What will happen when the \¨supervolcano\¨ under Yellowstone National Park finally erupts? I've seen some sites prognosticating mass extinctions and the end of civilization as we know it. I suggest that you take a deep breath and calm down. Eastern Oregon had some of the most intense volcanism of the Cenozoic and yet life went on. You should come to Grant County Oregon and see the evidence for yourself.The geology of Oregon is extremely complicated and I am not a geologist so this a highly simplified version: In the age of the dinosaurs most of what is now Oregon was ocean. In the next 200 million years various islands were shoved against the western edge of north America to make up what is now the lowest layer of this landscape.Possibly due to this basement layer being thinner than the rest of the continental plate, Oregon has had more than its fair share of volcanic activity.If you search on \"Yellowstone hotspot\", you will find that, due to the motion of the north American plate, 17 million years ago the Yellowstone hot spot was under the southeastern corner of Oregon. At the same time, several hundred miles north of here, thousands of square miles were being covered by Columbia River flood basalts thousands of feet thick.But all the ash and lava deposits in these pictures are from completely separate volcanic events. The red soil in the foreground is ash from volcanoes to the west of here. The buff colored outcrops in the middle distance is more recent volcanic ash deposits from a different source and the tops of the hills in the distance are formed of Picture Gorge basalt from vents nearby.Here is a view showing the most recent ash deposits and the lava flows above them. The green-grey bluffs are ash from volcanoes south of here and the reddish layers of rock in the far hills are Picture Gorge basalt. The herd of cattle at the base of the bluff should give you some sense of how thick the accumulation of volcanic ash is. I hereby offer the \"cow for scale\" as a new internet standard for cases when \"banana for scale\" is inadequate. Note that the cattle in this picture are US Customary Cows and therefore 7.166 bananas rather than the 7.183 bananas which would be the case with metric cows. In any case it is obvious that a great deal of volcanic ash has fallen in this region. Then after the ash eruptions were over, we had a repeated series of lava flows. I count at least seventeen distinct layers here and there may be more. Note that these are distinct from the Columbia River basalt flows about 100 miles north of here which were much thicker and covered thousands of square miles. Finally, about 7 million years ago, what was then the valley floor, was filled with the last bit of volcanism: the Rattlesnake Ignimbrite. This was a pyroclastic flow which originated eighty miles to the south and incinerated all in its path and which was still hot enough when it got here to fuse the ash into a solid mass. As you can see from this picture sometime after the ignimbrite was laid down, we had an earthquate strong enough to vertically displace one side of the valley about 50 feet relative to the other side. Between the phases of active volcanism, life went on and even thrived. The plant and animal life that lived in the shadow of these volcanoes was so abundant that today the John Day Fossil Beds is one of the richest Cenozoic fossil sites in the world. So, yes if the Yellowstone hotspot blows again we will definitely notice and it will probably do a lot of damage. But here in eastern Oregon we've seen thicker ash and more lava over a much longer span of time and that period is now called the \"Age of Mammals\". I think we'll manage.
Grant County Gazette Masthead
Supervolcano Tourism
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