Malheur Butte

Malheur Butte is an extinct volcano located in Malheur County, Oregon. Between 20 and 15 million years ago, the region from north-central Washington to northeastern California experienced a series of volcanic eruptions and basalt lava floods that covered thousands of square miles. These ancient lava floods often dammed streams, creating lakes and swamps that may have lasted for millions of years before filling with sediment or draining as erosion slowly lowered their outlets. The western Snake River plain contained many such lakes, and geologists believe that between 8 and 2 million years ago, "Lake Idaho" covered much of central eastern Oregon. Sediment deposited in this lake once covered Malheur Butte, and during the last 2 million years the Malheur River and other eroding forces slowly exposed and shaped today's landmark.

Although Malheur Butte has been inactive for millions of years, Malheur County is still alive with geothermal activity in the form of hot springs.