Thursday, February 16, 2012


Probably the hottest geologic topic right now is called "fracking", which is short for "hydrofracking", which is short for using water (hydro) pumped down wells at enormously high pressures to fracture (frack) so-called gas-rich "tight" rocks. The idea is that a huge formation found all over the north central and northeastern US, called the Marcellus Shale, is... well, shale. Shale is a rock formed from deeply rich, usually black muds at the bottom of swamps. These muds are loaded with carbon, because they are mostly organic in composition (e.g., "stinking swamp muck"), and carbon usually "matures" under heat and compression to a number of different forms ranging from coal through liquid hydrocarbons to different forms of carbon-based gas. A major component in the Marcellus is methane, a.k.a. natural gas. But shale itself looks typically like a dark gray to black, raggedy-edged yard stepping stone. It's just a gassy version of stepping stone.

This particular shale formation is widespread, extending from New York state (whose town of Marcellus is the type-locality) throughout much of Appalachia. It is OLD: around 400 million years old (Devonian age). It is also "tight", which oil drillers coined to refer to a rock that didn't let gas or fluid pass through it very easily. However, if you can break up the formation - fill it with fractures - then just the pressure of the overlying rock could potentially force trillions of cubic feet (the standard measurement of natural gas) out of your well. And guess what? The Marcellus is located strategically close to where it would be needed most: the northeastern US.

Fracking, however, means more than just water being injected. It also involves proprietary (e.g., secret) mixes  of solvents and lubricants and sand. Yes sand: after the hydraulic pressure is released, the particles of sand will keep those new fractures open so the natural gas trapped in the shale can get out. And the lubricants and solvents are designed to keep the fluids flowing - keep everything slick, not gooey. The theory, of course is that the top kilometer or so of the frack well is cased (lined with steel tubing) and that tubing is cemented into the hole to stop any potential leaks. This in most cases will extend beyond the groundwater being used by overlying communities and keep the fracking fluids and your drinking water separate.

The idea is that the solvents will sort of, you know, be nice, stay where you put them, and behave themselves. Here's a clue for you to think about however: the secret nature of those mixes. Why keep those chemicals secret unless you are trying to hide something? Another thing to think about: no underground system is "closed" - sealed off for eternity from everything else around it. Groundwater specialists know that there is always movement of groundwater through the sands and rock that it saturates. That movement can be as low as a few tens of centimeters per year, but is often far higher than that. So anything underground is not going to stay where it is - unless it's solid. Maybe you can see where this might lead to by now. There are whole communities in Appalachia, Colorado, South Carolina... and for that matter all over the world where the groundwater is poisoned for one reason or another. It could be mine waste leaching into the ground in West Virginia or Colorado. It could be a leaky tank beneath a service station in Illinois. It could be an abandoned landfill from a World War II Army base in Arkansas. It could be a plutonium-loaded and corroding tank on the Hanford nuclear facility near Pasco, Washington... leaking into the adjacent Columbia River that runs through Portland, Oregon. I kayak in that river, so it gets personal.

And "stuff" always moves.

I'm in the middle of a PhD in economics right now at University of _, and right now I'm working on possible dissertation projects. One project I've been thinking about is looking at gas drilling (specifically fracking), and looking at the economics of drilling. For example, I'm thinking of looking at the economic impact of drilling in the Marcellus Shale formation in Pennsylvania, where there's been a recent expansion of fracking.
I have a geological question for you that I haven't been able to figure out. Is there a way to determine a map that gives both (1) the depth of the top of the Marcellus formation and the (2) depth of the bottom of the Marcellus formation? When I look at standard geological maps, there doesn't seem to be a way to convey that information well in a 2D map, since the information I'm trying to figure out is 3D. I don't know how well this information is known. I imagine that mapping it would be tough, since it is expensive to take deep-earth samples.
Eric L.

You have certainly picked a relevant (and highly politicized) subject - and one that will remain relevant for many, many years. Look forward to full employment for a long time! What you are searching for is an Isopach map - a map contouring the thickness of a particular sedimentary unit - of the Marcellus Shale. You can be absolutely certain that the Oil & Gas companies have these. These are what they base their drillstring-whipping efforts on: where to guide the drill (first downwards, then they "whip" it horizontally to follow a particular stratigraphic horizon). It's a 100% bet that if they DIDN'T have this information, their efforts would be a hugely expensive bust: it's not economic if a million-dollar drill-stem can't be contained within the producing horizon. The stratigraphic unit of interest can be quite thin, but spread over a large area - that's where the dollar value starts clocking in. The strata are almost never horizontal and rarely stay at the same depth over any significant distance, either, so you need to know where the top is and where the bottom is.

This inherently 3D information is generally obtained using 3D reflection seismic surveys... very expensive, but current technology has the capability of resolving layers as little as 5 meters thick when buried more than 2,000 meters down. It's really amazing where brains and (nearly) unlimited resources can bring technology these days.

One reason that this is not found much in modern geologic maps is that the graphic systems used to display and evaluate the unit(s) of interest are also 3D - the top and bottom of the Marcellus is inherently three dimensional so must be viewed that way to be meaningful. The display technology is handled using workstations costing $20,000 or more, with software that is far more costly still. Generally the people working with these data - and planning the drilling programs - are using 3D glasses and working off of multiple 50" plasma screens.

The problem facing YOU (and also the US Geological Survey) is that this information is highly proprietary: one oil company has very strong incentives to keep the information secret from competitors... AND from government entities that might want to tax and/or regulate them. I know some people in the Energy Program of the USGS these days... but their programs are more oriented towards doing large-scale resource estimates. THESE things are available in the public domain: If you want more detailed information on the Marcellus Shale, my first recommendation is to get in touch with one of the "Minors" - smaller Oil & Gas companies working the Marcellus right now - and see if you can meet with one of their geologists. Explain what you are trying to do, and see if they might be willing to talk with you and share some of their data (perhaps even show their 3D data to you, after you sign a non-disclosure agreement).


Saturday, February 11, 2012

A Desert vs a Tundra

Like all science fields, there have been arguments on what a particular word really means. In the example below, the question comes up: what is a desert? Would the Antarctic qualify? Does it have to be hot and sandy?


I'm having an argument with a friend;
What is the largest desert? The Sahara or Antarctica?
Can Antarctica be considered a desert or a tundra?
What is the difference between a desert and a tundra?
Thank You,
Ashlee C.


Hi, Ashlee,
Here's the definition of a Desert :
1. a region so arid because of little rainfall that it supports only sparse and widely spaced vegetation or no vegetation at all: The Sahara is a vast sandy desert.
2. any area in which few forms of life can exist because of lack of water, permanent frost, or absence of soil.
3. an area of the ocean in which it is believed no marine life exists.
4. (formerly) any unsettled area between the Mississippi and the Rocky Mountains thought to be unsuitable for human habitation.
5. any place lacking in something: The town was a cultural desert.

Here's the definition of a Tundra:
one of the vast, nearly level, treeless plains of the arctic regions of Europe, Asia, and North America.

Some Additional Information:
The Sahara covers about 8.6 million square kilometers; I have spent time there and it is pretty huge, but not a contiguous sand-dune desert like the smaller Empty Quarter in the Arabian Peninsula. You can at least drive across the Sahara and have a chance of getting to the other side.

Antarctica covers about 20 million square kilometers - quite a bit bigger.

From the definitions above, Antarctica is a Desert, but not a Tundra. The Sahara is a Desert, but not a Tundra. Antarctica is more than twice as big as the Sahara.

I hope this settles your argument.

Friday, February 3, 2012

Volcanoes, Earthquakes, and Plate Tectonics

Yes, they ARE connected.

With two notable exceptions, volcanoes are associated with (a) tectonic plates splitting apart (Iceland and east central Africa come to mind) or (b) tectonic plates that are coming together (the Pacific Ring of Fire comes to mind). In the former case, magma is simply rising into an opening gap between crustal plates that are being pulled apart - like the mid-Atlantic Ridge. In the latter case, an over-ridden oceanic plate, loaded with water and chemical sediments, heats up as it goes deeper into an increasingly-hotter-with-depth mantle. Something called partial melting takes place: the lighter materials like silica and water and CO2 segregate from the down-going slab and float up - Mount St Helens in the Pacific Cascades, Sheveluch in Russian Kamchatka, and Mount Fuji in Japan are examples of these.

The notable exceptions are the volcanoes of the Hawai'ian Islands in the middle of the Pacific oceanic plate, and Reunion Island in the Indian Ocean. The generally accepted understanding for their existence is that a "hot spot" in the Mantle feeds up through a moving crust (the Pacific plate) and creates a string of volcanoes. In the Hawai'ian chain, the oldest are in the northwest, and the youngest are in the southeast on the Big Island. There's even a new one, called Loihi, that is forming on the ocean floor even farther southeast of the Big Island.

When we talk about moving tectonic plates, it's hard to come up with a reference point that everything is moving with respect to... Certainly the North American continent is moving westward over the Pacific and subsidiary plates, but Kamchatka is moving southeast over the same plate(s). If in fact there IS a "hot spot" in the middle of the Pacific plate - perhaps that is the one non-moving reference point on this entire planet.


With the increased recent activity around the "ring of fire", New Zealand, Japan and Gulf of California, is there an increased risk for earthquake in other areas of the ring of fire?
Thank you
David H

Geologic events never happen according to a regular clock - sometimes things are quiet around the Ring of Fire, sometimes several events happen in relatively close succession. There is no recognized relation between the huge Tohoku earthquake in Japan and the much earlier Christchurch, New Zealand event - they are too far apart in both space and time. THAT said, there have been several cases observed where a large earthquake has "lit up" distant volcanic or earthquake-prone areas.  The large Denali fault earthquake of November 2002 apparently triggered swarms of small earthquake in Yellowstone, for instance. Nothing big happened, but there were a cluster of small earthquakes that correlate closely with the p-wave of the Denali event passing through.

The likelihood of other earthquakes around the Ring of Fire correlates much more closely with the rate of subduction - how fast the continental plate is over-riding and "smothering" the oceanic plate. This rate is much higher off the coast of Kamchatka, in eastern Russia for instance (about 8 cm/year), than the collision rate of the Pacific Northwest (moving only about 2.5 cm/year). For this reason the volcanoes in Kamchatka are historically much more active than those in the Cascades. In the 10 years that I've been receiving daily volcanic notices about Kamchatka, I'm at a loss to think of a time when a volcano in Kamchatka was not erupting. Whereas in the last century, here in the Pacific Northwest, we've only had Mount Lassen erupt (1915-17), then Mount St Helens in (1980-86).

Any plate motion will translate into earthquakes - the plates are scraping past each other - and the subduction (over-riding plate) earthquakes can be real doozies.

Slower tectonics translates to a quieter life: fewer earthquakes, fewer volcanoes.


Wednesday, February 1, 2012

Nuke it!

While I was serving as the chief scientist for volcano hazards of the US Geological Survey, Mount St Helens chose that particular window of time during 18 years of quiescence to erupt (October 1, 2004). At the time I was also still volunteering to answer questions for Ask-a-Geologist. Perhaps because of my calling at the time, I received not one but two AAG queries that went something like this (I couldn't find them in the archives or I would quote directly):

Why can't you drop an atom bomb on <Mount St Helens> to stop it from erupting?

A variant on this suggestion is to use a nuclear device to trigger a pending eruption at a time of your choosing.

There are several problems with this approach:
A. Highly radioactive debris scattered widely over a populated area.
B. You would need to get the device under the ground to open the ground.
C. The inherent energy of most volcanoes is far larger than any nuclear devices built by man.

"A" is, I hope, obvious. Nearly as many people died of radiation poisoning after the Hiroshima uranium bomb was dropped than died of the immediate blast itself. Half-lives for things like the unstable isotopes of strontium and cesium are looooong - thousands of years - and they are poisonous the whole time they are decaying. Plutonium is, gram for gram, far more deadly than botulinum toxin.

"B" is basic physics. A small stick of dynamite will blow OPEN a standing safe by over-pressuring it, but a cluster of dynamite sticks taped to the outside and detonated may or may not crush a safe door down onto the inner contents of the safe. Despite what you may have seen on Butch Cassidy and the Sundance Kid, safes don't blow up nicely.

Translation: you will need a very big, very expensive drill to place the nuclear device at a strategic place. Assuming it was powerful enough, that is.

When you come down to the many trade-offs, it's far easier to just (1) monitor the volcano, and (2) evacuate people when it's restive behavior starts accelerating and the seismometers start going ape on you.

"C" is just a numbers game. The Hiroshima uranium bomb and the Nagasaki plutonium bomb had estimated explosive yields between 12,000 and 20,000 tons of TNT. For you metric nerds out there, a metric ton of TNT equivalent is a bit over 4 gigajoules.  Mount St Helens' 1980 eruption was a VEI = 5 level blast. That's short for Volcano Explosivity Index, and a VEI 5 is about 10 times bigger than a VEI = 4; the values are approximate, and approximately logarithmic. The 1980 eruption of Mount St Helens released the equivalent of 20 million tons of TNT. That's between 1,000 and 30,000 times more energy released than the Hiroshima atom bomb.

The eruption of Yellowstone supervolcano about 640,000 years ago has been estimated as a VEI = 8 event, or 1000 times larger than the 1980 Mount St Helens eruption. That's between 1,000,000 and 30,000,000 times the power of a Hiroshima bomb.

Translation: a nuclear device is to a VEI 5 volcanic eruption, as a fly doing push-ups is to you doing push-ups. I may be exaggerating a bit with the fly, but you get the point. Volcanoes are BIG. That's why no one has ever seriously considered engineering around a volcanic eruption. Just get out of the way if you can.

If you want to open a can of spinach, ya gots ta squeeze it, to quote Popeye. No sissy atom bombs.