The time was about 600,000 years ago, and the place was an area now known as Yellowstone National Park. Magma pulsing upward through the earth’s crust caused the land at the planet’s surface to bulge upward. Then at a point when the overlying rock could no longer contain the pressure from the magma, cracks formed opening up vents from the surface to the magma chamber. The pressure release was catastrophic, causing the uncontrolled ejection of gases, fluids, and magma up to 30 miles into the atmosphere.
During the eruptions, more than 240 cubic miles of rock, dust, and ash emptied from below Yellowstone. Associated ash fallout covered much of the USA. The evacuation of this much material from the magma chamber below Yellowstone then caused the remaining surface rock to collapse. This collapse formed the present-day caldera that characterizes the geomorphology of the park.
The pulse of magma leading to the Yellowstone eruption forms the Yellowstone hotspot. So, hotspot refers to the surface location of a mantle plume of molten rock that rises hundreds of miles to the earth’s surface. Hawaii and Iceland are also examples of hotspots.
The Yellowstone National Park has not always been located over a hotspot. The mantle plume responsible for this hotspot originates below the North American plate. So, the surface expression of hotspot volcanism changes as the plate moves over the hotspot. This process then creates a linear progression of surface volcanic eruptions that trace back to Eastern Oregon.
Some researchers believe that the Yellowstone mantle plume was the source for the Columbia River Basalts. These basalts originated from lava flowing out of large fissures in Eastern Oregon about 16 million years ago. Individual fissures were up to 17 kilometers long. These fissures literally formed cracks in the earth’s crust. When the cracks opened, molten lava from the earth’s interior poured onto the surface and flowed like water.
However, the lavas didn’t mound up to build volcanoes. Instead, they flowed as sheets of liquid rock covering the landscape. The Grande Ronde Basalts were the most extensive of all the basalt flows. A total of 120 individual lava flows compose the Grande Ronde Basalts. Today, the lava flows stack on top of each other like sheets of paper, and individual flows are tens to hundreds of feet thick. The Grande Ronde basalt flows stretch from Idaho to the Pacific coast. Also, these lava flows cover large portions of Western Idaho, Southeastern Washington, and Northern Oregon.
The land still breathes
Ongoing research in Yellowstone National Park finds that a large area to the northwest of the caldera is inflating and deflating over time. Satellite-based observations track this “breathing” process in the Norris Geyser Basin. The inflation and deflation also have accompanied increased geyser activity in the area over the past 20 years.
One of the explanations put forward for this “breathing” is that in the 1990s, a magma body intruded below the Norris Geyser Basin. Then as fluids from the magma tried to escape, they become trapped, and the chamber area inflated. This inflation caused the rock over the magma chamber to uplift. When the fluids finally escaped, then the chamber deflated slightly, and the land surface fell.
This “breathing” effect emphasizes how geologically active the Yellowstone area is. Hotspots, in general, provide real-time views of geology in action. Events that occur over millions of years are a bit abstract. However dramatic events that occur over hotspots occupy timespans of only days to decades. We can see them play out over the span of a human lifetime, thus making them seem more real. So, the Yellowstone National Park’s geological interaction with the atmosphere, hydrosphere, and
The Icelandic Plume (Source: ArcheanWeb) – https://archeanweb.com/2020/03/25/the-icelandic-plume/ Also:
The Axial Seamount: a very active volcano (Source: ArcheanWeb) – https://archeanweb.com/2020/03/20/the-axial-seamount-a-very-active-volcano/ Also:
A chunk of Yellowstone the size of Chicago has been pulsing. Why? (By ROBIN GEORGE ANDREWS; National Geographic) – https://www.nationalgeographic.com/science/2020/03/chunk-yellowstone-size-chicago-has-been-pulsing/ Also:
How the Yellowstone Caldera Formed (Source: Yellowstone National Park Service) – https://www.yellowstonepark.com/things-to-do/how-the-yellowstone-caldera-formed Also:
Origin of the Columbia River Basalt: Passive ascent of
Feature Image: Steam Phase eruption of Castle geyser with double rainbow (By Brocken Inaglory) (Modified) – https://commons.wikimedia.org/wiki/File:Steam_Phase_eruption_of_Castle_geyser_with_double_rainbow.jpg – This file is licensed under the Creative Commons Attribution-Share Alike 3.0 Unported, 2.5 Generic, 2.0 Generic and 1.0 Generic license.