Basalt of the Narrows
Visible from the Tower Fall overlook in Yellowstone national park are two dark, horizontal layers of columnar basalt. These striking columns formed as lava cooled and contracted. The flows, known as the Basalt of the Narrows, erupted about 1.3 million years ago—around the same time as the second caldera-forming eruptions that created the Henrys Fork Caldera, southwest of Yellowstone in eastern Idaho. This caldera was the second of three in the Yellowstone area. The two basalt layers are separated by a thick accumulation of gravel, including glacial deposits, and are capped by additional glacial debris.
Basalt of the Narrows
Visible from the Tower Fall overlook in Yellowstone national park are two dark, horizontal layers of columnar basalt. These striking columns formed as lava cooled and contracted. The flows, known as the Basalt of the Narrows, erupted about 1.3 million years ago—around the same time as the second caldera-forming eruptions that created the Henrys Fork Caldera, southwest of Yellowstone in eastern Idaho. This caldera was the second of three in the Yellowstone area. The two basalt layers are separated by a thick accumulation of gravel, including glacial deposits, and are capped by additional glacial debris.