A slice through Earth’s mantle under the Andes. © Jonny Wu, University of Houston

The Answer Is Blowing in the (Mantle) Wind


Geology went through a Kuhnian revolution in the 1960s and 1970s, with the emergence of plate tectonics as an explanation, as a mechanism, driving what geologists were observing in the field. Plate tectonics has settled in as a credible, definitive and confirmable explanation of everything from vulcanism to oceanic trenches. But it’s also an incomplete…

Granodiorite, with an intrusive vein of quartzolite, Payette River canyon, Idaho

Geology 101: Granite Is Hard!


Non-geologists think of granite as – sorry – monolithic. Igenous rock that cools underground, right? You know, as opposed to lava, which cools on the surface. Well, geology is messy. And granite is messy, even for geology. Yet the kind of “granite” matters, because the chemical composition of rock determines how it weathers, how quickly…

Idaho Batholith at Lick Creek Summit, northeast of McCall, Idaho

Geology Is Messy: The Idaho Batholith


The Idaho Batholith is a vast chunk of granite that dominates central Idaho. It’s some 15,400 square miles of rock. People talk about it as if it’s a gigantic, homogenous lump of stone. It’s not. Geology is complicated. Most, but not all, geologists agree the Batholith was formed when the Pacific Plate subsumed under the…

A schematic model that links the slab hole with other physiographic features. The view is from the east, and theJuan de Fuca slab is shown in blue. The propagator wake (bold gray line underneath Oregon) causes a weakness in the slabalong which a tear is propagating. The High Lava Plains (contours in Oregon) lie above the southern edge of theslab hole. The Gorda slab rotates clockwise, causing intraplate seismicity in the Gorda region.

Untangling Oregon Volcanism


Most of Oregon is igneous rock. Pretty recent igneous rock, as geologists measure time. It’s almost embarrassing. While some of it is pretty well understood, parts of all that volcanism are unexplained. The stratovolcanoes of the High Cascades? Subduction of the Juan de Fuca Plate and Pacific Plate. The lava that flowed into the Pacific…

Acipenseriform fish with ejecta clustered in the gill region. (A) X-ray of a fossil sturgeon head (outlined, pointing left; FAU.DGS.ND.161.115.T). (B) Magnified image of the X-ray in A showing numerous ejecta spherules clustered within the gill region (arrows). (C and D) Micro-CT images of another fish specimen (paddlefish; FAU.DGS.ND.161.29.T), with microtektites embedded between the gill rakers in the same fashion.

The Best Evidence Yet for the Dinosaur Killer


Archaeologist Robert A. DePalma, working in Southcentral North Dakota, has found the best evidence yet that the dinosaur killer, the huge meteor that struck the Yucatan Peninsula, leaving the Chicxulub crater, did indeed kill the dinosaurs. He has found, entombed in the rocks of the Hell Creek Formation, the archaeological equivalent of a smoking gun.…

Wright's Point from the east; photo credit Twilight, via Creative Commons License

Geology 101: Inverted Topography


As you drive south across the Harney Basin on Oregon Highway 201, you can’t miss Wright’s Point. The very long, very narrow, steep-sided ridge sticks out 10 miles into the basin, rising 250 feet above the flat lakebed. The much-diverted Silvies River loops around the easterly end of Wright’s Point, headed further south to Malheur…

The Other Crater Lake


WC is back from a week-long trip to the easterly side of the Oregon Cascades, where the scenery is very, very good but services do not include internet. This is the first of several posts from the trip. Crater Lake, in the Oregon Cascades, is justly famous. That remnant of Mt. Mazama is a near-perfect…