Monday, April 9, 2018

Red Rocks and Green Rocks?

 Some questions begin with a profound basic misunderstanding - but people are still trying to make sense out of their world, so I am grateful that they even ASK questions.
Q: At the age of 40 I am slowly figuring out geology just because I'm curious. 
     One of the things that caught my attention in Dr. Robert M Hazen's The Story of Earth is that the mantle is green: peridotite, olivine, perovskite, etc. That surprised and delighted me, because introductions to Earth science tend to show the Earth in cross section with a lava-colored mantle and core. 
     But when lava erupts, it is usually reddish orange. What happened to change it?
     Is it interaction with water from subducting slabs of ocean floor? Is it because repeated melting has allowed some of the heavier elements to sink away instead of reaching the surface, changing magma's chemical composition? Has it oxidized, in which case the Moon's maria and other airless objects in the solar system might've been green when they were molten? Or is the lava that erupts on the surface  from some other source than the mantle? 
     Thanks for answering our questions. An answer I got from you many years ago helped start my geological journey (I asked whether there could've been continents on the other side of the planet from Pangea that had subducted; you explained that continental rock is less dense than ocean floor so it doesn't subduct. Hazen's book helped me understand WHY it's less dense.)
- Ellen B
A: Good on you for actually thinking about these sorts of things.
    SOME mantle-derived rocks are green at the surface because they have significant chlorine content. However, Kimberlites, the long tubes that reach down to 100+ km depths and bring diamonds to the surface of the Earth in places like South Africa, South America, and Arkansas, are famous for being blue in color. It just means different minerals (like chrome diopside) dominate in Kimberlites. Many other mantle-derived rocks are black or gray - and often weather to brown, hence the origin of the name for one rock-type: dunnite, after the color dun originally used to describe certain beige-colored cows. 
    These colors are all what you see at ambient temperatures that exist at the surface of the Earth. However, the deeper you go into the Earth, the higher the temperatures are - this is the geothermal gradient. It's sort of like a biscuit coming out of the oven: the outside quickly cools and chills to a crust, but bite into it too soon and the inside will burn your mouth.
    When you see a red or yellow color in magma, it's because of the TEMPERATURE. This is black-body radiation, a basic physics principle. I'm attaching a photo of me next to what we informally called the "Cookie Monster" in Hawai'i. 

    The black-gray structure is a Hornito - basically a lava splatter-cone. The glowing "mouth" is a Skylight - a hole broken into the top of a lava-tube. We have used a police speed-gun to measure the speed of the lava running past and beneath this skylight: it was moving at 40 km an hour (25 mph). The whole thing collapsed about a month after that photo was taken, by the way - not a good place to be standing.  The grimace on my face is because the air temperature where I am standing was above 60 C (140 F). That blue cloud to my right is H2S gas, which engulfed me just after the photo was taken. My gas mask was on me at the time - but not adjusted to my face - and it turned my nose and throat mucous membrane fluids into sulfuric acid.     
    Translation: my nose and throat felt like they were on fire, and I took off running to get away from the cloud. 
    The colors you see correlate with temperature: red is centered around 4,000 K and yellow is centered around 6,000 K. You may have seen the dull red in a toaster: same thing is happening.
    If you could actually "see" rocks at the 30 - 50 km depths where this lava arose from, they would be yellow or even blue-ultraviolet at deeper depths.  
    Hope this helps you "see" (understand) the different reasons for rock colors. 


Tuesday, March 13, 2018

Who Is Most Guilty?

There has been a lot of Sturm und Drang about Climate Change (previously called "Global Warming" until a US Senator threw a snowball in session to make fun of the term). There has also been a lot of blame laid: (1) for why Climate Change happening (and it really is), and (2) who is still a <stuck-in-the-myth-supporting-Mesozoic> Climate Change Denier? 

Q:To what extent is the Western World having an effect on climate change compared to the rest of the world through their Green House Gas emissions?
God Bless.
- Patric P

A: By what you call the "Western World" - I will assume you mean Europe, North America, and Australia.

Greenhouse gas emissions USED to be disproportionately large from these Developed Countries. Now there are vastly increased - and growing - emissions from the so-called "BRIC" countries (Brazil, India, China).  Coal burning in East Asia and South Asia are causing massive air-quality crises in Beijing and New Delhi as I write this. 

The short answer: we are all guilty of wanting to live a middle-class lifestyle. However, the Guilt Coefficient is shifting even as this is being written.

There is another factor inadvertently adding to everyone's "lifestyle guilt," however.

To understand this, keep in mind that methane (CH4) is a far stronger greenhouse gas, perhaps up to 47 times more effective than CO2 in storing heat. As Developing Countries vie for more animal protein in their diets, the contribution of methane from pigs - and especially cattle - has dramatically increased, and China certainly leads in this growth. Basically, this is animal flatulence, and one cow can emit enough methane to fill three file cabinets in one day. Interestingly, this correlates rather closely with the increased mixing of flu viruses caused by many different animals (ducks, chickens, pigs, cattle) being kept in close proximity with humans. This is a double consequence of our common preferred lifestyle.

There is another factor, however, that may soon come to dominate all the others:

Methane clathrates (also called methane hydrates) dwarf known hydrocarbon reserves on land. These are truly vast quantities of methane frozen in ice in the sub-seafloor below about 300 meters water depth. Any future contribution from these methane clathrates to climate change is THE big unknown here. There is a strong likelihood that rising global temperatures will suddenly lead to a tipping point, and free this trapped form of carbon into the atmosphere. Likewise, a vast methane release could also come from a thawing permafrost in and near the Arctic Circle. The result of both is potentially an explosive increase in greenhouse gases in the Earth's atmosphere. 
If you want to get ahead of the curve, do NOT buy beach-front property, and consider moving to the Canadian prairie provinces. 


Friday, February 9, 2018

Is Water Wet?

Sometimes a really obvious answer comes up unbidden to a query. In the response below I had to throttle back my Inner Scientist from wanting to strangle certain abusers of social media. Facts are NOT the same as Alternative Facts. Internet Foo-Foo is NOT truth. Much of it represents all the bad consequences of the 1st Amendment to the American Constitution - without any redeeming good.

Q: So on social media there’s been a huge debate on whether water is wet or not. I believe water is not either wet or dry. So is water wet?

- Kacie M

A: This is akin to Medieval arguments about how many angels could dance on the head of a pin. In other words, it's a pointless issue. Water is water. Wet means something has water on or in it in all versions of the English language that I am familiar with. I did a cursory look and did not see a "huge debate" on social media about water being wet or not. 

Social media should NEVER be considered a source of meaningful information, as there is no vetting, no peer review of the content you see there. People make up "Alternative Facts" and post them to social media, and if it's done with flashy visuals, some weak-minded and poorly educated people might take this stuff as fact. Don't YOU fall into that old make-up-a-fact trap. That's what humanity fought its way out of the Middle Ages to get away from. Your smart phone doesn't work because of some made-up fact about electricity.

Friday, January 12, 2018

Wellwater smells of boiled egg

Q: I am from Lesotho, In my village, there is small river with a well in that river, water from this well has smell of boiled egg in it, NB. There are no swerage or any gas plan around, this well I am told has been there before that village. I want to know the possibility of mineral dispose that can be found there
- Tsepo K

A: The smell you describe is SO2. It can occur when volcanic gases broach a water table above it, and the natural volcanic H2S gas (which smells like a burnt match) is in effect "scrubbed" by the water and converted to SO2. SO2 can also form from rotting vegetation in a swamp in some circumstances, however, your location along the East African Rift strongly suggests a volcanic origin. 

This gas does not usually imply nearby mineralization, unless you are searching for sulfur deposits. 

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.