small earthquake swarm just north of Death Valley and Scotty's Castle

This in an interesting swarm of earthquakes just to the north of Scotty's Castle in Death Valley.

http://earthquake.usgs.gov/earthquakes/recenteqscanv/FaultMaps/117-37.html

Eyjafjallajökull eruption

I was just reading about the Eyjafjallajökull eruption yesterday and the rather bold tourist enterprise sprung up to visit it, when I see it has erupted in an explosive manner. The new path to the surface for the magma opened under the ice sheet (jokull) instead of bare ground, and water/magma interactions produce copious amounts of gas. Gas is a bad thing when it comes to magma. It makes thing go boom. Instead of a lava fountain and a tourist stop in Iceland, now we have flooding as the glacier melts, and air travel restrictions as the volcano generates large plumes up into the atmosphere from the phreatic eruption. The Icelanders are concerned about the flooding and the fluorine from the ashfall. For the geology, the composition of the magma (how much silica is in it, how much gas is in it), its interaction with the surrounding rock, and how the magma changes in composition as time increases are the interesting things. For the British sitting waiting for the air to clear, realize that ash is just magma pulverized through explosive means. Blame the gas.

Here is some good information on the location and the inflation/deflation data.

Ask a volcanologist about funding

Were you wondering about the Republican response to the State of the Union speech where Gov. Jindal derided the '$140 million for something called "volcano monitoring."'? Me too. I did a double-take, and I assume most others with geoscience backgrounds did too. Regardless of your political leanings, I would assume people would want to know if a volcano erupted (say while you were in a jet plane heading to Japan) or what the risk was if there were an eruption (if you lived in a possible lahar zone, like parts of Tacoma, for instance).

Take a gander at an interview with Rick Wunderman at DCist.

Giant's Causeway on Mars

Much like the original Giant's Causeway, the universality of basalt lava exists elsewhere in the inner solar system--including Mars. Here is a very reasonable interpretation of a basalt flow on Mars.
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I still need to scan my Iceland crazy basalt cooling images.

Granite counters: the claim of radiation risk

The New York Times has a surprising article today about the radiation risks of granite counters.

Granite is an intrusive rock--slowly cooled from magma several kilometers below the surface, the rock grows large crystals from the hundred-thousand to million year cooling period. It is also chemically more "continental"; that is, more quartz, more "felsic" minerals, as opposed to the "mafic" minerals that contain much olivine and pyroxene, two minerals rich in iron and magnesium. True granite is a chemically specific intrusive, and much of what is called granite isn't, but a cousin of it. Roughly you can say to expect quartz, feldspar (of some type, there are several), and a sheet silicate like mica or biotite.

Despite the popular image of the Earth's crust riding on an ocean of molten magma, there is little liquid under our feet. While it's hot, there is enough pressure to keep things solid. Occasionally something will upset that balance and allow the rock to melt, whether by bringing hot material up to a lower pressure (like at the mid-ocean ridges) or by adding a special ingredient to make it melt (like water released by ocean sediments subducting under a continent). Melting is complicated and rarely complete, and some minerals melt at a lower temperature than others, leaving behind and chemically changing what sort of rock it is. Granite is like this. It melts at a lower temperature than basaltic materials. It often contains more water. And it brings with it certain compatible elements including uranium and thorium. This is why granites are more radioactive than most rocks. They can contain 10-20x more uranium and thorium than the solid left behind. Some of the more exotic "granites" are pegmatites--the extremely large crystal remnants of the last little bits of liquid at the end of solidification--and they contain the highest amounts of these elements.

But is this a hazard? Granites I've encountered have rates ranging from nothing to about 10x background. This isn't that much. Time spent at cruising altitude is about 40x background at 500ft. It certainly wouldn't be worth the fuss of ripping up a kitchen, unless it was proven to be the source of elevated radon levels. After reading the literature about naturally occurring radon sources, I have difficulty assigning the radon to just a small granite piece. Any soil or rock within 4 gas-diffusion-days of the basement or slab can be a source of radon for a home, and the total amount of uranium in that quantity is going to exceed the amount in the countertop (especially the part of the countertop that is within radon's half-life time of the surface). If you covered your walls in granite it might be different.

elements in glass

Ever wondered about the elemental composition of the differently colored versions of glass? Or what exactly does "crystal" glass contain that regular glass doesn't? Have a geochemist bring back last night's empties to the lab. To first order, be careful with the fancy-ware. More iron means more color. And if you need white, try some zinc oxide.

Trace elemental analysis of a big night out
P.S. Of course this is just about these particular elements, and doesn't count the bulk silicon, oxygen, sodium and such.

Geologists and risk: field-work

A coincidental occurrence today: A co-worker sent along a harrowing tale of Bill Menke, a seismologist, taking a truck down the 900ft deep caldera wall of Grimsvatn; and a discussion of some death-defying by geologists in the field. Don't miss the rockfall heading your way photos here.

I've found over the years that slopes aren't usually as impossible as they appear, and you'd be surprised at how you can climb and descend things you didn't think possible--it just takes time and effort. I did more dangerous things growing up in Boy Scouts and Explorers than in geology field courses.

And if you want some reading in which a man gets it right, nearly every time, read Bill's blog writings. Especially Cornucopians and Conservation
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Uncyclopedia entry on Geologists

http://uncyclopedia.org/wiki/Geologist

Much of this is true.

Seen via Sabine's Garden

Mt. St. Helens webcam

A wonderful service from the National Forest Service is a webcam showing Mt. St. Helens from Johnson Ridge Observatory--and now it's gone to a much higher resolution. It'll be interesting to see what sort of near-infrared performance the new NetCam XL camera has. The old camera would occasionally pick up the invisible glow of the hot dome at night.

Watch the slow growth of the reemergent lava dome in this movie from last year. (Others here).

Online Geiger counter: off

The online Geiger counter is temporarily off while I deal with power issues in my office. I've also been thinking of taking it and a GPS on a tour around campus--there are a few places with exotic granites/other intrusives (like the Henry Moore sculpture not a few hundred feet away from my very desk) that have decent Uranium/Thorium concentrations.

Description of the counter

Martian caves

There are Martian Caves--large skylights into a world we nothing of.

The Planetary Society's Blog has the article.

The Mars Reconaissance Orbiter's HiRISE imager and the Mars Odyssey's THEMIS IR imager worked together to confirm these are caves--dark during the day, cooler than sunlit surfaces during the afternoon (but still warmer than surface shadows), warmer at night. These are huge skylights--over 300ft in size, and they overhang, meaning the cave is bigger than the skylight. The caves found are all big, partially because the THEMIS imager has a resolution limit of 100m, so they couldn't use it to refine candidate holes found in the visible HiRISE data. The diameters of the caves were from 100 to 252 meters.

One of the caves, on the northeast flank of Arsia Mons:



They were all found on the slopes of Arsia Mons, the southernmost Tharsis volcano. A global view here; it's the circular blob in 5 o'clock position from the center. These caves are likely the result of lava tubes, formed when lava cools on the surface and emptying out below.

On one of the seven skylights, they saw the floor lit; this allowed them to calculate the depth of the cave at 130 meters. The lit cave is shown below.


As Cushing, Titus, Wynne, and Christensen wrote in their conference paper, these caves offer sanctuary from all sorts of radiation, both UV and cosmic rays, that exist on the surface of Mars and would be the primary limiter of life at Mars. The caves' existence is enough to spring to life the imagines of the unseeable world inside of them; we will likely never know the wonders of what they contain in our lifetimes. It is unfortunate that they are currently only known on the slope of a Tharsis volcano--high in the thin Martian atmosphere, we are limited in our ability to land a spacecraft there easily.


Images courtesy NASA/JPL/University of Arizona

Nova: Volcano under the City

An episode of Nova I watched because it was 1. in HD and 2. Geoscience related. As unfortunately usual, another earth science Nova with excessive overdramatization. Like an earlier episode about the scablands of eastern Washington, the dramatics overwhelm any science presented. The research wasn't really explained until near the end, when they finally mentioned WHY volcanologists were going after fresh lava. Let's balance the danger/people/adventure aspect with more science. That's what Nova was for, wasn't it? Scientific American Frontiers does a much better job explaining science and what scientists do. Nova always had a bit of the National Geographic travelogue in it, but it's gone way too much to that now.

"Constant observation is necessary, for when it erupts, a new name could be added to the most deadly disasters in human history....Nyiragongo!"

Cajon Pass

Have you ever driven from Las Vegas to Los Angeles? Two thirds of the way there, you are driving along I-15 in the high, dry Mojave Desert at 3,000 to 4,000 ft, and suddenly you begin a steep curving descent, reaching very high speeds, hoping to retain control of your car. The topography is tortured with impossibly steep mountains and hills running across your path, but... you look far below and see a large wash cutting a path through the mess, and that is what the freeway follows. You see that the freight trains too run through this steep canyon. If you knew a little more, you'd also know that all the infrastructure for gas and oil to Las Vegas runs through here too. A few minutes of this wild driving and then you are dumped out into a low plain; it's cooler, more humid; the coastal air is tinged with both Pacific moisture and the exhaust of 15 million cars.

The drop, the canyon you pass through, is Cajon Pass. It is a critical transportation, infrastructure, and drainage corridor. It is also entirely a creation of the San Andreas Fault.

On your left side as you head towards L.A. are the San Bernardino Mountains. On your right, and more impressive in appearance, are the San Gabriels. They, and some other ranges to the west, constitute the Transverse Ranges, a east-west set of ranges. They are really one mountain range, formed from the compression along a kink in the San Andreas slip-strike fault. The motion of the Pacific plate, normally slipping smoothly, rides hard against the North American Plate at this location, compressing the land up into an unstable, steep, untenable range.

Why there is a usuable (although steep) pass right in the middle of the mountains can't be ascribed to luck--the San Andreas Fault runs NW-SE right through the pass. You can see a diagram of this from here: http://www.laep.org/target/fragile_habitats/images/mtns_calif.gif (The link was down today but it's been up before).
Also, I've annotated a TERRA image of Southern California:



The full image showing the whole region is here:


This is a nice block diagram showing the region from the USGS.

Imagine sliding the left side of the satellite image down and to the right, and now the San Gabriels and San Bernandinos line up.

Not only does the fault create the range, it also slices the range up.

University of Chicago and Hyde Park types will be amused by the roads in the small settlement near the base of the canyon. Google Hybrid link.

Another point of interest is the strongest plume of sediment you can see in the ocean. The Cajon Pass drains through a convoluted path of washes, creeks, and dams to the sea right there. Is some of that silt from the rapidly eroding rocks of the Pass? Absolutely.

I originally started writing this entry in August, trying to start out with a broad comment about how geology completely controls topography. I am amazed at how every geographic and topographic structure can be explained geologically. That approach to the entry didn't work, so instead I wrote about a specific instance. And what's amazing is I am finding these explanations everywhere.