The Grand Canyon of the Yellowstone (2011). Photo taken from the Artist Point Trail.
Scientists think the oldest Grand Canyon of the Yellowstone formed in rock and sediments about 160,000 to 140,000 years ago. This canyon was not as deep, wide, or long as today’s canyon.
Past and current hydrothermal activity altered and weakened the rhyolite, making the rocks softer. The Yellowstone River eroded these weakened rocks to deepen and widen the canyon, a process that continues today. The current canyon begins at the Lower Falls (seen in the photo) and ends at Tower Fall.
The colors are caused by oxidation of iron compounds in the rhyolite rock, which has been hydrothermally altered ("cooked").
The colors indicate the presence or absence of water in the individual iron compounds and hydration of minerals in the rock. Most of the yellows in the canyon result from iron and sulfur in the rock. Dark orange, brown, and green areas near the river are still active hydrothermal features. [Source: U.S. National Park Service]
The Grand Canyon of the Yellowstone (2011). Photo taken from the Artist Point Trail.
Scientists think the oldest Grand Canyon of the Yellowstone formed in rock and sediments about 160,000 to 140,000 years ago. This canyon was not as deep, wide, or long as today’s canyon.
Past and current hydrothermal activity altered and weakened the rhyolite, making the rocks softer. The Yellowstone River eroded these weakened rocks to deepen and widen the canyon, a process that continues today. The current canyon begins at the Lower Falls (seen in the photo) and ends at Tower Fall.
The colors are caused by oxidation of iron compounds in the rhyolite rock, which has been hydrothermally altered ("cooked").
The colors indicate the presence or absence of water in the individual iron compounds and hydration of minerals in the rock. Most of the yellows in the canyon result from iron and sulfur in the rock. Dark orange, brown, and green areas near the river are still active hydrothermal features. [Source: U.S. National Park Service]