Geological History of the Palouse-by Chip Phillips

 

 

 

 

 

 

 

 

 

 

 

Recently my wife and I were on Steptoe Butte, looking down into the vast rolling expanse of the Palouse below us. She wondered out loud how the Palouse came to look the way it does. “It was glaciers, right?” she said. “It must have been glaciers.”

 

Actually, glaciers played a role, but not in the way she thought. A couple billion years ago, the Palouse was a shallow sea. Quartz sand was deposited then. Over time, the sand was covered by sediments and became solid sandstone. Gradually, helped by being heated in the earth, the quartz sand became hard rock known as quartzite. Steptoe and Kamiak Buttes are made up of this ancient quartzite, and they tower above all the surrounding younger geological formations.

 

Fast-foward to 15 million years ago, when large eruptions of iron-rich lava engulfed the Palouse. The lava covered everything except the highest buttes, killing all the plants and animals in its wake. These eruptions formed layers of dark rock called basalt, which is still visible in many places today.

 

1.6 million years ago was the beginning of the Ice Age. From then up until only 10,000 years ago, glaciers covered the Palouse, reaching down from Canada. During this Ice Age, strong winds blew across the Palouse, carrying large volumes of silt. This silt, ground to a fine powder by glaciers, is known as loess. Most of the world’s best agricultural soils are in loess. When this silt settled, it formed the rolling, dune-like hills of the Palouse, with their rich topsoil.

 

So, next time you are up on top of Steptoe Butte, think of all the millions of years it took to create such a unique and spectacular place.