There’s no easy way to summarize the geology of Southeastern Arizona except to describe it as a complex mess. WC doesn’t want and isn’t qualified to write the multi-volume treatise that would be required to begin to detail it. So here is the briefest possible summary of about 1.4 billion – that’s billion with a…
WC if off birding. Again. Internet access will be only intermittent. There may be delay in approving comments or responding to emails. There’s some very interesting geology in Oregon; unfortunately, it’s all buried under 2,000 feet of basalt. – Eldridge Moores Moores was being ironic when he said that to WC’s geology class in 1971.…
The jet flight from Anchorage to Juneau, on a clear day, offers some of the most spectacular country in the world out your cabin window. The problem is, there aren’t that many clear days on the Gulf of Alaska. WC got lucky in August 2015. Here’s a flight-seeing guide to just some of the amazing…
As geologic hot spots or mantle plumes go, the Bowie Hot Spot isn’t exactly a gusher. The Hawaii hot spot may have produced Mauna Loa and Mauna Kea, the tallest mountains, measured from the base, on Earth. That’s a whole lotta lava. The Bowie Hot Spot has yet to break through sea level.1 The Bowie…
It’s easily the most famous April Fool’s Day practical joke in Alaska history. The late Porky Bickar, of Sitka, Alaska, and a group of assistants, who mostly prefer to remain anonymous, helicoptered a couple of hundred old tires, some diesel fuel and a sterno can to the crater of Mt. Edgecumbe, an inactive volcano about…
There’s no easy explanation for the Bolaven volcanic field in southeast Laos. Geology understands three things can create volcanism: (1) subduction nearby, forcing one tectonic plate under another; (2) a mantle plume, a “hotspot” like the Yellowstone plume; or (3) extensional faulting, as in the basin and range province in the western U.S., where the…
Geologists generally agree that “cratons” are the older and more stable part of continental plates. Most geologists think cratons have two parts, a shield and a platform. The shield is usually characterized by deep lithospheric roots; the shields in continental tectonic plates are usually much thicker, two to four times as thick, as their cousin…
The Earth’s geologic history goes back about 4.6 billion years. The first few hundred thousand years, the rock was mostly molten. Igneous rocks, rock cooled enough to be a solid and not a liquid, are believed to have started appearing about 4 billion years ago. The oldest rocks so far found are in the Canadian…
You knew, or should have known, that there would be a McPhee book in this set of five books that strongly influenced WC. The only question was which one to choose. WC’s short list was eight books long. But WC settled on Assembling California because it is the best of his four volume geology series…
It’s been more than a month since Wickersham’s Conscience had a geology post. And while geology isn’t the most popular topic among WC’s readers, everyone needs a break from Brazilian birds, politics, impolitics and economics. Ick. “Tuff” is an igneous rock created by volcanic ash and tephra. In the Mountain West, almost all tuff is…
In 1967, W. Jason Morgan, a physicist, stood before the annual meeting of the American Geophysical Union to present a paper on the Puerto Rican Trench. Except he announced he would speak on something else, instead, ” Rises, Trenches, Great Faults and Crustal Blocks.” What he did in the substitute presentation was lay out the…
All specialties have their own vocabularies. Geology’s vocabulary can be particularly obscure. If you are trying to read a geology paper and encounter “antiformal metasyncline,” for example, the MEGO Factor can get pretty intense.1 “Fluvioglacial” or “glaciofluvial” means erosion or deposition caused by flowing meltwater from glaciers, ice sheets and ice caps. Glacial meltwater is usually very…
With any luck, this is the first time “hotrod” and “cratons” have been used in the same sentence, let alone in a title, of an article purportedly about geology. But there is some evidence that in the Neoarchean, a geologic era some 2.7 to 2.5 billion years ago, a portion of modern day Australia was…
Okay, this is pretty abstruse, even by the sloppy standards of Wickersham’s Conscience. But part of the challenge of living on the Last Frontier is that human time intersects geologic time in Alaska. Earthquakes, permafrost melt, isostatic rebound . . . Wait, what? WC has written earlier about isostatic rebound, the geologic process by which…
WC has written about Steens Mountain before, but the photos were pretty awful; California wildfires had laid a thick blanket of smoke over the area, so dense that from the summit of the mountain you could not see the Alford Desert 5,500 feet below. So WC will re-visit that amazing place, this time with somewhat…
Nestled along the westerly bank of Warm Springs Creek off of Idaho State Highway 21, Bonneville Hot Springs is a “primitive” – i.e., undeveloped – hot spring in Boise National Forest. It’s an easy quarter mile walk from a parking lot about a mile off of the state highway. It’s a pretty magical place. The…
There’s a remarkable rock formation in central Idaho. In the midst of all the granodiorite that makes up the Idaho Batholith, on top of the ridge above the fabulous Burgdorf Hot Springs, there’s an immense, beautiful and astonishing outcropping of quartz. Quartz is Silicon Dioxide, SiO2, one of the most common minerals in the Earth’s…
Leslie Gulch in east-central Oregon is a little-known geological wonder, a deeply dissected jumble of volcanic debris with jaw-dropping rock formations. For an amateur geologist, it’s also an irresistible puzzle. There are folks who criticize attempts to understand the geology of a scenic spot like Leslie Gulch, claiming it takes the wonder out of the…
For a long time, really since the first Mars probes, the Red Planet was thought to be geologically dead. Sure, there were extremely impressive geologic features that showed Mars had been geologically active in the past. It’s hard to argue that point when there’s the volcano Mons Olympus that’s more than 21 kilometers tall (2.5…
The chemistry of magma – molten rock – is unbelievably complex and only incompletely understood. In the case of the suite of minerals called plagioclases, it’s more accurate to say it is barely understood. It’s cheeky for a guy who slept through Mineralogy to even attempt to describe this,1 but when has that ever stopped…
WC recently spent a few delightful days birding in Summer Lake Wildlife Refuge, in southcentral Oregon. Because it all starts with geology, WC will start there, too. Multiple geology theses, a few books and hundreds of geology papers have been written on Summer Lake and its ancestor, Chewaucan (chee-WAU-can) Lake. WC is necessarily going to…
Long-time readers know WC gets twitchy if there isn’t a geology post for a while. The geology and geomorphology of Florida, where WC was most recently, is frankly boring. Missouri, WC’s other recent destination, was all about the ages of layers and layers of limestone. Boring.1 So WC will reach back to his trips into…
Most readers know about the Yellowstone Mantle Plume, the “hot spot” that has given us the Yellowstone caldera and, not long ago in geologic time, some very scary eruptions. The mantle plume is the source of the heat that makes Yellowstone National Park what it is today. Research on the geologic history of the mantle…
The Hagerman Formation, a layer of sand and silt compressed to fragile sedimentary rock, is part of the larger Idaho Group. It’s world famous as the source of the Hagerman fossils. A large piece of the Formation is preserved as the Hagerman Fossil Beds National Monument, which has produced thousands of fossils across more than…
WC was able to challenge Geology 101 – 103 and so missed the introductory geology courses at the University of Oregon, derisively called “Rocks for Jocks.” “Challenge”? Maybe that’s no longer a thing. But back in the late Pliocene, when WC was an undergraduate, you could meet the course requirements of any entry level science…
The most powerful earthquake to strike Turkey in the last hundred years has caused incredible damage and loss of life in southern Turkey and Syria. It’s instructive to look at the underlying geology, because it has important lessons for folks living along the San Andreas Fault. The earthquake and aftershocks are along the East Anatolian…
You probably think of sand dunes as a desert phenomenon. But you can get sand dunes wherever you have (1) a decent supply of coarse-grained sand, (2) an area where there is enough topography to create a trap for the sand, and (3) relatively equal distribution of the winds, or at least no prevailing single…
About 56 million years ago, the Earth experienced something called the Paleocene-Eocene Thermal Maximum (PETM). The Earth’s atmosphere warmed by about 6.5° C, and sea surface temperatures by about 5° C. There was serious ocean acidification, which is associated with very high CO2 levels in the atmosphere. It’s too long after the Dinosaur Killer’s cataclysmic…
WC has read two lay geology books recently, and the contrast in their approaches to the rocky science is itself instructive. Both are fine examples of cogent, readable explanation of geology, in this case the geology of the Great Basin. The first is Frank DeCourten’s The Great Basin Seafloor, which is a geologic history of…
In the late 18th and early 19th Centuries, there was a mighty struggle in the nascent science of geology. Biblical literalism had insisted on a young earth, created less than 10,000 year earlier, and a literal, world-spanning Noachian flood. As the evidence for a much older earth accumulated, and the evidence against a global flood…
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