Jon Burch Photography
Photograph - Digital Capture
Mount Hood, called Wy'east by the Multnomah tribe, is a stratovolcano in the Cascade Volcanic Arc of northern Oregon. It was formed by a subduction zone and rests in the Pacific Northwest region of the United States. It is located about 50 miles (80 km) east-southeast of Portland, on the border between Clackamas and Hood River counties. In addition to being Oregon's highest mountain, it is one of the loftiest mountains in the nation based on its prominence.
The height assigned to Mount Hood's snow-covered peak has varied over its history. Modern sources point to three different heights: 11,249 feet based on the 1991 U.S. National Geodetic Survey, 11,240 feet based on a 1993 scientific expedition, and 11,239 feet of slightly older origin. The peak is home to twelve glaciers. It is the highest point in Oregon and the fourth-highest in the Cascade Range. Mount Hood is considered the Oregon volcano most likely to erupt, though based on its history, an explosive eruption is unlikely. Still, the odds of an eruption in the next 30 years are estimated at between 3 and 7 percent, so the USGS characterizes it as "potentially active", but the mountain is informally considered dormant.
Timberline Lodge is a National Historic Landmark located on the southern flank of Mount Hood just below Palmer Glacier.
The mountain has six ski areas: Timberline, Mount Hood Meadows, Ski Bowl, Cooper Spur, Snow Bunny, and Summit. They total over 4,600 acres or 7.2 square mile s of skiable terrain; Timberline offers the only year-round lift-served skiing in North America.
Mount Hood is part of the Mount Hood National Forest, which has 1.067 million acres (1667 square miles), four designated wilderness areas which total 189,200 acres (295.6 square miles) and more than 1,200 miles of hiking trails.
The glacially eroded summit area consists of several andesitic or dacitic lava domes; Pleistocene collapses produced avalanches and rapidly moving mudflows called lahars that traveled across the Columbia River to the north. The eroded volcano has had at least four major eruptive periods during the past 15,000 years.
The last three eruptions at Mount Hood occurred within the past 1,800 years from vents high on the southwest flank and produced deposits that were distributed primarily to the south and west along the Sandy and Zigzag Rivers. The last eruptive period took place around 170 to 220 years ago, when dacitic lava domes, pyroclastic flows and mudflows were produced without major explosive eruptions. The prominent Crater Rock just below the summit is hypothesized to be the remains of one of these now-eroded domes. This period includes the last major eruption of 1781-82 with a slightly more recent episode ending shortly before the arrival of Lewis and Clark in 1805. The latest minor eruptive event occurred in August 1907.
The glaciers on the mountain's upper slopes may be a source of potentially dangerous lahars when the mountain next erupts. There are vents near the summit that are known for emitting noxious gases such as carbon dioxide and sulfur dioxide. Prior to the 1980 eruption of Mount St. Helens, the only known fatality related to volcanic activity in the Cascades occurred in 1934 when a climber suffocated in oxygen-poor air while exploring ice caves melted by fumaroles in Coalman Glacier.
Since 1950, there have been several earthquake swarms each year at Mount Hood, most notably in July 1980 and June 2002. Seismic activity is monitored by the USGS Cascades Volcano Observatory located in Vancouver, Washington, which issues weekly updates, or daily updates when significant eruptive activity is occurring at a Cascades volcano. The most recent evidence of volcanic activity at Mount Hood consists of fumaroles near Crater Rock and hot springs on the flanks of the volcano.
Photograph copyright Jon Burch Photography
March 31st, 2012
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