The Cline Buttes are mountains with volcanic origins that form three dome-shaped peaks located in Deschutes County in central Oregon. They are some of the eastern foothills of the Cascade Range. Situated on land administered by the Bureau of Land Management, the buttes are flanked on the east and west sides by two separate sections of the Eagle Crest Resort. On the highest summit, there is a Federal Aviation Administration site with an aircraft navigation beacon. The mountains have several hiking trails as well as a number of popular mountain bike routes. Geography and geology The Cline Buttes are composed of three rounded peaks. They are some of the easternmost foothills of the Cascade mountain range, located near the northwest corner of Oregon's high desert country. The mountains are in Deschutes County, approximately west of Redmond. Of the three crests, the southern peak is the highest. Its summit is above sea level. The Cline Buttes are a stand-alone mountain with the nearest higher peak to the south. Cline Buttes feature gentle slopes with highly conical shaped peaks. The Cline Buttes form a silicic volcanic center, active before the emplacement of the Deschutes Formation, a late Miocene to early Pliocene volcanic lava flow deposited between 7.5 and 5.3 million years ago. Their lava flows cover a collective area of approximately , and were created as part of the John Day Formation during the late Oligocene or early Miocene epoch, approximately twenty-five million years ago. The primary rock that makes up the mountain is rhyolite with some basalt also present. Most of the rhyolite is white or light-gray. It was formed when volcanic magma cooled below the earth's surface before erupting onto the surface. There are also some obsidian flow-bands exposed in a rock quarry on the northeast flank of the mountains. The Cline Buttes have been significantly eroded over time, leaving a rounded dome shape with three separate crests. They are now covered with of sandy loam soil in most areas with rhyolite and basalt outcropping on the steeper slopes. The rhyolite lava flow deposits at Cline Buttes show a roughly porphyritic texture, with oligoclase phenocrysts making up between 1 and 2 percent of the minerals. These flows have been devitrified and show a normal-polarity magnetization. Cline Buttes volcanoes also produced rhyodacite, which varies in color from light gray to red-brown and are similarly sparsely porphyritic. The basalt lava flows produced