Oregon Magazine

Simon Says:
Geologists Have Rocks in Their Heads

Part One: the basic geological areas

Oregon is a fascinating state for the study of geology. Its varied landscape provides a lifetime of research and enjoyment. In fact, this state is so diverse that many of its own residents are unaware that virtually every form of land known to Earth is available here, to say nothing of outsiders (who are convinced the entire state is swathed in clouds and rain all year long). Oregon’s weather is shaped by its geology, as are its people and its ecosystem.

  While discussing culture, biology and weather are outside the scope of this column, I will, over the next nine months, attempt to acquaint you with each unique geologic province of this great state. Each month I will devote this column to one region and describe it in some depth. For this month, let me briefly explain each area. By next April, when the snows are melting in the Cascades, I hope you will be ready and excited to explore our great state of Oregon.

Oregon’s Geologic Regions – A Brief Overview

                         Oregon has nine distinct regions. Each one was formed by different means and each one has its own unique environmental conditions. Here, then, is a short list of each one, to be explored from West to East over the coming months:          Coast Range: Formed when a volcanic island chain combined with North America 50 million years ago.

           Klamath Mountains: A series of metamorphic and igneous mountain chains that formed as islands and then collided with North America 150 million years ago.

            Willamette Valley: Not formed by the Willamette River, this area is simply lowlands between the Coast Range and Cascades Mountains that collects sediments as they erode from the two mountain ranges.   

Cascade Mountains: These mountains are actually two ranges, older and younger, also known as Western and High Cascades, respectively. The High Cascades contain still-active volcanoes.

Deschutes – Columbia: This area formed when a huge fissure opened along the Washington – Oregon - Idaho border and poured enormous amounts of lava into the area. The cooled and hardened basalt rock is thousands of feet thick in some areas.                                                            

Blue Mountains: These mountains formed off of North America and, like the Coast Range and Klamath Mountains, eventually collided with the continent.

 High Lava Plains: Formed by volcanic activity when the state’s active volcanoes were farther east than their present day location.

Basin and Range: Fault block mountains and valleys that formed when the area was stretched by tectonic movement.

 Owyhee Uplands: Formed in the same fashion as the Basin and Range province, this area is actually part of the Great Basin, which is centered mainly in Nevada. It is separated from the Basin and Range province because, instead of containing enormous fault block mountains and valleys, it is more of a large, flat plateau.

(Graphic by Bailey Roe)
As you can see from the brief list here, Oregon’s geologic provinces are quite diverse. I hope over the next several months that you will enjoy learning about each region in more detail. Each month’s column will include photographs and firsthand accounts of the area as I explore it personally. See you here next month!


© 2009 S. Skiles