Tuesday, December 12, 2017

Where can I find obsidian?



Q: I live in Toronto, Canada and am looking to gather 60-80 basalt obsidian rocks about the size of 2 fists together. Someone told me I should drive to Idaho and that I would be able to gather them from the farmers' fields. That's a very long trip for me... wondering if you can suggest a closer place or another kind of rock that can withstand high heat and not crumble too quickly, Someone brought us volcanic rock from Iceland and it's working beautifully!!


Thank you so much!
- Michaela O
 


A: Obsidian is a glassy, naturally-occurring volcanic rock found in places like Medicine Lake volcano in northern California, and elsewhere in the western United States where volcanic activity is ubiquitous.

Obsidian is formed when a high-silica volcanic melt (such as a rhyolite) is quenched rapidly by extrusion into water. There is not enough time for quartz crystals to form, and the result is typically a black to dark green, conchoidal, glassy rock. If you are not careful handling it, it can easily cut your fingers. 

Obsidian weathers like any other rock - slowly, but it still weathers. This process is called devitrification, and you can see it well developed already in Roman-era glass. You live in Canada, in the the middle of the Grenville craton, the oldest rocks in North America, so the chance of finding un-weathered obsidian there is very small. Anything on the east side of Canada or the US will be equally unlikely to host obsidian. Iceland is nearly 100% volcanic in origin, and there is a lot of water present in lakes and the surrounding ocean, so you will find it there. I've been to Craters of the Moon National Park in Idaho, and have never seen obsidian there. This might be because the volcanism in the Snake River Plain is in the "millions of years young" range, however it could also be that I was just never in a location where volcanic extrusions encountered ancient lakes. There are places along the Cascades volcano chain from Medicine Lake, California, to Mount Baker, Washington, where you can find occasional flows that poured out under lake water - especially at Mt. Shasta and Medicine Lake volcanoes. Many of these places are national parks, however, and it is illegal to take rocks from them. 

Obsidian has been used experimentally by some surgeons to make incisions that are cleaner and less ragged (microscopically) than can be made using steel scalpels. I'm wondering if that is why you want so many samples of such a specific size?

Hope this is at least a little helpful.  

Saturday, November 4, 2017

If Polar Ice Melts How Much Will Sea Level Rise?





Probably no single item brings the scientific-political argument over climate change more into focus than sea level rise and its consequences. Here are the facts to counter the “alternative facts” that have been floated in national political discourse. See also the earlier article (http://askageologist.blogspot.com/2013/07/climate-change-is-it-real.html) on “Climate Change – is it Real?” Curiously, only in America is the science of climate change being questioned. However, only in America (and Myanmar) do we still use feet, pounds, and gallons.



In all fairness, this is not an easy scientific problem to address. Non-linear behaviors (something changing much faster than the variable forcing it is changing), and extremely complex interlocking feedback between physics and chemistry related to Earth’s weather systems, makes any modeling truly daunting. Nevertheless, scientists have developed a number of predictive models, and they are beginning to agree ever more closely.

Q: What if all the ice caps melt how bad will it flood the nearby continents, and would it change the tides of the world? How fast would the world have to react.

- Stephen L

A: There are about 21 million cubic kilometers (5 million cubic miles) of ice on the Earth’s surface. If all of this melted, it would raise sea levels by about 65 meters (215 feet). An image compiled by National Geographic magazine (http://www.nationalgeographic.com/magazine/2013/09/rising-seas-ice-melt-new-shoreline-maps/) gives a breath-taking sense of what this would mean for humanity. Florida would disappear – Washington, DC, also. This isn’t going to happen immediately, of course. For all this ice to melt would require the average global temperature to rise from a current 14C (58F) to 27C (80F). This is not impossible, especially if carbon continues to be extracted and burned at current rates or higher. 


However, there are many issues beyond polar ice involved with sea level rise:


1. Tectonic changes

2. Thermal expansion of the oceans

3. Melting ice

4. Local weather events (e.g., hurricanes)

5. Ocean albedo change

6. Methane clathrates

7. How fast will it rise?



1. Tectonic changes are an issue because, all things being equal, sea level is an equilibrium by definition and should rise everywhere at the same rate. Nevertheless, the east coast of North America is seeing a greater sea level rise than the west coast. This is because of tectonic changes, related to mid-Atlantic sea floor spreading, that are causing steady sinking along the east coast of the United States.



2. Thermal expansion is important because if you heat water it will expand. With climate change well underway (and isotopic studies indicate that it is largely man-made), we can expect all the world's oceans to expand... and therefore rise. Water is at its most dense at 4 degrees Celsius. Freeze water and it will expand (this explains why frozen water pipes burst). Warm it above 4 degrees Celsius and it will steadily expand.



3. Antarctica is covered with ice an average of 2,100 meters (7,000 feet) thick. If all of the Antarctic ice melted, sea levels around the world would rise about 60 meters (200 feet). Arctic ice is not nearly as thick, but Greenland by itself, if all its ice melted, would increase sea level rise an additional 7 meters (20 feet).



4. Local weather events are the most immediately attention-getting, and there are at least two different aspects to this. Warmer ocean water translates into more heat energy going into a hurricane - the storms become bigger and the destructive wind velocities become stronger. The recent Atlantic hurricane Irma is a case in point: it is the largest and strongest Atlantic hurricane ever recorded since measurements were first acquired. When its eye reached the southern tip of the Florida peninsula, it's outer rain bands were already into Georgia - and that was just half of this monster. However, hurricanes push seawater before them and drag at their cores a huge low-pressure zone, and this gives rise to what is called a "storm surge." The storm surge for hurricane Katrina, which devastated New Orleans in 2005, caused over $100 Billion in damage largely because its storm-surge was an additional 5 meters (16 feet) above the normal tidal differences. Add a "king tide" (when Earth and Moon are aligned and the high tide is greatest) to a 5 meter storm surge and you have a very destructive combination. It's like a giant, slow tsunami.



5. If ice disappears from the poles and from Greenland, then the albedo of the Earth will change. Albedo is the percentage of the incident light or radiation that is reflected by a surface, and is typically used for a planet or moon. In this case, ice-covered polar regions are very strong (though not perfect) reflectors of sunlight. If the ice were to disappear, the energy absorption of the polar regions would increase dramatically. Like ocean warming, this is another contributor to the non-linear character of sea level rise: a simple increase in a certain value causes secondary effects that dramatically increase the effect disproportionately in a non-linear fashion.



6. Methane clathrates (methane hydrates, "fire ice", etc.) are methane-ice held in a suspended quasi-stable crystal state found in the world’s cold deep ocean sediments (below at least 200 meters or 600 feet depth). This methane is a product of carbon being sequestered over time by CO2 capture (decayed materials falling to the ocean floor). The amount of carbon sequestered in this form beneath the world’s oceans is between 500 and 2,500 gigatons, comparable with all known sources of hydrocarbons on land. There is evidence now that ocean temperatures as deep as 500 meters are rising. Methane, being a far stronger greenhouse gas than carbon dioxide, if released in these numbers, will cause a dramatic rise in global temperatures. This is another contributor to the non-linear character of sea level rise, and helps explain why estimating climate change consequences is so difficult.



7. How fast will sea level rise happen? That is the million-dollar question for our age. The Intergovernmental Panel on Climate Change issued a report in 1995 containing various projections of the sea level change by the year 2100. They estimated that average sea levels worldwide will rise 50 centimeters (20 inches), and their +/- range went up to 95 centimeters (over 3 feet). The rise will come in part from thermal expansion of the ocean and in part from melting glaciers and ice sheets. Fifty centimeters is no small amount – this could have an enormous, disproportionate effect on coastal cities, especially during storms like Katrina, Sandy, or Irma.  Keep in mind that this estimate is over 20 years old, and more recent sea level rise estimates vary widely but are not small. Since that 1995 report there have been gigantic ice sheet calving events in the Antarctic. The most recent (Summer of 2017) on the Ross Ice Shelf is an “iceberg” the size of Delaware, that ranges from 15 to 50 meters (up to 165 feet) high... and it will all melt as it drifts northward. 



About 80% of the human population now lives within 100 km of an ocean, and the most expensive and sought-after kinds of land are ocean-front properties.  You don't have to be a rocket scientist to realize that ocean-front property investment might not be a good idea. Miami "dodged the bullet" from hurricane Irma in September 2017, but it's just a matter of time before a larger, even more destructive hurricane will hit it dead center. The loss of life and property to just Miami alone are unimaginable. The entire eastern United States is at risk, and hurricane Sandy (2012) made it clear that low-lying cities like Washington DC and New York are at terrible risk due to climate change. Giant typhoons in the subtropical Pacific are causing huge damage every year to east and southeast Asia. 

We should be have been reacting to these scenarios long ago. Places like The Netherlands and the City of Venice have certainly been taking steps to mitigate the consequences of sea level rise for decades now. However, the world needs to address the reason for it. Choosing myth over climate science is not the way to go. That approach didn't work for Big Tobacco, either.
~~~~~

Friday, October 6, 2017

Being a Volcanologist


I especially love responding to school children. This is one example.

https://mail.google.com/mail/u/0/images/cleardot.gif

Q: My name is Kasey and I am in year 9 studying Science in NSW, Australia. I am doing a group project at school on volcanologists. I have come across your work and I am very interested. I was wondering if you could answer some questions for our project. These questions include: What got you interested in volcanology in the first place?  What being a volcanologist includes? What studying volcanology includes? And any extra information you could share would be greatly appreciated.
- Kasey B

A: I'm actually a research geophysicist; I have studied and published papers and books in a wide range of topics. I got into volcanology rather late in my career.

I got into volcanology, in fact, because I had an extensive background in a lot of scientific management - leading science teams as large as 850 people in a system that the US Geological Survey calls "rotational management." I would be a manager for 3 - 4 years and then rotate back to being a scientist (which is a lot more exciting and interesting). The idea is that you can't really lead scientists if you don't understand what being a scientist actually is. So I was invited to apply for the job of Chief Scientist for Volcano Hazards, and was selected over several competitors. This allowed me to move from the "Right Coast" to the "Left Coast" of the United States, into the beautiful Pacific Northwest. It also placed me ~4,000 km closer to a daughter and two grandsons who live in Sydney, not far from you. 

Being a volcanologist means you get to work in exciting, wild places and terrains. It also entails certain risks; most of the people here in the Cascades Volcano Observatory have known at least one person who was killed by a volcano. The compensation is that we get to work on geology that is not dead... but is often (episodically) very alive and (often dangerously) active. 

You can't predict an earthquake, but you CAN predict a volcanic eruption under certain conditions. Those conditions include (1) having thoroughly mapped the previous deposits around the volcano. This means getting reliable age-dates for each deposit, something that is technically very complex and difficult. It also means (2) having enough instruments on the volcano. A remote volcano in the Aleutians can erupt, and it is difficult for us to know what is going on if the nearest seismometer or telemetered GPS system is 100 km away. An ash cloud can loft to 20 kilometers and damage or even kill an airliner flying through it along the Great Circle route from North America to Asia. 25,000 passengers a day pass through this region, so this is a non-trivial safety issue. 

Thus, volcanologists can also legitimately feel that they are protecting their fellow citizens.  I have repeatedly watched men and women take calculated personal risks to gather the information necessary - because they felt it was their civic duty. It is an honor to work alongside people so sharply focused on their responsibilities while being ferociously self-demanding, working and thinking at the highest level of exacting standards. 
~~~~~