LOCATION CHANGE

This blog has been moved to http://www.askaboutgeology.com
...where new monthly and bi-monthly entries may be found.

Can you Drill into a Supervolcano to Relieve Pressure?

As recently as February 2016 an article in a prestigious science journal (Nature) raises the question if a nuclear blast will have an effect on a volcanic eruption? I’m continually amazed at the fixation people have with nuclear devices; this “nuclear question” arose during the 2004 Mount St Helens eruption and again during the 2010 Deepwater Horizon seafloor oil blowout. This is a variant on the same theme, but at least doesn’t suggest some fallout-creating experiment. People who think a nuclear device is comparable to the energy released by a volcano just haven't seen a restless volcano up close. They are a whole lot bigger than they seem to be in the films. Mount St Helens is a relatively small volcano, yet it still took me nearly 6 hours to walk out of the center crater.

Q: So I am watching this tv show (What on Earth) that NASA scientists have found a super volcano that has a potential to explode in a relatively near future in Italy. I'm super curious about a lot of things, but I won't waste your time. Whether if it's true or not, my question(s) is(are): Would it be possible to hypothetically drill into a deep caldera to release pressure on a magma chamber? I get that the chamber is quite a ways down and it would cost a FORTUNE, but if a drill was created to do so, would it work? And (if so) would it be a plausible reason for the world to come together to survive? Thanks for your time, I know you guys are busy.

- Jon T

A: A thoughtful question. You are probably referring to Campo Flegri, a 13-km diameter nested caldera in western Italy. However, there are quite a number of much bigger supervolcanoes around the earth, including at least three "owned" by the United States: Yellowstone (mainly in Wyoming), Long Valley (California), and Veniaminof (Aleutians). 

Unless you spent time on a drill-rig, you would probably not realize that even very large ones used for hunting deep hydrocarbons (like the Deepwater Horizon rig) have limited borehole sizes, particularly at depth, where they reach a human body diameter or less. The active magma chamber at Yellowstone is at least 45 miles (70 km) across northeast-southwest (wider at depth), and lies as shallow as 4 miles (6 km). There is a reason for all the geysers and Morning Glory pools: rain and snow-fall seep downward until they reach an upper magma chamber that is estimated to contain perhaps 48,000 cubic kilometers (11,000+ cubic miles) of molten magma. *

Perhaps you can see where this is leading. A single drill-rig would not even be seen in an image that encompassed the entire caldera. Not even all the drill-rigs on earth (if they could even successfully drill down that deep) would have any noticeable effect. The scales are just so many orders of magnitude greater. Think of a fly doing push-ups on the roof of your house. You get the idea. 

There was an experiment years ago to drill through a recent, 100+ meter-thick recent crust in Kilauea Iki crater on the Big Island of Hawai'i. The drill crew kept losing drill bits to the heat, but eventually they got a hole far enough down that a camera above it would catch a red glow from incandescence at some depth below the top of that lava crust. I don’t think they penetrated into the lava. Even if we had giant drills and lots of them, getting a drill bit to a magma chamber is not really possible. And it takes a LONG time to drill even a small hole in cold rock to those shallowest depths.

* Incidentally, the reason volcanologists are not particularly worried about Yellowstone right now is that estimates of crystal content in the magma mush (from seismic data) range upwards of 95%. That means it's very hot, but verging on solid. We don’t rest on this knowledge however. Geologic history tells us that a shot of deeper mantle basalt into the base of that crystal mush can quickly remobilize and prime the whole system for another vast eruption. The last supervolcano-scale eruption was 640,000 years ago, and before that another at about 1.2 million years ago. From our experience, we would first certainly see a ramping-up series of warning signs, including inflation leading to regional ground-tilt, rock-breaking manifested in a seismic swarm with a pattern to it, and the release of unusually large amounts of volcanogenic gases such as H₂S and CO₂.

Q: Thank you so much for the information! I was extremely excited to see someone replied. I guess I didn't realize our drill rigs were so small -- and the volcanoes so freakin' huge! That's absolutely mind-blowing. I love learning these new things about geology, the planet, space, etc. Science just fascinates me. Thank you for your time!

- Jon

Please sir answer this question in 24 hours or... ASK YOUR OWN SOUL!

This is a question that I actually answered in some detail three months ago, so when it came in I thought I would just point the individual at my earlier response. However, I was struck by HOW I was asked this time. To give readers a sense of what we sometimes encounter in our email in-boxes, I share this, but I'm disguising the name and identity of the questioner. You can't make this stuff up, to paraphrase Dave Barry.

Q: Hello sir

In the defination of earthquake

Eathquake is the sudden terror or shaking of earths crust which lasts for the short time. But  in 2015 the earthquake in nepal not lasted for a short time . So why we use that sentance , " which last for the short time".But Generaly in most cases it not lasted for shot time. Sir please answer this question in 24 hrs please sir i sent this question you not answered please answer . Please tel me if you want to hep ,me  or not. I f you want to help, if you want to make a bright student please help me . aSK YOUR OWN SOUL AND HELP.

tHANKYOU

A: 

I cannot answer questions about your soul, nor about mine. This is not something you would ever address to a scientist.

Volunteer geoscientists in the US Geological Survey do not see questions that arrive during western hemisphere weekends. Please do not blame us for not instantly replying to your questions from <Asia>.

I have no idea what definition you are referencing, since you did not provide that information. The simple answer is the larger the moment magnitude (Mm) of an earthquake, the longer the coda. In other words, the greater the energy released, the longer the apparent shaking will last. In fact, you can get a rough idea of how big a regional earthquake is by timing the shaking.

Epigenetic or Syngenetic Deposits: Which is Easier to Find?

The following is a rather esoteric question – definitely not an elementary school question – but it provides a neat teaching moment or opportunity. 

Q: Between epigenetic and syngenetic deposits, which deposit would be easier to find?

- Rayon P.

A: Let's review the definitions of the two types of deposit first:

Syngenetic Deposit:

            This is a mineral deposit that was formed at the same time as its parent rock – and is always enclosed by it. There are two types of syngenetic deposits: igneous and sedimentary. Some examples of these kinds of mineral deposits include paleo-placer diamonds found in southern Venezuela. These diamonds are called “paleo-placer” diamonds because they weathered out of the ancient Tepuis, eerie platform-like mountains that are the inspiration for Aracnophobia and Avatar. There is also stratabound potash (e.g., pinkish salts found in the prairie provinces of Canada and in Central Asia, that are made of potassium, a critical element for agriculture and the “secret” of the “Green Revolution” of the past century. Other examples include the huge nickel deposits found around the huge, ancient asteroid impact crater near Sudbury, Ontario, Canada. There are many other examples, of course.

Epigenetic Deposit:

            This is a mineral deposit that formed following the development or emplacement of the enclosing or host rocks. These kinds of deposits might be found on top of the host rocks, or more commonly IN the host rocks. Some examples of these kinds of deposits include placer platinum group elements (e.g., palladium, rhodium, etc.), and Comstock-style placer gold deposits (think of what triggered the Gold Rush in 1849 in California). Another example are the huge porphyry copper deposits and sedimentary copper deposits found all over the world. Note: the latter example are secondary concentrations of copper in sedimentary rocks… the copper seeped in after the sediments were formed.

            For syngenetic deposits, especially those formed during sedimentary deposition, it makes sense that if you can find one economic outcrop of the mineral you’re looking for, then you could follow the strata it is found in to find more of that mineral of interest. 

            Epigenetic deposits, on the other hand, tend to be easier to see: by the definition above they disrupt the environment (the host rocks) that they are found in. Examples that come to mind are the low-sulfide gold-quartz deposits I found while working in the jungle in southern Venezuela. The gold there is found in thick mostly-quartz veins that fill faults and fractures in the geologic units that host them. Porphyry copper deposits on the other hand are huge things that I visited and occasionally worked in while living in the southwestern USA. These are the source of much of the wiring in your house that let you read this on a computer screen – and then walk out of the room later without stumbling in the dark.  Porphyry coppers, as they are often termed, form huge bulls-eye halos in the host rock. These haloes can usually be seen from the air, and can be detected with specialized instruments like a radiometric imaging system in an aircraft, or specialized electrical geophysical methods like induced polarization.

            In both cases, there are wide variabilities is how easy these deposits are to find, depending on the particular resource being sought. In virtually ALL cases, the “easy” deposits have already been found, and modern geoscientists must search beneath younger sediments or lava that have buried these deposits after they were formed. 

            In other words, the hard-to-find ones are what we are looking for now.

Terraforming Mars

Here's a Q&A that has nothing to do with earthly geology, but may have some instructive content for future geologists. There is usually at least SOME science in SciFi novels!

Q: What would happen to the Martian atmosphere, over the course of the next 100 years, if we could build a machine on Mars that could output the equivalent quantity and composition of greenhouse gasses as are released on earth (approximately) every year?  Thanks for your time, hopefully this has not already been answered!  

- Kyle R

A: That's a rather unique question, but it begs several critical assumptions.

According to a recent Science article, Mars lost its original atmosphere billions of years ago because the planet lost (if it ever had) its magnetic field. As a result the solar wind (high energy charged particles blasted out from the Sun) stripped most of Mars' atmosphere away. So one assumption is that the planetary magnetic field is somehow restored.

Another assumption is a bit more obvious: where would the carbon and oxygen come from? Certainly not the planet's crust, as it has been degassing for billions of years and is a depleted desert now. Hundreds of trillions of tons of material would have to be brought to Mars' surface. This is actually not as unreasonable as it may sound: comets can do (and have done) this in the past... but it would require a number of pretty large comets. A colliding planetary body from the Oort Cloud on the scale of Sedna could bring the mass as well as restart the magnetic dynamo, however. A collision like that is thought to be the reason why we still have a magnetic field here on Earth... and a Moon as big as the one we have.

A final assumption is also necessary: a weaker planetary gravity field would make it easier for gases to escape the planet. So another assumption would be that somehow the planet became much more dense. A comet impact couldn't solve this one. A collision with something like Sedna would only marginally increase the gravity field of the planet. Weak gravity -> easier for atmospheric gases to escape.

I'm not a specialist in atmospheric dynamics, so I don't want to speculate what would happen if all three of these conditions were somehow met. I suspect that Mars' currently pink sky might end up a different color, however.

Q: Thanks for the thoughtful reply Jeff, I appreciate you taking the time.  The thrust behind my question was basically to get an understanding of the scale of the terraforming humans have engineered on Earth and what the impact would be if that same process was applied to another planet of similar size.  I guess looking back I should have simply asked what the impact might be of 'magically' pumping 7,000 million metric tons of  carbon dioxide into the Martian atmosphere every year (7000 million metric tons being an approximate average volume created by human factors on Earth).  Thanks again and enjoy your weekend!

 -Kyle

A: Yes, I was fascinated by the book Dune and the movie Total Recall, but the physicist in me kept slapping me on the back of the head: There's no evidence of sequestered carbon on Mars except frozen CO2 at the poles. There is only rare (indirect) evidence of water - it's a desert world. Water being low density, it would be hard to hide it on a planet like Mars or Arrakis. THAT said, I participated in several expeditions across the Empty Quarter of Saudi Arabia. Ambient humidity there is about 2% (in an Arizona summer it is around 20%). It is so dry that you have to "snuff" a handful of water every hour all night long because your mucous membranes are on fire - and cracking from the desiccation. However, I did some geo-electrical soundings along our two routes to the Wabar Impact site and found evidence of conductors - probably above-bedrock water - in several locations at about 60 - 100 meter depths.

How To NOT Go Off-The-Wall Freakin' CRAZY...

...when a Cascadia Earthquake hits.

From personal experience, when a really big earthquake hits, it is extremely unnerving. In fact, my first earthquake was a magnitude 7.3 event in Southern California, and the serious shaking lasted not much more than 3 minutes.

However, it seemed like a lifetime to me then. If asked a week later, I probably would have said that it lasted at least a half an hour.

Look at the following diagram, taken from Wikipedia:

The P is what woke me up. It hit with a bang.
The S is what rattled and then broke the windows, and stutter-walked my bed 30 cm.
The R is what finally flipped me out of my bed and onto the floor.

It took several days for the information on this event to filter down through the scientists to the government entities, to the news media, to my parents, and then to me as a 6-yr-old child. By then we were back in our house, the power was restored, and we had water pressure again.

A Cascadia subduction earthquake might reach a moment magnitude 9+ when it next occurs. That will be at least 100 times more energy than the piddly 7.3 event that launched a sleepy 6-yr-old out of his bed in Bakersfield, California long ago. If I found a M=7.3 to be that terrifying, imagine how bad a M=9+ event will be.

There are two ways to deal with the terror:

#1. Understand immediately what is happening and what will come next.
#2. Be prepared for it. Know that you have your bases covered.

#2 is something that many people more or less do (some do OK, some do better, and some do extremely well at this):
A. Have a family plan in place. Where do we meet? What channels on the battery-powered, $40 hand-held walkie-talkies will we be using to find each other?
B. Have supplies at hand, including
    i. Food. And don't count your refrigerator contents here.
    ii. Water. A LOT more water than you might think.
    iii. A battery-or-crank-powered Radio
    iv. Batteries. Flashlights. LOTS of batteries.
    v. Blankets and sleeping bags, and/or a heat source to keep warm.
C. Start checking up on your neighbors, and offer to share your stuff with them. People you may hardly know will become life-long friends really quickly.

However, the purpose of THIS blog entry or chapter is to help you deal with #1: understand what in the world is going on, so you don't go crazy. 

Next, look at the following diagram:

This will help you to understand the TIMING difference between the several kinds of seismic waves. The P wave arrives with a bang, like someone with a large hammer just whacked one side of your house. The S wave will feel different: slewing everything back and forth, perpendicular to a line between you and the epicenter of the earthquake. The R (which stands for Raleigh, or surface) waves will feel to you like you are in a small skiff after a large boat roars past, careless of his wake. You will feel like you are rolling around, up and down, and sideways . You always end up pretty much in the same place with each complete roll. 

All these things are important clues for you. This is what you do:

FIRST: as soon as the P-wave hits, look at your watch... which we both hope includes a second hand.

Second: as soon as the S-wave hits, think about what direction is PERPENDICULAR to that sickening side-to-side motion: this gives you the important clue as to where this thing is coming from. If the slewing motion is north-south, then the earthquake epicenter is either east or (more likely in this case) west of you.

Third: as soon as the S-wave hits, look at your watch again. Subtract the P-wave arrival time in seconds from the S-wave arrival time. That difference tells you how far away the hypocenter (the actual sub-seafloor rock rupture) is from you.

Use the following diagram to convert that P-S time difference into a distance::

Fourth: KEEP TRACK OF THE TIME even after you have this number. If the event is a M=9+ event, the ground will keep shaking and heaving for a full 5 - 6 minutes. THIS will give you a sense of how bad things will be in the following several weeks. If it was just a segment of the Cascadia Subduction Fault breaking, then the time could be as little as 3 - 4 minutes. This is GOOD. If the heaving and shaking runs up to 6 minutes... well, you already have #2 above in place, right? So you are prepared.

This will help: If you live in Portland or Seattle, and the P-S time difference is 20 - 45 seconds, then the event is far enough away (or close enough, depending on your point of view) to be The Big One: A Cascadia Subduction Event. 

But YOU WILL ALREADY UNDERSTAND WHAT IS GOING ON even before the first news reports start coming in (assuming you have a flashlight close and a battery-powered radio on hand). 

AND YOU HAVE YOUR PREPARATIONS IN PLACE. 

And no, you are not crazy: you are informed and prepared.