our Convergence of Wonders, the geological tour of the Pacific Northwest and Northern Rocky Mountains. It was June 30th. We had traveled through the Cascades and the Coast Ranges, the present-day manifestation of convergence along the Cascadia Subduction Zone. We had traveled across the Columbia Plateau and the Channeled Scablands, and looked at evidence of past convergence in Montana's Glacier National Park, and Sun Canyon. We explored the inner parts of the earth's crust along the Beartooth Highway, and saw the evidence for a gigantic mantle plume (hot spot) at Yellowstone National Park. We saw the vast heavings of fault lines in the crust at Grand Teton National Park. And now, after a series of adventures in Utah and Nevada, we were finally headed home.
In the most technical sense, we could have started driving and made it home for a late lunch. But we couldn't pass up several of the most spectacular geological sights of our trip. We were almost home, but we could still be distracted by geological sights!
When we arrived at Berlin-Ichthyosaur State Park very late the previous night, not a few of our students were just a bit spooked by finding we were spending the night in a ghost town. The menacing looking ruins of the dark night were a little less nerve-wracking in the morning sun, so we packed and headed up to the quarry for a tour. Berlin-Ichthyosaur is a two-fer park: it preserves a late 1800's gold mining town, and a 200 million year old paleontology dig.
One of the mysteries is why so many of the ichthyosaurs ended up dead in this one place. Numerous ideas have been suggested, including strandings, volcanic eruptions, spawning behaviour and others, but the favored explanation of the moment based on available evidence is that they died from mass poisoning, much as marine animals are killed today by red tides (toxic microorganisms). For more information on the topic, check out vignette 14 in Geology Underfoot in Central Nevada, by Orndorff, Wieder and Filkorn.