Floods of Fire - Oregon Historical Markers on Waymarking.com

Sign about Miocene flood basalts at Mascall Formation Overlook.

Marker Name: Floods of Fire
Marker Text: ”You cannot travel anywhere in Oregon without encountering the Miocene, from 24 to 5 million years ago....In the nearly 20 million years of the Miocene, more lava probably flowed across the Oregon landscape than had erupted here in all the time before and all the time since.”
A major geologic event of the Miocene Epoch began 17 million years ago. The Columbia River Basalt Group eruptions occurred in phases and in several locations. Hundreds of basalt floods issued from scores of fissures in the earth’s crust covering over 62,000 square miles of ancient Oregon, Washington, and Idaho. Below Yakima, Washington, the basalt layers are over 15,000 feet thick.
Some of the floods were so fluid and of such volume that they reached the ocean. Each fiery deluge would have had a dramatic effect on local plants and animals.
Massive plumes of magma were powerful enough to push up and crack the crust in several places. Floods of lava then flowed from the fissures covering the land.
Evidence suggests that the magma plumes may have been generated by, or fed by, a hotspot deep in the earth, perhaps the same hotspot that currently lies below Yellowstone National Park.
The layers of flood basalt before you, in Picture Gorge, are about 1,000 feet in thickness. The layers in the gorge are now tilted, but they were horizontal when first formed 16 million years ago.

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