The largest geologic structures on the planet - do they drive volcanic hot spots and mass extinction-level flood basalts? We don't really know, but definitely maybe.

Nordic-related miscellany:

• Dating the Eldgjá eruptions (the largest flood basalt eruptions in historic time) with methods including the Icelandic Book of Settlement and Deeds of the Saxons*
• 3,400-year-old beads in Danish graves were made by the same glassmakers used by King Tut 

 *(Inspired by this collection of aerial images of the Eldgjá flows)

Since cursory Googling has not revealed an extant one, here's a (moderately Lovecraftian) mnemonic for the Proterozoic geologic periods:

Six red obelisks stand calmly, each steeply tilted, cold, eternal.
[Siderian, Rhyacian, Orosirian, Statherian, Calymmian, Ectasian, Stenian, Tonian, Cryogenian, Ediacaran]

You're welcome!

Soviet geology: an exotic and romantic business:

Large sections of the country were still waiting to be explored and mapped. Foreign travel was still impossible for most Soviets, so idealistic youths were drawn to geology for the thrill of adventure and exploration. Some of them really thought they could find personal freedom, if not by going west, then in the distant corners of the wild east....

They mapped, carried loads of samples, fished and hunted, wrote poetry, drank vodka, and sang songs around the campfire. In fact, many Russian musicians and poets (Nobel laureate Joseph Brodsky included) started out as geologists or worked as technicians in those parties. Few outside of Russia know that it was geologists who started an important movement in modern poetry in St. Petersburg in the 1960s, called the “Geological School.” Furthermore, geologist authors dominated a genre of unofficial, often politically risqué songs (“bard songs”). The songs were about cloud shadows in the tundra, windy mountain passes, shamans and dervishes in time-forgotten villages, apatite [sic..... unless they mean the mineral], camaraderie, lack of cigarettes, and nostalgia for home and love during long field seasons.....


Even until the late 1980s, saying you were a geologist to girls in St. Petersburg was a great pick-up line — often greeted with admiring smiles and questions about exotic places and wild excesses in the field. Yet when I told my father that I was going to become a geologist he said: “Do you want to be one of those inebriated loudmouths with backpacks and guitars who bellow songs on night trains?”

Apparently, the composer Giya Kancheli (recommended) came out of such a background.
 

Holy moly! An earthquake in Pakistan just created a new island! It's a small island, but still.... Now that I'm living in a place where I can see fault scarps cutting our very small and young alluvial fans, this makes my flesh crawl a bit.

New Mexico is stretching an inch every 40 years. Surprisingly evenly, as it turns out.

Photo gallery: 2011 in Volcanic Activity

My new favorite resource: Find online versions of geologic maps (warning: huge time sink). Use the interactive map and limit your search to "Maps in NGMDB Library". Here, for instance, are all of New Mexico, all of Nevada, and Dinosaur National Monument. Smaller scale maps are available.

More research on the Gamburtsevs, the range of Alp-sized, glacier-carved mountains that lie buried beneath miles of Antarctic ice. Includes a cool fly-through animation!

New modeling indicates that the Chicxulub meteor probably did not cause the eruptions of the Deccan Traps. Still a hell of an impact, though, 2 million times an H bomb!


HT: Instapundit.

Swarm of earthquakes on a previously unknown fault in western Nevada

Yellowstone Volcanic Plume Larger than Previously Thought

New seismic fault discovered in central Idaho:

Scientists at Idaho State University have mapped a previously unknown and active seismic fault in the northern Rockies capable of unleashing an earthquake with a magnitude as high as 7.5....

....Glenn Thackray, chairman of the university's geosciences department, said the 40-mile-long fracture in the Earth's crust at the base of the Sawtooth Mountains near the tiny mountain town of Stanley is cause for some concern.

"There's a chance in the next few decades there will be an earthquake on this fault, and if it does happen it will be a rather large earthquake," he said.

Scientists located the fault with a remote sensing technique that relies on laser-equipped airplanes. They were able to gather data about its history by analyzing sediment cores lifted from Redfish Lake, a mountain lake on the fault line famous for its historic sockeye salmon runs.

Thackray said researchers believe the fault triggered two earthquakes over the past 10,000 years, one some 7,000 years ago and another 4,000 years ago, suggesting significant seismic activity occurs at the site every several thousand years.

I visited the fault scarp from the 1983 Mount Borah earthquake this summer (another illustration here). With nearly ten feet of vertical displacement in places, it's quite impressive. The mountains rose six inches while the valley floor dropped nine feet. We run a rapid on the Middle Fork of the Salmon whose main obstacle is a boulder dislodged from the cliffs by the quake 70 miles away. East-central Idaho is shaky country. Quakes here would be a big deal if the area weren't so sparsely populated.

The summer of the year 1783 was an amazing and portentous one, and full of horrible phaenomena; for besides the alarming meteors and tremendous thunder-storms that affrighted and distressed the different counties of this kingdom, the peculiar haze, or smokey fog, that prevailed for many weeks in this island, and in every part of Europe, and even beyond its limits, was a most extraordinary appearance, unlike anything known within the memory of man. By my journal I find that I had noticed this strange occurrence from June 23 to July 20 inclusive, during which period the wind varied to every quarter without making any alteration in the air. The sun, at noon, looked as blank as a clouded moon, and shed a rust- coloured ferruginous light on the ground, and floors of rooms; but was particularly lurid and blood-coloured at rising and setting. All the time the heat was so intense that butchers' meat could hardly be eaten on the day after it was killed; and the flies swarmed so in the lanes and hedges that they rendered the horses half frantic, and riding irksome. The country people began to look with a superstitious awe, at the red, louring aspect of the sun...

--Gilbert White, recalling the effects of the 1783 eruption of Laki on England

While we're all fascinated by the current eruption of Eyjafjallajökull (great pictures!), spare a moment to contemplate Laki in 1783. 20% or more of Iceland's population died of famine, a cloud of poison gas hung about Iceland and Europe over a brutally hot summer, and the following winter was frigid across Europe and America. Puts all those delayed flights in perspective, doesn't it? If Eyjafjallajökull keeps belching, it'll be interesting to see if there are climatic effects, or at least good sunsets.

Of course, it might trigger Katla. Interesting Katla fact:

At the peak of the 1755 eruption the flood discharge has been estimated at 200,000–400,000 m³/s [that's cubic meters! --ed.]; for comparison, the combined average discharge of the Amazon, Mississippi, Nile, and Yangtze rivers is about 266,000 m³/s.

Hat tip: Sailer.

Plumbing of the Yellowstone supervolcano, with a nice 3-D animation.

Happy New Year! As you've no doubt heard, Yellowstone is doing some very entertaining things lately. I must say, it's rather tempting to head up that way: there might be some splendid spectacle to be had, and in the worse case scenario it would be one of the less unpleasant places to be. What would you give to be a fly on the wall of the Church Universal and Triumphant right now?

If you're the type who would enjoy them, Fresh Bilge is posting frequent Yellowstone updates. We're also in his sidebar: rather generous of him, I'd say. I guess he liked my Manzano Mountains post a couple years back. Thanks! Our site meter has been non-functional and ignored for quite a while now, so I have no idea who may have been linking us. Linkers, feel free to say hi in the comments if you like.

Lake Mead: Silt, Superposition & Whitewater

One of the most interesting parts of my recent Grand Canyon trip was floating past the usual takeout at Diamond Creek and continuing all the way to Lake Mead. I'd never seen this lower stretch before, and it was certainly very beautiful and pretty fascinating. I do not, however, recommend it in August: our daily highs were somewhere in the neighbourhood of 115 F.

The water level in Lake Mead is currently very, very low. Note the bathtub ring in the photo to the left (click photos for larger, better versions). This was well out within the theoretical perimiter of the so-called lake, and the ring represents the old average pool. This location is also at least 20 miles dowstream of where my map informed me was current's end at the Lake's historic low. Clearly, we've been breaking records for years and years! To add to the general amusement of the place, there were feral bulls wandering about on the river bank.

Unsurprisingly, the name of the game in the Lake is silt. At the Lake's historic high backwater, still well within the Grand Canyon proper, we began seeing banks of silt covering the river's true banks, and as we continued downstream they grew higher and more extensive. Not infrequently, a section would collapse in our view, avalanching dirt into the river and kicking up prodigious clouds of dust.

Once you come out of the Canyon into the flats, the silt really spreads out, into a vast plain covered in tamarisk and willow, corresponding of course to the shape of the former reservoir. The old takeout at Lake Mead was Pierce Ferry; the Pierce Ferry boat ramp is now over two miles from the river. Thankfully, things are livened up around here by a new rapid which has been forming and changing frequently for the past couple seasons. In addition to providing amusement, the Pierce Ferry rapid also provides a near perfect, small-scale illustration of the principle of canyon cutting by superposition (for a full account, read about the formation of Lodore Canyon here).

What's going on here is that, as the Lake level has dropped, the river was not left with its former basin, but rather with the new expanse of flat silt. Unconstrained by its old banks, which are now deep beneath dirt somewhere, the Colorado could meander over the plain rather freely. In many areas, the river of 2008 is far from its old channel. Of course, the current quickly began cutting down and eroding its silty bed, thus fixing its new course somewhat. But in a couple spots, such as Pierce Ferry Rapid, it hit bedrock outcrops a short ways beneath the surface. In the adjacent photo, the silt plain is clearly visible to the right; the bedrock is forming the boulder in the middle and the pourover and whitewater to the sides where the river flows over it. It's probably being eroded very fast; I'm told the rapid is seldom quite the same from one week to the next. The rapid is also much bigger than it looks in this rather dismal snapshot: for instance, the center boulder is easily 25 feet wide, and the whitewater is plenty capable of flipping a loaded boat.

One of our party running the right channel.

Definitely enlarge this one!

If you imagine a much bigger plain and a lot more bedrock in the picture, it's easy to see how a river becomes entrenched in its own course and incises its meandering path deep into stone.

Also interesting is where the river finally ends. Current's end is not a gradual process at all; it's almost as abrupt as if someone snapped a chalkline across the water. Upstream, the water is brown and cold; five feet downstream, it's green and warm. The silt is still coming, still settling in. You have to see it to appreciate fully the extent of the siltation problems facing Lakes Powell and Mead.

The Colorado comes to a halt.

Also in Grand Canyon news, there's a new theory of its formation just out which deems its age much greater than previous estimates. While the structure of its constituent rock strata is pretty simple, explaining the formation of the Canyon itself has long been very contentious. "If you ever want to see geologists screaming at each other," an informed person once told me, "ask them to interpret the Grand Wash Cliffs Formation." We'll see how the new theory holds up long-term.

Oh, very well. Last night's post inspired me to spend a little more quality time with the scanner before packing it away. Let's put proper closure on the Grand Canyon photos. First, another shot to make you wish you lived at Havasu:

The western Grand Canyon is vast, harsh and very little explored away from the river, especially in summer. The heat is satisfyingly punishing, frequently reaching the 110-115 degree range. One of our group reported that when he woke up at 2:00 in the morning, his watch thermometer still read 99. The heat is frequently accompanied by winds, intensifying the blast furnace effect and bereft of the slightest trace of moisture. Straying far from the water is intolerable; sometimes one has to get soaking wet in the evening to get to sleep, and even repeat the procedure after an hour or two. It's a very satisfying desert experience.

An action shot from Mrs. Peculiar, yours truly on the oars:

Another notable difference between the lower Canyon and the more frequently depicted upstream sections is the presence of lava. In the very recent geologic past, a number of volcanoes burst out of the Uinkaret Plateau, which forms the northwestern rim of the Canyon and is one of the most remote chunks of the lower 48. The Grand Canyon already existed in pretty much its present form, and the lava flows ran southward and dropped off the rim. In some areas you can see clearly where the lava flowed between butresses in the walls and around obstacles. A more dramatic spectacle of geology is hard to imagine!

(Note the darker rocks forming a horizontal band at center: that's the lava.)
Despite the post-apocalyptic heat and dryness, the area is subject to punishing thunderstorms, such as this one from our last night on the river:

These storms in the lower Canyon are a significant source of anxiety for boaters, inasmuch as the takeout road up Diamond Creek is notoriously eager to flash flood. A friend of mine once witnessed two commercial outfits' vehicles, Mack truck-sized rigs, being rolled over and over in a debris flow accompanied by plenty equally large boulders. They're in Diamond Creek Rapid now, along with numerous others, no doubt.

Fortunately for us, damage to the road was minor and only delayed our shuttle vehicle by an hour or so. Here's the scene, with us and two other parties waiting for our rides. The creek and I are both in the middle of the road.

Stay tuned: one more photo post to come.

Mrs. Peculiar and I are undergoing the dubious joys of moving presently, gearing up for six months or more of sweet seminomadism. As I'm not of the type who has WiFi devices implanted in his body, nor any similar arrangements, my days of regular blogging are numbered, numbered to about four, to be precise. (Incidentally, the next person who pesters us about an infernal cell phone, because, "How, oh how, will all and sundry keep in constant, pestersome touch?", is highly liable to lose the tip of her nose.) Therefore, here is a last set of Grand Canyon photos.

The Grand Canyon is well known for it's whitewater, but the rapids are remarkably difficult to catch on camera without highly inconveniencing everybody. But to give you an idea, here's a shot of Granite from a trip several years ago:

Here's Mrs. Peculiar beside Tapeats Creek, an intursion of moist lushness into a vertical, stony desert:

A major tributary of Tapeats Creek is Thunder River, which bursts out of a hole in a limestone cliff and cascades without delay straight down the side of the Grand Canyon. Click to enlarge, and note the three hikers just left of center for scale:

Looking back towards Tapeats from Thunder Spring. Our more geologically astute readers will note a visibly slanted pink layer at the canyon bottom. That is Shinumo Quartzite; it and its siblings of the Grand Canyon Supergroup were laid down flat in Proterozoic times, tilted to their present angle, eroded, and then covered with Tapeats Sandstone at the bottom of a Cambrian sea, followed by the many, many other sedimentary layers of the Colorado Plateau:

A little downstream from Tapeats, Deer Creek falls from a sandstone slot 150 feet into the Colorado. Sorry about the lack of scale; a person at the base of the falls would be treading about eight feet of water in the pool while being peppered with bullets of spray:

Finally, a shot of the idyllic Havasu Creek. Everyone on earth would want to live there if it weren't scoured by 20-foot walls of water every decade or so:

I do have some worthwhile shots of the less-photographed lower canyon, but they aren't scanned and I'm not optimistic about making that happen by Sunday.