(image) I first ran this post in August 2009 and again in July 2011, but I think it's worth a repeat. . . During my 2006 trip through the Sierra Nevada (at Stop 12 of the Subduction Tour, to be precise), I came upon a floppy water-resistant field hat lying on a dusty slope beside the road, looking like it had been there perhaps a few months. For no particular reason I grabbed it and tossed it in the back seat. When I came home I tossed it under a table in my office. Then one day I had a cobwebby job to do and clapped it on my head. I have grown attached to this foundling hat. It's a size 7-1/2, a good fit, and it has a sunburst drawn in ballpoint ink on the front edge of the brim.
They say that anything is possible on the Web . . . did you lose this hat? You'll have to fight me for it.
The Hat -- Geology Guide photo
The American Geophysical Union is the world's largest publisher of Earth science research--and space science too. As an AGU member of long standing, I've enjoyed subscribing to AGU journals for my own information and pleasure. As a science writer, I've found AGU journals to be an endless quarry of ideas and sources. In both roles, I've often wished that the public could join me in looking at the primary literature. I've pointed out that the so-called open literature is open only to those who pay, and almost five years ago I urged publishers to at least make their classic papers open-access.
Today the AGU announced that all of its journal content will become freely available after 24 months, starting on 1 May. This will be a signal service, in particular, for climate science. The more people who can root around in the real literature, the better grounded the larger conversation will be. The AGU journals include the venerable Journal of Geophysical Research or JGR, the fast-breaking Geophysical Research Letters or GRL, the authoritative Reviews of Geophyics, and a bunch of others that are flagships of their fields. The content being opened up goes back to 1997, when everything went digital. Ideally, the AGU will put some money into digitizing the earlier catalog too.
In geology, the rocks have a way of messing with our pretty schemes. One instance I'm thinking of involves the base of the geologic time scale. The Earth itself is about 4.5 billion years old--but the time scale starts at the base of the Archean Eon with a time unit called the Eoarchean Era, running from 4.0 billion years ago (4 Ga) to 3.6 Ga. Like most of the Precambrian time periods (and unlike the more familiar Phanerozoic time periods), the Eoarchean is based on arbitrary numbers rather than notable geologic events.
When this part of the time scale was put together, we figured, from long experience, that there weren't any rocks older than 4 Ga. So much for experience: now we have rocks in hand that are older than the official time scale, and some zircon crystals that are reliably dated at 4.4 Ga. Today, Hadean time is no longer a matter of conjecture. So I hope someone is thinking about setting up signposts in deep time for the Hadean Eon. I suggest the Paleohadean for 4.5 to 4.4 Ga, the Mesohadean for 4.4 to 4.2 Ga, and the Neohadean for 4.2 to 4.0 Ga.
Here's an oddity: in the Cenozoic Era, the Paleocene Epoch comes before the Eocene, but in the Archean the Eoarchean comes before the Paleoarchean. Why is that?
Hydraulic fracturing (fracking) is the well-publicized process by which "tight" rocks can be made to produce oil and gas. It involves explosives, and in a handful out of approximately a million cases small earthquakes have resulted as existing stresses in unmapped faults were released. One of those exceedingly rare cases happened in Ohio last month, and the authorities revised the regulations today to ensure greater caution when the signs arise again.
Now, when permits are issued for drilling within 3 miles of areas of known seismicity (magnitude 2 events, which are usually barely felt), the drillers must install seismic monitors. When the monitors detect events of magnitude 1, drilling stops while the cause is investigated. Interested groups approve: the Interstate Oil and Gas Compact Commission calls it "a sensible response to a serious issue" and the Groundwater Protection Council says "these additional standards add even more strength to Ohio's already comprehensive regulatory program."
(image) Yesterday's magnitude 8.2 earthquake off the coast of northern Chile was significant to scientists because it was widely anticipated and because it filled the largest remaining "seismic gap" in a large swatch of the South American subduction zone. This map (and one like it at Cornell University) shows the rupture zones of historic earthquakes. The area of yesterday's event matched a large earthquake in 1877. We now appear to have a full set of quakes rupturing this part of the boundary between the South America and Nazca plates.
It's still not clear how much meaning there is to a "seismic gap." The gaps are a reverse way of looking at "fault segments," which are distinct sections of plate boundaries that appear to define typical earthquakes, but earthquakes aren't tidy things that always know their places. The Tohoku quake of 2011 spilled across several "segments" of the Japan subduction zone. There's no guarantee that yesterday's quake has "prevented" a giant magnitude-9 event that would encompass several of the Chilean segments. But that's for the experts to discuss, and they already are.
Other highlights of the quake worth visiting:
The hydracoustic station at Robinson Crusoe Island recorded the quake's sound
The IRIS Consortium has a "Teachable Moment" feature on the quake
Austin Elliott's Trembling Earth blog gathers a lot of good links
Deutsches GeoForschungsZentrum GFZ image
(image) One of America's unsung senior geologists, E-an Zen, died on 29 March at the age of 85. Born in China, he emigrated to the U.S. and earned a doctorate in 1955 from Harvard. A 30-year career followed at the U.S. Geological Survey, then 23 more years on the faculty of the University of Maryland. He was basically a mineralogist, but his field skills were formidable and he made large contributions to Appalachian geology, metamorphic petrology, and mapping of northern Rockies. Anyone who's looked into the literature of those fields has read his papers. He earned his full share of awards: membership in the National Academy of Sciences, the Geological Society of America's Day Medal, the Mineralogical Society of America's Roebling Medal, the Geological Society of London's Coke Medal, and more.
In 1991 Susan Werner Kieffer, no slouch herself, recalled fieldwork with Zen: "I pride myself on being fit, but when I'm in the field with E-an, I'm always so out of breath that I can't talk, and thus I'm subjected to questions. For example, I was recently subjected to 3–4 days of questions about granites, migmatites, structural geology, epidote, and eucalyptus while working with E-an at the Cooma Granite in Australia. . . . I was so out of breath and confused by the rocks we were in that I wasn't providing him any feedback. E-an could sense my frustration and, with the sensitivity so characteristic of the man, politely changed the questions: to ones about scientific ethics, education, literacy, policy, religion, or philosophy—subjects about which he is deeply concerned."
Those wider concerns marked Zen's tenure as president of the GSA in the early 1990s. In his Presidential Address of 1992, published in GSA Today, he told his audience, "Science is too important to be left to the scientists. Geology directly impinges on human welfare and so cannot be an ivory-tower science. Conservation of the environment, discovery and recovery of Earth's resources, avoidance of natural hazards, disposal of wastes, forecasting of global change, decisions on land use, equity for the future—these and other issues need geological knowledge both for technical resolution and for guiding public policy. Public policy needs public support; we ignore the public at our peril." He went on to discuss scientific literacy, ethics, education and geologists' obligation to do public outreach.
I wasn't there that day, but I recall being impressed when I read his words, and I continue to take his ideas seriously in my work here on About.com.
People might think that geologists have deeply centered awarenesses, and of course we do, but we're just as deeply concerned with appearances and surfaces. Above the bedrock roots of a landscape, a whole geosphere of young and attractive sediment gets slavish attention. This rich, thin world has three S's—soil and sand and silt—and three C's—clays and clastics and chemical precipitates. All of them are dancing their way through a gigantic cycle involving the crust, mantle, ocean and atmosphere: the whole world, basically. The three C's and S's of surficial Earth have their own article, "Minerals of the Earth's Surface," for your pleasure. Their part in the world cycle is a destructive influence that aimless youths may find attractive, particularly if they're outdoors a lot. It's called erosion, and the world couldn't operate without it.
(image) Geologists are serious about things, but surficial features are fun too. This geologic character—disgusting or fascinating, depending on where it erupts and your age—is a little mud volcano. Recreating one of these in the yard would be tempting if I had a few million to play with; like an aquarium but with mud volcanoes instead of piranhas. They're shallow acquaintances that arise from roots only a kilometer or so deep—not the impressive depths where lava arises. Mud volcanoes have their own gallery here showing their four basic types, so you too can avoid them on the dance floor.
If you think of earthquakes like alarm clocks, then lots of people, maybe most of us, respond by rousing briefly and then hitting the snooze bar. California experienced its largest earthquake in years just this month—it was a magnitude 6.8 shaker three weeks ago off the coast of Eureka, in the northernmost part of the state. It was felt all the way from Eugene to Reno to San Francisco. That made only a little news. But a quake that was a hundred times smaller, at magnitude 5.1, got the whole nation's attention because it struck a nerve center, in Los Angeles under the town of La Habra. Millions of people felt it.
The La Habra quake appears to have ruptured the same blind thrust fault responsible for the 1987 Whittier Narrows earthquake. That name probably means nothing to non-Angelenos, but the Whittier Narrows event (magnitude 5.9) got in the news for the same reason, and I'm sure a lot of locals remember it like yesterday. The quake didn't rupture any of the long, notorious faults in the San Andreas fault complex that are the main threats for a real Big One of magnitude 7-plus. Seismologically, it was a sideshow. Nevertheless, even small thrust faults like this one can raise a Big-Enough One. An all-star cast of earthquake scientists at the Southern California Seismic Network prepared a special page for the La Habra quake with lots of detail from the scientific side.
This earthquake didn't do a lot of damage, although I feel for the handful of people with ruined homes and those picking up broken and displaced things. It's a good teaching moment for the nation's second-largest urban area. Maybe some of them won't hit the snooze button ever again.
It was the afternoon of Good Friday, 27 March 1964, in most of Alaska* when an enormous earthquake ripped the plate boundary off the southern coast over an area one-third the size of California. The shaking went on for several minutes. The U.S. Geological Survey has a video about the quake that runs just over 4 minutes. Watch it and imagine yourself being shaken to a terrifying degree that whole running time. It was, and remains, the largest earthquake ever measured in North America, and second-largest in the world. The earthquake, like several others in history (1755, 1906, 2004), produced great advances in earthquake science.
The one we commemorate today happened to fall at the threshold of plate tectonics. It showed, clearly and without a doubt, that events like it were a manifestation of what was soon named subduction—parts of Earth's surface thrusting over/beneath other parts of Earth's surface. Its behavior directly accounted for folding in Alaska's rocks that occurred as the result of thousands of such quakes over millions of years.
Subduction megathrust events were a missing piece in the engine of the world, which scientists were dimly grasping at the time under the terms "continental motion," "polar wander" and "seafloor spreading." The textbooks don't give the impact of this event, and the man who first documented it—George Plafker of the USGS—sufficient credit. It was merely a descriptive achievement, after all, not a grand synthesis or brilliant insight. Plafker's 1965 paper in Science the following year (find it here) was the fruit of exhaustive fieldwork, done without satellite images or lidar or even computers, just pens on paper. Yet everything that followed used what he learned. More details here.
*Alaska was under several time zones in 1964. Mainland Alaska was on Alaska time, the Panhandle was on Yukon time (only in the town of Yakutat) and Pacific time, and the Aleutian Islands were on Hawaii time. The earthquake is officially dated as March 28 because it was 3:36 a.m. the next day in Universal time.
2014-03-25T13:54:53ZThe large, deadly landslide that struck near the town of Oso, Washington on March 22 was a slow-motion tragedy. The first few days were the worst part of it—emergency responders were working without rest to find survivors, yet much of the ground was too dangerous to step on. The anxiety and frustration must have been terrible. So I grant slack to the weary manager of the county's emergency management department, who told the press, "The area was mitigated very heavily. It was considered very safe. This was a completely unforeseen slide. This came out of nowhere." Many people who don't know geology think that way. To geologists, what he said was mostly incorrect. This is an area of large, well-mapped landslides. Washington geologist Dan McShane writes a blog, Reading the Washington Landscape, where he's been pulling up background information on the slide and its neighborhood. (I've had it in my Washington Geology resource list for some time.) The landscape has landslides written all over it. As McShane put it on the day of the slide, "Landslide wonks knew exactly where this slide was as soon as it made the news." Later he posted lidar maps of the area, showing the landscape with all trees and buildings removed. Take a look. Outlines in red, made by McShane from county data, show some of the landslide areas. The area of last weekend's slide is the one on the right. That is to say, the latest slide was in the scar of an older one. In fact, the lower part of that older slide moved again in 2006, pushing the river southward. The area of the 2006 slide is the part that was "mitigated very heavily," meaning that the ground was drained and wreckage cleared up. Such steps can stabilize small landslide deposits, but they can't stop unstable mountainsides from collapsing over and over. I have no doubt that the geotechnical engineers and geologists who dealt with that 2006 slide knew the overall situation perfectly well. But scientists, for better or worse, aren't in charge of things, and people determined to do what they want can't easily be made to understand the risks they're taking. Until the ideal world arrives, people need to learn on their own. The technology that could help is easily envisioned. Sprinkle a bunch of RFID chips (or even just distinctive reflectors) on hillsides like this and map them regularly with GPS and lidar. The premonitory signs of landslides like this can be detected and warnings can be issued with good data behind them. The largest non-volcanic landslide in North American history happened just last year, inside the massive open pit of a copper mine in Utah. But because the pit was closely monitored, the workers cleared out 7 hours beforehand and not a soul was injured. The technical details were published January in the open-access journal GSA Today. On the other hand, it would be cheaper just to keep housing away from danger zones. Background: About landslides and mass wasting 8 landslide types in photos The Landslide Handbook, free from the U.S. Geological Survey Annotated lidar image from Dan McShaneThe 2014 Oso, Washington Landslide: Completely Foreseeable originally appeared on About.com Geology on Tuesday, March 25th, 2014 at 13:54:53.Permalink | Comment | Email this[...]