One world, one map... OneGeology is here

Last year at GSA, I saw one of the most evangelical presentations I've ever seen about technology. (I realize that I've never been to Macworld or a Linux conference, but hang with me here.) Ian Jackson of the British Geological Survey talked about bringing geologic maps to the web, through a project called OneGeology. The goal was to create an online geologic map of the world, at a scale of 1:1 million. It's a more difficult job than it might seem - geologic maps can be considered classified information, because they provide information about a country's natural resources. And on a more petty level, geologists working across borders have a tendency to give the same rock different formal names, which makes compiling simplified regional maps difficult. (The boundary between Vermont and New Hampshire isn't exactly along a fault, but it sure seems like it is from the names and interpreted ages of the units.)

Last year, they were still in the process of getting countries to participate.

And now, the map is live. The web site says it will be officially launched next week, on August 6, at the International Geological Congress in Oslo, Norway. But some maps are already available.

For instance, here's the 1:1.5 million geologic map of Europe, zoomed in on the Alps:


On the map of Afghanistan, I can choose an "information" (well, metadata) tool, click on a unit, and read its description.

This is so cool. When I was in college, one of my favorite jobs as a departmental assistant was filing the maps. It was like taking little trips all over the world. As a teacher, I'm constantly waving my arms about some place that the students have never been, without the aid of a map. (Not effective pedagogy, though perhaps good practice for playing charades.) And worse, sometimes students ask questions about places I know only the broadest tectonic information about. (Afghanistan, for instance, or Iraq. Some of my students have been there. I haven't.) And now I'll be able to pull up a web page and show them the maps, and we will be able to try to figure out what's going on together.

This is so cool. (I wonder if this is what it felt like when Bruce Heezen and Marie Tharp first published their beautiful painting of the topography of the ocean floor?)

High-pressure metamorphism before 1.7 billion years ago?

The further back in time we look, the more difficult it is to figure out how plates have moved, or whether plate tectonics was even active. The ocean basins give us less than 200 million years of history, and in long-lived continental crust, younger events can wipe out the record of older events.

And some types of evidence are quite fragile. For instance, when oceanic crust is subducted into the mantle, it moves more quickly than heat can flow into it, and is metamorphosed into distinctive rocks that form only at unusually low temperatures for their depths. These rocks, blueschists and eclogites, are convincing evidence for an old subduction zone... but they rarely survive their return trip to the surface. It doesn't make much heating to replace the unusual minerals of a blueschist with more common lower-pressure minerals.

In the 1980's, when I first learned about blueschists, there weren't any known that formed in Precambrian time. Did that mean that plate tectonics was a new phenomenon, or that the subduction-related rocks just hadn't survived more than 500 million years? In the years since then, older high-pressure rocks have been found, but they're still very, very rare. Precambrian geology is interpreted in terms of plate tectonics, for the most part, but the blueschists and eclogites aren't part of the evidence in most mountain belts.

That's been true of North America. My corner of North America is thought to have formed from collisions between lots of volcanic arcs, from around 1.8 to 1.6 billion years ago. The evidence comes mostly from metamorphosed volcanic rocks, and from Precambrian deformation. The arcs are here, but their subduction complexes are gone.

Or, at least, their subduction complexes are mostly gone.

At the Rocky Mountain/Cordilleran section Geological Society of America meeting that I was at last week, Nina Fitzgerald and Mark Colberg of Southern Utah University showed evidence of retrograded eclogites from southwestern Utah. The rocks weren't pristine, by any means, but the authors had good evidence that the rocks had been at much higher pressures. (Not extremely high pressures - the pyroxenes didn't contain as much sodium as they do in, say, the Franciscan eclogites from north of San Francisco. And they didn't find coesite or diamonds, like in the ultra-high-pressure rocks of Norway or China or the Alps.) But they were the best candidates for subduction-zone rocks I've seen described in the Precambrian of the American Southwest. And they're the oldest high-pressure rocks I've heard of (though I've been out of the HP loop for a while now).

And they were found by people at a school with no grad students, doing good field mapping and looking at thin sections.

Ref: Fitzgerald, N.E., and Colberg, M.R., 2008, Evidence for Paleoproterozoic high-pressure metamorphism and decompression melting in the Mojave-Yavapai suture zone, Beaver Dam Mountains, Utah: Geological Society of America Abstracts with Programs, v. 40, n. 1, p. 64.

Continuous GPS monitoring: do you know where you're going?

Honestly, I meant to answer Silver Fox's question about GPS monitoring of deformation across the Basin & Range.* But I got distracted by another commenter, who pointed me to the EarthScope GPS site.

Some background: this isn't the handheld GPS unit that you can use while hiking, and which is good for locating an outcrop (or, in my case, my Subaru). These are high-precision units, and they measure changes in location well enough to monitor plate motions. That alone impresses me - it's confirmation of a theory that we accepted based on very indirect evidence. But GPS can do more - it can measure the quiet deformation that follows a major earthquake**, or swelling of a volcano that's about to erupt, or the deformation that occurs within a continent. That means that it (along with other techniques for measuring active deformation) has the potential to test ideas about the behavior of plates, on their boundaries and within their not-always-rigid interiors.

There's a big geophysics experiment going on right now in North America: the EarthScope program. Among other things, it has set up an array of continuous GPS receivers across the US.

And you can look at the results on Google Earth. (Click on images to see a larger version.)



Each red arrow represents the velocity of an individual GPS station. The longer the arrow, the faster it's moving. The Bay Area, for instance, is moving northwest at about 50 mm/year. Sacramento, on the other hand, is moving more slowly, and more toward the west.

But it gets better. You can also look at the 3D velocities:



Red Mountain Pass, not too far north of me, appears to be sinking, as well as moving toward the west. Not very fast - maybe 5 mm/year, with an error of about half that. (There are error ellipses that you can turn off and on in Google Earth.)

Mt. St. Helens is also dropping (as one might expect, given that the magma's coming out right now):



It looks like Mt. St. Helens is spreading a little, too - the north side is moving north, and the south side is moving south.

And yes, to go back to the previous question, there is a GPS station just south of Wells, Nevada.



Wells is moving west and a little up. The adjacent sites had very similar motion.

Now, this doesn't show changes in rate before and after the earthquake. That, presumably, would require more analysis of the data. And then it would take modeling to figure out whether the fault behaved as one might expect for a normal fault in eastern Nevada.

So no great insights about the Wells earthquake. But I know where I'm going now.

(The .kmz files are available from UNAVCO, if you are interested in exploring for yourself.)

*Thatcher et al., 1999, Science, DOI: 10.1126/science.283.5408.1714.

**Subarya et al., 2006, Nature, doi:10.1038.

Ice crystals on the snow

It was cold last week. Colder than I remember since moving to Colorado. Below zero (F) cold. Kinda wimpy for Vermont or Minnesota, but I'm here on a south-facing slope, with 300 sunny days a year, and it doesn't have to get to 20 below for me to feel it.



The cold, clear weather came on top of a couple feet of snow. And that has meant surface hoar.



I'm not a snow scientist. I'm not a backcountry skier, either, for that matter. My students could tell you much more about surface hoar and what it means for avalanche danger next time it snows.

Me, I just know that the surface of the snow sparkles, and that there are these tiny little tree-like crystals sticking up everywhere, and they are beautiful.



(The surface hoar photos are mine; the moon photo was taken by my husband.)

On a related note, I caught the beginning of this story on NPR about snowflakes. (I wanted to listen to the entire thing, but I have a four-year-old, and he wanted to discuss urinating polar bears. Some people hear stories about polar bears and think "oh, no, climate change!" My four-year-old thinks of the time his grandparents saw polar bears peeing at the zoo.) There are some beautiful photos linked from the story.

Teeny-tiny partial melt

I just got back from a two-day microprobe marathon - two days on what's essentially a scanning electron microscope that can do chemical analyses of very small crystals.

Here's one of our images:



It captures the coldest melt that occurs in metamorphic rocks: the partial melting of muscovite. Muscovite is the glittery, flaky mineral used for things like making eye shadow sparkle. It's very common in metamorphosed shales, but it gradually gets used up in metamorphic reactions as temperature goes up, until finally it reacts with quartz to grow sillimanite (the tiny fibers in the image) and potassium feldspar. And it can also melt, a little.

And this one did.

There's a tiny bleb that looks like a pair of sunglasses in the middle of the grain. Maybe if I outline it you'll see it:



Most of the bleb is made up of quartz (qtz). But the tiny bright spot in the middle is potassium feldspar (kfs) - exactly what you should see if the muscovite (mu) melted a little bit, and then the melt crystallized without ever escaping.

1.4 billion years ago, this rock melted. A little. (There were also a few little dikes in the field, but because we were in a contact aureole, we weren't sure if they were in situ partial melts, or if they were part of the granite. Now I suspect they were in situ melts.)

Rainbow... from above

While I was driving to work, the weather radio said the temperature was 36° F... and the dew point was 34. Huh, I thought. I wonder if it will be cloudy in town.

I could see the hills to the west as I pulled onto campus, and then the clouds started forming in front of them.

And then I saw this.



It started raining right after I finished taking a panorama of the entire double rainbow.

It cleared up in the afternoon. There's a fair amount of snow in the high country, above 10,000 feet or so. I didn't get outside to take another picture, though.

In which I go hiking with the kid and see cool minerals... like ice

There’s a lot to be said for hiking with a four-year-old. Not in terms of aerobic conditioning, and not when the goal is to scout a new field area. And, yeah, it’s important to have the right food as a bribe, and to stop frequently. But fresh air, beautiful scenery, and family time... it’s hard to argue with that. Especially with scenery like this available on a mile-long hike.

Spud Lake is about a mile up a gentle trail, up in the aspens around 9700 feet. It’s high enough that there was frost on the ground today, even at mid-morning, and the high peaks surrounding it were dusted with snow. The trail was a bit muddy, though, so it was pretty slow going. We stopped to pick up a stick that looked like the letter “J,” and to scramble around on rocks, and to look at quartz veins.

My son was fascinated with the quartz, so I pointed out that the ice made crystals, too. We picked up a frost-blackened aspen leaf so he could see the crystals on its sides, and discovered that the entire bottom was covered with them. While he was looking at the leaves with a magnifying glass, another family walked by, and the boy said: “Have you seen THIS?”

He pointed to something that looked like white hairs on an over-excited yeti. Fibrous ice crystals, holding up pebbles and leaves and bits of frozen dirt. Every shadowed spot was covered with them, when we stopped and looked. On the hillsides, on the trail... everywhere.

They looked, actually, like vein fillings – fibrous vein fillings. Perhaps I shouldn’t be surprised – ice is, after all, a mineral, if one that melts readily under earth’s surface conditions. And like fibrous veins, I think I could figure out a deformational history from some of them.

A lot of the fibers were vertical – they came straight out of the ground, like hairs standing on end. But some of them were curved – sometimes all the way over, so that their pebble or dirt dangled from a curl. I have no idea how these form, but I’ll make a guess: the pebble or dirt is particularly cold, and the ice first nucleates on its bottom side. The crystal grows down, getting water from soil moisture. And sometimes, the pebble or dirt is heavy enough that the crystal bends under its weight. The crystal keeps growing straight up from the bottom, but the top becomes curved.

There were probably ways to test those ideas... but the four-year-old started getting impatient.

He smashed the ice in a few puddles, and then we headed up the trail.

spectacular volcanic eruption photo

An amazing photo of the volcano Tungurahua (in Ecuador) was posted as today's Astronomy Picture of the Day. (I'm going to link rather than posting the picture; the picture is copyrighted.) You can see lava flows pouring down in all directions, and a blast of dark tephra blowing off to the side. You can see the prevailing wind direction on the photo, too: the wispy clouds (almost lenticular?) are typical of clouds on the windward side of a peak, and there is a little snow on the windward side, as well.

The photo was taken by Patrick Taschler, who has other really beautiful photos of the eruption animated on the front page of his site.

gorgeous picture of cross-bedding on Mars

Today's astronomy picture of the day is a view of the rim of Victoria Crater, taken by the Opportunity rover as it descends into the crater. And I could swear that I'm looking at one of the big eolian sandstones from the Colorado Plateau. Moab on Mars?

I guess it isn't a major finding, seeing evidence for wind-blown sediment on Mars. But it's amazing to see sedimentary structures from another planet. And eolian sandstones are beautiful.

field notes of the day

I've spent the last several days camping and doing field work. The weather's been wild - first it was hot, and the streams ran high with the snowmelt; then a cold front blasted through, blowing over trees with gusts as high as 60 mph; then it was lovely again; then it rained again. This might be normal in, say, New England, but June is typically our driest month (though rivers usually are high, and snow lingers near treeline).

Tuesday morning's weather was cold and damp, with drizzle off and on. I was up nearly an hour and a half before my field partners, but I didn't have the heart to shake their tent, what with the rain and all. So I made some oatmeal and then watched the birds while I sipped coffee. We were only about a thousand feet higher than my house, but up in the Ponderosa/Douglas fir forests, the birds are quite a bit different. For instance, there are Steller's jays up in the tall trees, but not in the scrubby forest where I live.

One bird that seems to be everywhere, though, is the broad-tailed hummingbird. I grew up with hummingbirds back East, but they were hard to notice - so fast, and so little, and so quiet. But the broad-tailed hummingbirds make this loud buzzing noise when they fly - it sounds almost like an insect, or like high-voltage power lines, or like somebody running a blender in the distance. So these birds, I notice. For some reason they fly up at the elevation of the Ponderosa branches, rather than down where all the small flowers are blooming. Maybe their nests are up there. But they still pause and hover at each branch for a moment, as if they expect the pines to suddenly burst into flower.

So I was watching the hummingbirds hum, when suddenly, one appeared about six inches in front of my face. I looked at him. He looked at me. He hovered for a moment, eyeing my red coffee mug, then zipped away.

I guess he was a coffee purist, and was horrified that I add hot chocolate to mine.

Or maybe it's just that a bird whose wings beat 50 times in a second doesn't really need caffeine.

The Sound of Mylonites

NPR has had this series, off and on, in which listeners record interesting sounds and then explain them on the air. I didn't have a recording device with me last weekend, but I literally stumbled across some of the most musical rocks I have ever heard: the Snake Range décollement.

I had never been to the Snake Range before, although it loomed much larger than its true elevation over my grad school career. The Snake Range is in easternmost Nevada, nearly on the Utah border, and is home to Great Basin National Park. And it's crossed by US 50, the "loneliest road," the road that continues west across the Basin and Range after I-70 ends. And in the 80's and early 90's, it was a case study for controversies over how continental crust stretches. It's a metamorphic core complex, a range with a core of metamorphic rocks overlain by a veneer of faulted and thinned sedimentary rocks. The boundary between the metamorphic and sedimentary rocks has been called a thrust fault, a low-angle normal fault, and an exhumed ductile-brittle transition. The metamorphic rocks are only around one-fifth their original thickness - pebbles stretched to pencils, thick beds of quartzite turned into mylonitic flagstone that is quarried into lovely slabs, thin and strong, with streaks of silver muscovite shimmering on their surfaces.

I was scouting out the area for a class field trip. I'm teaching Advanced Structural Geology for the first time, and I wanted to take students to see some classic fault and shear zone rocks. The Snake Range décollement is an amazing example of a mylonite, a rock in which the minerals have been shrunk and strung out by deformation within the crystal lattices themselves. Hard to explain to students the first time, and darn hard to identify in the field, and important to be able to recognize and interpret. And very, very cool.

The rocks were everything I had hoped. Perfectly exposed, with beautiful structures. Easy to find, easy to look at. I climbed to the ridgeline, enjoyed the view, and then headed down.

And then I heard something I hadn't expected. Not the rattle of a snake -- they don't call it the Snake Range for nothing! -- but a musical sound from below my feet. The thin slabs of quartzite knocked against one another, and each differently sized rock rang with a different tone. It was too resonant to remind me of wind chimes. It sounded, for all the world, as if I were dancing across a xylophone.

I wish I could have recorded it. I was sliding down the ductile-brittle transition. And it was singing to me.

It was delightful.

Edit: If you want to visit this site, it is described in at least two field trip guides:

Miller, E.L., Gans, P.B., and Lee, J., 1987, The Snake Range decollement, eastern Nevada, in Hill, Mason L., ed., Cordilleran section of the Geological Society of America Centennial Field Guide, p. 77-82.

and in more detail here:

Gans, P.B., and Miller, E.L., 1983, Field trip 6; Style of mid-Tertiary extension in east-central Nevada, in Gurgel, Klaus D., Geologic excursions in the Overthrust Belt and metamorphic core complexes of the Intermountain region; Guidebook, Part I: Special Studies - Utah Geological and Mineral Survey, v.59, p.107-16.