TLDR: Colorado’s supervolcanic eruptions 28 million years ago formed large calderas and ignimbrites, preserved fossils, and showed remarkable ecosystem resilience.
This article is a summary of a You Tube video “That Time the American West Blew Up” by PBS Eons
Key Takeaways:
- Epic Scale Eruption: 28 million years ago, Colorado experienced a massive volcanic eruption, resulting in a caldera 8 times larger than Denver.
- Formation of Ignimbrite: The eruption produced vast amounts of ash that solidified into a rock known as ignimbrite.
- Fish Canyon Tuff: This particular eruption, known as the Fish Canyon Tuff, released material double that of Yellowstone’s largest eruption and 5000 times more than Mt. St. Helens in 1980.
- Mid-Tertiary Ignimbrite Flare-up: This event was part of a series of supervolcanic eruptions that occurred in the western US, known as the Mid-Tertiary Ignimbrite Flare-up.
- Geological Impact: These eruptions left significant geological marks but did not cause major extinction events, contrary to what might be expected.
- Preservation of Fossils: The period saw significant fossil records being preserved, like the John Day Fossil Beds in Oregon.
- Plate Tectonics: The eruptions were linked to the interaction between the Farallon and North American plates, with the slow sinking of the Farallon plate contributing to unique volcanic activities.
- Silica-rich Magma and Explosive Eruptions: The nature of continental plates led to silica-rich magma formations, causing more explosive eruptions.
- Ecosystem Resilience: Despite the scale of the eruptions, ecosystems adapted and recovered, with studies showing rapid regrowth and animal population recovery post-eruptions.
- Fossil Formation in Calderas: The supervolcanoes contributed to the formation of rich fossil deposits in their calderas, providing valuable insights into ancient life.
