is one somewhat different, for volcanic gas venting: http://volcano.oregonstate.edu/vwdocs/videos/siocomm.mov 

Here is an example of the sounds of an actual surface eruption at Tungurahua: http://en.rian.ru/video/20101202/161596301.html

Note that if the volcano is not actually erupting at the surface, the sounds made are almost always inaudible (infrasonic).

More volcano sounds can be heard here: http://volcano.oregonstate.edu/book/export/html/385

In some volcanoes there is a seismic signal detected called "harmonic tremor" - it is generally thought to be caused by fluid movement through conduits deep below the volcano, and sometimes is a portent of an impending eruption (Mt Pinatubo in the Philippines in 1992, for instance). Harmonic tremor is typically in the 2 Hz frequency range - well below the lowest frequency that a human ear can detect (which is about 20 Hz).

Earthquakes (shifting, sliding crustal plates) also generate seismic waves, but like those under a volcano they tend to be mostly at frequencies well below what a human ear can readily detect.
~~~~~

Tuesday, June 19, 2012

Geoengineering


Geoengineering is a very broad topic – in fact, no one group of people can actually agree what the word actually encompasses. One thing for sure, however: the word carries with it a lot of emotion already, not unlike Fracking.

Q: What is geoengineering and why do people say it is bad?
- Byron S.
A:
The term “geoengineering” (or environmental engineering, depending on who you are listening to) can encompass a lot of very different things: 
  • Stratospheric Particle Injection for Climate Engineering (SPICE). This experiment this Spring in the Europe envisioned injecting water into the atmosphere at a 1-kilometer altitude. However, there have been proposals to inject vast quantities of sulfates into the stratosphere to reduce global warming. The theory underlying these is that Mt Pinatubo already did this in 1993 – and lowered the Earth’s average temperature by more than a degree C for two years.
  • Injecting large volumes of iron sulfates into the Southern Ocean in 2009. This was done to test a theory that adding iron to the ocean would encourage phytoplankton growth, leading to an increase in zooplankton growth with concomitant oxygen release and carbon dioxide sequestration all at the same time. The fear, of course, was that the exercise would trigger a massive, toxic algal bloom.
  • Injecting water from a hose maintained at a 1-kilometer altitude to test if this could cause more reflectance of solar radiation, and thereby reduce global warming effects.
  • All the Walmart parking lots in the world contribute to large-scale diversion of water from the Earth and unusual absorption of solar radiation, creating unnatural microclimates (“heat islands”) that will affect local and even regional weather. In fact, one can watch any local regional weather radar, and readily see that clouds will often form donut holes over large, paved metro areas like Portland, OR.
  • Groundwater depletion and other anthropogenic (man made) changes in terrestrial water usage were responsible for about 42% of the 8-cm rise in global sea level observed between 1961 and 2003.
  • Ethinyl Estradiol (EE2) is the active ingredient in birth-control pills. More than 100 million women worldwide use contraceptive pills, and the products make their way through waste-water treatment systems into rivers and lakes, where they have caused widespread disruption of aquatic environments. It has done this by disrupting endocrine systems in wildlife (for example, irreversible development of eggs in the testes of male fish, a condition called “intersex”). EE2 introduced into a Canadian lake in 2001, at a level of only 5 parts per trillion, caused the population of one fish species to completely collapse.

There are other potential kinds of geoengineering, limited only by the creativity of people who worry about the Earth we live on - and who DON’T worry about where funding for their proposals might possibly come from.

These mega-scale engineering changes all sound like good ideas – they promise potentially great (and highly leveraged) rewards. The problem with geoengineering, according to a lot of people, is that if we play with our ecosystem on broad scales like these, we can never be sure of the consequences.  We may very well, with the best of intentions, create a spiraling-out-of-control disaster. We could just be asking for it.

An extreme example of this fear was the concern that when the Large Hadron Collider in Europe went online, its huge particle beams would create a tiny Black Hole - that would burrow to the center of the Earth and destroy our planet from inside out. The most compelling argument against this, of course, is that far greater particle energies are generated daily in our upper stratosphere by cosmic rays… without any noticeable harm having been done over the past 4.5 billion years or so.

Another example of mega-scale engineering is the massive use of DDT to solve a perceived insect problem – to save crops and mitigate human disease by eliminating dangerous insect vectors. We now know, of course, that the extensive use of DDT did solve, at least temporarily, some crop and human disease problems. However, it had huge unforeseen downrange consequences like plummeting bird populations and possible birth defects.

Some people might call the massive use of antibiotics another example of a well-intended global effort to deal with a human problem – but one that has in fact led to a growing disaster. We now see explosive growth of Multiply-Resistant Staphylococcus Aureus (MRSA, or the terrifying “flesh-eating bacteria” increasingly in the news). Indiscriminate antibiotic use has also led to a world-wide resurrection of resistant tuberculosis, Bubonic Plague, and other once-curable diseases.

Perhaps even more terrifying is the research into genetic engineering: what if something unforeseen gets loose into the world’s environment, with disastrous and irreversible consequences, like Zebra Mussels, lampreys, and Asian Carp getting into the Great Lakes? Or Kudzu being introduced into the southeastern US? Or Africanized bees introduced into the Western Hemisphere? Or cases of incurable cerebral malaria exploding in areas where unregulated hydraulic mining is rampant?

In 2010, a gathering in Oxford, UK, came up with some guiding principles for geoengineering:
-          Geoengineering should be regulated as a public good
-          There should be public participation in decision-making
-          Research should be openly published
-          There should be independent assessments of potential impacts
-          Decisions to deploy any new technology should be managed within a “robust governance framework.”

All of these principles sound great – but are terminally vague. Furthermore, they will probably never be implemented on an international scale. It takes just one nation ignoring the International guidelines on something as far-reaching (and frontier-crossing) as geoengineering to abrogate the whole effort for the rest of the international community.

If there is a lesson here from the pesticides, antibiotics, and biological introductions, it is that nothing is consequence-free. However, many people feel that they are forced to just stand by and helplessly watch things unfold - decisions made by just a few people. That may be why there are such vociferous demonstrations to something as innocuous-sounding as SPICE.
~~~~~

Saturday, June 16, 2012

Black Holes & Supernovas & Geology


Here is a continuing question from 3-yr-old Samantha. It actually goes to the heart of why we have geology in the first place: black holes and supernovas of earlier suns have led to a cyclic mix of fusion-created heavy element products like oxygen, carbon, iron, and silicon - major constituents of our rocky Blue Marble, water-covered planet. A world like ours could not have existed in the early life of the universe.


Q:
Thank you so much for your reply. She (Samantha) still talks about you from time to time. Then out of the blue she asks "Mommy, what are black holes made of?" I don't know! :)
--Jo L.

A:
Well, the short answer is a LOT of mass. There are actually at least two different kinds of Black Holes.

A Stellar Black Hole starts with the collapse of a very large star - a star much bigger than our Sun. As the star uses up its hydrogen by fusing it to helium, it starts converting helium to carbon - these stars are a deep red, almost garnet color in a visible light telescope. Rather quickly on a cosmic time-scale, it will start converting carbon and helium into a number of other life-critical elements, all the way up to iron. The fact that the Earth's crust contains elements up into the uranium range suggests other processes, too. All the material we find on our own Earth has come from this thermonuclear process - probably from many ancient stars that reached old age and blew up long ago.

In two words, we are “Star Stuff.”

Somewhere in this winding-down process for this very large, earlier star, there is an initial collapse of the outer blanket of hot gas material down to the star's core, and a "bounce" causing an initial huge blow-out of the outer envelope. This is called a nova, or in some cases a super nova. It produces prodigious, short-lived amounts of radiation from visible light all the to X-Ray energies and beyond. In a distant galaxy, a supernova can look temporarily like a nearby star in our own galaxy.

This outer shell ejection process creates something called a Planetary Nebula - a glowing shell of gas that almost looks like a planet in a cheap telescope. Finally, there is a huge terminal collapse and all the remaining matter, without thermonuclear heat to hold it up, collapses into what becomes a Black Hole. It's called a Black Hole because there is so much mass in such a tiny volume that it bends light. It bends light so strongly - this is an essential part of Einstein's General Theory of Relativity - that light can't get out of a certain volume outside the central concentrated mass. This "edge" where light can't escape from is called the Schwarzschild radius, or the Schwarzschild discontinuity. You can guess who suggested this idea first. If the original star isn't big enough, the mass will collapse back into a White Dwarf - or if there is more mass, it will collapse into a neutron star, a teaspoons of which would weigh tons on Earth (if you could get it here or even weight it).

This is a description of a multi-stellar-mass Black Hole

There are other, far larger Black Holes. Galactic Core Black Holes are found in the centers of most galaxies including our own – and they form for different reasons and are HUGE. These Black Holes result from too many large stars in the crowded center of the galaxy being in too small a confining space - and they coalesce into each other forming a Black Hole that grows ever larger with time as it gobbles other nearby stars spiraling into it from tidal orbital collapse. In some science fiction books this is called "The Eater" or the Black Monster. We know there is a Galactic Core Black Hole in the Sagittarius constellation - the center of the Milky Way galaxy - because astrophysicists can see huge Doppler shifts in radiated light over a very small angular separation in a tiny area. This zone was originally named "Sagittarius A" - for the first apparent brightest star classified in that constellation by early astronomers. Sensitive satellite detectors indicate that the center of this interesting area radiates light all the way up into the X-Ray range of energies. On one side the Doppler shift indicates that material is rotating TOWARDS us (the absorption bands are blue-shifted), and close by on the other side there is a red shift telling us that it is rotating AWAY from us. The latest indirect calculations suggest this area, called Sagittarius-A* (Sagittarius-A-Star, or "Sgr-A*" for short) is about the diameter of Mercury's orbit around our Sun - but holds a mass equivalent to at least 44 million Suns in that relatively tiny volume. It's hard to see this, as the whole mess is about 26,000 light years away from us, so it's taken some very clever astrometrics by some very smart astrophysicists to get these numbers.

~~~~~

This seems like more than a normal 3-yr-old might be able to absorb. I am struck, however, that this 3-yr-old of yours has such a wide-ranging interest in scientific things. She could not get there without a highly supportive parent who will spend the time at least trying to answer her questions. You must have some rather eclectic conversations with your daughter.
~~~~~

Wednesday, June 13, 2012

Age Dating – and Why it is VERY Important


We have received many queries that implicitly ask a question about how old something is – typically the odd rock that they found in their backyard. A review of age dating, and why it can be critically important, seems appropriate here. 

Q:  
How old is this rock?
- various 

In 1979, a young USGS geologist named Rick H. was mapping flows on the north flank of a beautiful, glacier-covered, symmetric volcano in southwest Washington State. He had some idea of how old the Goat Rock Dome was that he stood on – textures and some sparse historical information suggested that it was very young. He had no idea that in a year the huge outcrop he stood on would be moved many miles to the north – that the spot he then stood on would be more than a thousand feet up in the air. The 1980 eruption of Mount St Helens killed 59 people – that is, that authorities are certain of. The death-toll could have been greater by more than 800 people. By a miracle of governance, those people were being held back at a roadblock until 9am on May 18th. However, 45 minutes before the gate would have been opened - to allow in people who had property around the volcano - the monster blew up catastrophically with a lateral blast. Authorities were certain of 57 people killed, but speculate that there were more caught in the blast that no one knew about. Gray dacite dust fell on cars in Atlanta a day and a half later. 

As the new chief scientist for volcano hazards, I made a point of visiting - and spending time listening to - every single staff member scattered over six different centers. This was not a trivial exercise; it meant lots of airport time and lots of listening. I made a point of spending the same amount of time with the technicians as I did with the senior scientists, and this helped me get a better view for how things were really working within the organization that I had just inherited. In one case, techs clued me in that one of our observatories was no longer functioning, due to a perfect storm of very human conflict starting with a management failure.

The experience was not all grief, however. One of the people I spent time listening to was Andy C., a brilliant young PhD geologist/geochemist who had decided to specialize in age-dating. I also talked with Jim S., a smart, furiously hard-working tech who worked with him. After listening to them, I travelled to the USGS national headquarters in Reston, VA, and tin-cupped around the building. I mean this literally – I carried around a tin cup with me to help break down resistance by disarming people with humor. I was looking for “spare change” in people’s budgets that I could divert to Andy’s laboratory. Spare change in my little 120-person volcano science team usually meant a few thousand dollars from my cost center budget. Two thousand dollars would pay for a young scientist to attend a science meeting, where he would not only learn what was going on in his field, but connect with people he could cooperate with. This meeting attendance had the effect of leveraging our meager funds to accomplish quite a bit more with them by getting others to help us accomplish our objectives.

To put this in perspective, a Stryker combat vehicle costs about $1,500,000. For the Department of Defense, however, I was looking for funding down in their noise-level. For them, our needs were what Sherrie G., a DOD executive, dismissed as “decimal dust.”

But Andy had both energy (he frequently worked 60-hour weeks) and a vision. His vision was to create a center of excellence: a laboratory for high-precision dating. I found and funded him with $250,000 to develop the world’s best state-of-the-art 40Ar/39Ar age-dating laboratory. This has allowed him to steadily refine the ages of very young volcanic rocks, which in turn allows us to put better and better parameters on the eruptive frequency of volcanoes – so we know what we may or may not have to worry about.

In the 10 years that followed, Andy had accumulated a sufficient number of very good age-dates that he was able to start looking in broad brush at the eruptive history of the entire Cascades range - and he can now see episodic pulses of eruptive activity in the past 500,000 years. Importantly, this includes the first hints that we are entering into an unusual period of volcanic activity right now.

In the past 5 years, Andy refined his +/- errors on an age-date from several thousand years to just 400-500 years. He did this by gaining precise control on the atmospheric Argon component in rocks, but also by refining his sample-collecting techniques. He sought the centers of lava flows, parts that were “platy” because they were shearing as they cooled while still flowing. He also avoided porphyries, because the internal crystals formed under different circumstances than the fine-grained that had extruded out onto the Earth’s surface. Other things he avoided included air-vesicles and glass: that is, water-quenched lava that inevitably had an Argon contribution from the water. How did he sort these out? By licking the rock with his tongue. If his tongue stuck slightly to the rock, experience showed that he would get a low-precision date on it. Since he was working long hours to deal with a huge back-log of samples, this kind of “pre-sorting” had gone a long way toward narrowing down his error-bars on dates.

So..... How Does Age-Dating Work?

Wait, you ask, how does age-dating work?  In the pre-radioactive isotope days, crude dating could be done by measuring how fast sediments accumulated in a lake-bottom, measuring the thickness of a stack of those sediments, and noting which sedimentary units lay above (were younger than) another layer. But while you could easily get the relativeages with stratigraphy, you couldn’t get good absolute ages – there were too many variables, like water levels, wind influences, and changing sedimentation rates.

It’s not hard to get the radioactive decay rates of anything if you have something like a Geiger counter: a certain number of atoms are “popping” every minute, and you could measure how many atoms were in the sample to begin with using some relatively straight-forward chemistry.

Once you have decay rates, age dating - in principle at least - is pretty straightforward.  A mineral solidifies out of a magma mush somewhere with uranium in it. By early in the 20th Century, the decay-process of uranium was well known… there were intermediate “daughter products” with different half-lives, but they all ended up at stable lead, where the decay process ended. All you really needed to do was measure the lead-to-uranium ratio precisely, and with the rate of decay you could get a handle on how long it had been sitting there since the last melt solidified. This wouldn’t work if the rock had been metamorphosed (or “stewed and cooked” as old miners would say it) since the initial solidification. In that case, the age you got was the last re-melt. 

All is not lost, however. Some really smart people eventually worked out how to get something of a handle on even this. It required some good geology, some good chemistry, and some clever statistics… but you could at least get an idea if something had been messed with since original formation.

There were other problems, however. The half-life of uranium-235 is 704 million years. Also, the precision was not that hot when you measure micrograms of uranium and lead in a mass spectrometer - and try to divide that up into 704 million years. In the best of circumstances, you get a rather large plus-or-minus – many thousands, even hundreds of thousands of years. In many situations that didn’t matter all that much. For instance when we were trying to figure which rocks arrived before which in truly ancient southern Venezuela – then 500,000 years or 5,000,000 years one way or the other didn’t matter all that much.
If you have two volcanoes, and one erupts every 20,000 years and the other erupts every 200 years, then this precision doesn’t help you at all. Unless you know the eruption frequency, you have no easy way to know how dangerous the volcano is.

THIS is why age-dating volcanic rocks is so important. Do we pour our meager annual instrumentation budget into Mount St Helens, or into (literally) Crater Lake?

There are other radioactive decay series, of course: rubidium-strontium, carbon-14 (which we use with volcanoes if we can find some fried vegetation under a flow), and the argon series. You can’t always find uranium-hosting minerals, and you usually can’t find rubidium-hosting minerals. If you find something burned under a lava flow, it can’t be older than a few tens of thousands of years, or the 14C is already all gone. But 40Ar has a more useful half-life, and argon is also a significant constituent of the atmosphere. It can be found just about anywhere in volcanic rocks – which came from a subducted ocean floor once exposed to the atmosphere.

Rats. There is yet ANOTHER problem: all that argon in the atmosphere is also going to pollute any measurement you make. Like carbon-14, which is “made” in the upper atmosphere by cosmic rays transmuting nitrogen molecules, Argon-40 comes from atmospheric Argon-39 – which is everywhere, and seeps into just about everything. If you want real numbers – true age dates – you must find a way to get clean and unsullied samples.

Where there’s a smart person, there’s a way. Believe it or not, it comes down to something as low-tech as putting your tongue on a rock. Andy - by trial and error - found that the best rocks to date were the ones in the "platy" middle section of a solidified lava flow. The final test was to see if your tongue sticks to the sample that you hammered out. Does it stick? Chuck it and look for another sample, because it won't give you a reliable age-date.

Bottom line:
It comes down to this: if we are being shot at, it’s important to know how OFTEN we are being shot at. You can plan. You can set up many forms of disaster mitigation to keep a crisis from becoming a catastrophe. Rock-dating information is crucially necessary in order to have even half a chance of predicting the volcano’s future behavior – and roughly calculating the risk it carries. High-risk volcanoes then claim the larger share of our very limited instrumentation budget. Crater Lake (the former Mount Mazama) last erupted catastrophically over 7,000 years ago. Mount St Helens has erupted more frequently than almost all the other Cascades volcanoes combined… the last period of repose was just 24 years. So with good age-dates, we invested the lion’s share of instrumentation on this critical, very-high-risk volcano.

We were relieved that we had done so when the 2004 eruption started with just over a week’s seismic warning. We had seismic and GPS “eyes” already in place and with them we could ”see” what was going on under the volcano. With a huge experience base acquired by studying hundreds of volcanoes in the US, Kamchatka, Japan, Indonesia, and Latin America, the scientists at the Cascades Volcano Observatory could predict (sometimes to within hours) when the next eruptive pulse was coming – and on 1 October 2004 they called for the evacuation of hundreds of people from the Johnston Ridge observatory.

They could not have made that emergency call if the geologists had not already carefully mapped its past eruptive products. And the eruptive history would not have been deciphered without precision age-dating. The 2004 eruption was not nearly as violent as the one in 1980. But even if it had been, the disaster of 1980 would likely not have been repeated. By 2004 we had dates and knew what this volcano was likely to do.
~~~~~


Sunday, June 10, 2012

Snowball Earth - the Faint Young Sun Paradox


Here’s a detective story for you, and it doesn’t involve a murder.

Astronomers studying young stars like ours have realized that as a Main Sequence star evolves over time, the inner core becomes denser and the fusion rate of hydrogen to helium increases. In other words, our own Sun must have grown brighter and brighter during its first 5 billion years of existence.

Careful astrometric studies have even placed some numbers on this: the energy output of the Sun 2 billion years ago is inferred to be about 70% - 85% of what it is today. This would not be enough to warm the Earth above the freezing point of water. The Earth 2 billion years ago should have been a frozen ice-ball, like Mars today. Mars is more distant from the Sun than Earth is and correspondingly cooler.

There is a problem with this conclusion, however: it doesn’t agree with ancient evidence gleaned from geology. There are sedimentary rocks in South Africa with ripple-marks and mud-cracks. These rocks are derived from volcanic ash - and therefor easily dated at about 2 billion years old. Other rocks dated at 2.7 billion years ago show fossilized rain-drop imprints. I have personally handled ripple marks and pillow-lavas (lava that is fast-quenched in water) dated at about 1.7 billion years ago in southern Venezuela. Ancient stromatolytes - blue-green algal clumps and  mats - have been found in rocks over 3 billion years old in Australia.

The evidence is everywhere: the atmosphere may have been different, but there was liquid water on the Earth’s surface as far back as we can test.

What gives?  The arguments used to explain this so-called “Faint Young Sun Paradox” fall into three main groups:

- The young Earth may still have had a lot of residual heat left over from potential energy accumulated during the accretion process. However, the surface of the Earth would have equilibrated quickly with energy received from the Sun, and the existence of solid cratons back at least 3.4 billion years ago argues for a solid crust. Energy released from the Earth’s interior has actually ramped up with the onset of mantle convection and plate tectonics, now thought to have started about 2.5 billion years ago.

- The Earth’s atmosphere retained heat more efficiently than it does now - for instance, by containing more greenhouse gasses like carbon dioxide and methane. Sufficient nitrogen can also act as a greenhouse gas under a phenomena called nitrogen broadening. There are a few questionable gas inclusions in ancient rocks, but scientists argue over how pristine the gasses in these inclusions actually are - or if they have diffused (either into the rock or out) over time.

- The Earth’s albedo, or surface reflectance, was lower in the past. Lower surface albedo could have been due to less continental area (more dark, absorbing ocean), or perhaps by the lack of biologically induced cloud condensation nuclei. How would you ever obtain evidence for something like cloud cover 2.5 billions years ago, however?

There are other suggested explanations out there. One is the modulating effect of a stronger Solar Wind in Archean times (i.e., greater than 2.5 billion years ago). Another is that due to orbital mechanics and tidal effects, the Earth’s orbit was once closer to the Sun.

This last explanation is treated skeptically by most astronomers because of some bad science propagated in several books by Immanuel Velikovsky a generation ago. The Earth-Moon distance varies depending on where the Moon is in its orbit. Lunar laser ranging experiments show that in general the Moon is receding from the Earth at a rate just under 4 centimeters per year. This is due to tidal energy being transferred to the earth (and converted to heat) via the seas, and the deformation of the Earth’s crust along with the tides. It is a logical step to infer that the Earth’s orbit around the Sun could increase for the same reason over time.

There is a major problem with all these theories: with time, the evidence for anything becomes increasingly fragmentary, increasingly suspect. It’s like a Cold Case murder - only 2.5 billion years cold.

Scientists are clever folk, however - and they keep thinking, keep looking for other ideas. Recently some of them have gone back to the fossil imprints of ancient rain-drops onto volcanic ash, and have conducted comparison experiments to estimate the density of the Earth’s ancient atmosphere. There are many variables to deal with, however, including how big will rain drops be, and how much moisture was in the volcanic ash? Careful calibration has at least allowed scientists to put a range on the ancient Earth’s atmosphere: it was between 50% and 105% as dense as it is today. This immediately calls into question the greenhouse gas argument.

We also know from other geological evidence that the Earth’s atmosphere began to fill with freed-up oxygen around 2.5 billion years ago. Rounded pyrite grains found in ancient South African sandstones, which could not have occurred in the presence of oxygen, is one proof of this. The Great Oxygenation Event came at the expense of methane and carbon dioxide, which biological processes were already starting to sequester in the form of carbon accumulating in the bottoms of ancient swamps. 

You recently drove your car to the grocery store using gasoline - some of that sequestered carbon. That same trip thus released more of a greenhouse gas to the Earth’s atmosphere.

And so the Earth grows hotter and hotter...

~~~~~

Thursday, June 7, 2012

Rocks in Campfires

Sometimes we get extremely practical questions - so mundane that no one has ever spent time scientifically researching or studying them. Another way to put this: a million people have conducted a million unreported independent experiments. However, equally many people have opinions!

Case in point: putting wet rocks from a river in a campfire:


Q: 
Hi there!
     First let me say I was so happy to find a result when I googled "ask a geologist".  The internet continues to impress.
     A friend and I recently were talking about rocks in campfires, and the safety of it.  She was convinced that solid rocks can explode with shrapnel-like effect if overheated.  I ceded that I believe rocks may able to explode, but rocks that were solid and found in a dry area would probably be safe, and that it were more likely to simply crack than to actually provide enough force to send a fragment out at high velocity.
     So obviously when we returned I did a bit of research, and found that a lot of people talk about this, but no-one seems to have any concrete evidence.  It's all either anecdotal or stated as theory.  Most of these involve "river rocks", rocks which have been exposed to water over long periods, "soft rocks" such as sandstone or pumice, the combination of the two, or simply "rocks which have air or liquid in them".
     I don't doubt for a minute that there are circumstances where gas or liquid inside of a rock can expand and cause the rock to break.  What I question is whether or not the explosion can produce a shrapnel-like effect.  Whether or not the force can be great enough to send a piece
of the rock out at great velocity, or if it would be more likely for it to simply crack with little effect.  I did a tiny bit of research only to realize that the mechanics regarding density of rock and vapor
pressure were pretty deep. The engineer in me realizes that it relies on many variables, the distance of the pressurized water to the surface, the shape of the rock, and of course it's density and the amount of vaporizable water, and that water's coordination within the rock.
     So whaddya think?  Can rocks explode like grenades?
- Andy B.

A:

That's a classic question with thousands of anecdotal answers. I have personally seen a river rock, deposited in the middle of a roaring campfire, explode. There was a distinct bang sound (several, actually), but I don't remember any pieces flying off. Others around the campfire told me that yes, they had seen fragments fly out of other wet-rocks-in-a-fire experiments, and considered anyone putting a water-soaked rock in a hot campfire as being unusually foolish. I've seen worse: in a field camp in the deep Venezuelan jungle, I watched obreros throw half-used cans of insecticide spray into a campfire with predictable consequences.

The engineer in you has homed in on the best answer (I hesitate to use "correct" here, meaning that it has been experimentally verified, or verified from personal experience, take your pick). The problem is there are too many variables.These include how "tight" the rock is, how fractured it is, how much porosity, how much transmissivity (how interconnected the pore spaces are), how fast it heats up, and how large a volume. There are probably others.

It comes down to this: to constrain the variables, one must do thousands of experiments to get anything statistically meaningful. I suspect this experiment has been "conducted" millions of times by millions of kids around campfires, but no one ever collected and compiled the results. I can't imagine anyone other than Myth Busters having the time and resources to do an appropriate set of experiments. I would be surprised, however, if they have NOT done experiments like this.

~~~~~