DESCRIPTION:
Mount Adams Volcano, Washington

Adams87_mount_adams_from_trout_lake_11-05-87.jpg
Mount Adams, Washington, as seen from Trout Lake, Washington.
USGS Photograph taken on November 5, 1987, by Lyn Topinka.
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Location: Washington

Latitude: 46.206 N

Longitude: 121.49 W

Height: 3,742 Meters (12,276 Feet)

Type: Stratovolcano

Number of eruptions in past 200 years: 0

Latest Eruptions: More than 3,500 years ago ² ... No more than 1,000 or 2,000 years ago ³.

Present thermal activity: Fumaroles emitting steam and hydrogen sulfide in the crater area.

Remarks: Debris flows are lastest events ² ... Appears to consist of a group of several superimposed volcanic cones. Summit crater has extensive sulfur deposits that were formerly mined ³.

Mount Adams, one of the largest volcanoes in the Cascade Range, dominates the Mount Adams volcanic field in Skamania, Yakima, Klickitat, and Lewis counties and the Yakima Indian Reservation of south-central Washington. The nearby Indian Heaven and Simcoe Mountains volcanic fields lie west and southeast, respectively, of the 1,250 square kilometers (500 square miles) Adams field. Even though Mount Adams has been less active during the past few thousand years than neighboring Mounts St. Helens, Rainier, and Hood, it assuredly will erupt again. Future eruptions will probably occur more frequently from vents on the summit and upper flanks of Mount Adams than from vents scattered in the volcanic fields beyond. Large landslides and lahars that need not be related to eruptions probably pose the most destructive, far-reaching hazard of Mount Adams.

Mount Adams stands astride the Cascade Crest some 50 kilometers due east of Mount St. Helens. The towering stratovolcano (3,742 meters - 12,276 feet) is marked by a dozen glaciers, most of which are fed radially from its summit icecap. In the High Cascades, Mount Adams is second in eruptive volume only to Mount Shasta, and it far surpasses its loftier neighbor Mount Rainier (which is perched on a pedestal of Miocene granodiorite). Adams's main cone exceeds 200 cubic kilometers, and at least half as much more was eroded during late Pleistocene time form earlier high-standing components of the compound edifice: peripheral basalt adds another 70 cubic kilometers or so.

Fifty kilometers north of the Columbia River, Mount Adams is reached most rapidly from Trout Lake, which is two hours drive from Portland, Oregon, by paved road. U.S. Forest Service roads from Trout Lake, Glenwood, or Randle, Washington, lead toward the volcano.

Northwest Indians told early explorers about the fiery Mount St. Helens. In fact, an Indian name for the mountain, Louwala-Clough, means "smoking mountain". According to one legend, the mountain was once a beautiful maiden, "Loowit". When two sons of the Great Spirit "Sahale" fell in love with her, she could not choose between them. The two braves, Wyeast and Klickitat fought over her, burying villages and forests in the process. Sahale was furious. He smote the three lovers and erected a mighty mountain peak where each fell. Because Loowit was beautiful, her mountain (Mount St. Helens) was a beautiful, symmetrical cone of dazzling white. Wyeast (Mount Hood) lifts his head in pride, but Klickitat (Mount Adams) wept to see the beautiful maiden wrapped in snow, so he bends his head as he gazes on St. Helens.

Native American legends abound with descriptions of the brothers Wy'east (Hood) and Pahto (Adams) battling for the fair La-wa-la-clough (St. Helens).

The Native Americans ... they called the mountain Pahtoe.

Both St. Helens and Hood got their "English" names long before Adams, whose name survives from an 1839 scheme by Hall J. Kelly to make the Cascades the Presidential Range. He was inspired, according to Cheryl, by Lewis and Clark's naming Mount Jefferson in Oregon after the president who supported their journey across the continent. Kelly, however, intended the name Adams to go to Mount Hood -- he left the mountain in Washington out of the plan entirely. And the person who mapped the mountains mixed up Kelly's names and also put the name Mount Adams 40 miles in the wrong direction -- where there happened to be a mountain ready to bear the name. The Native Americans, of course, knew it was there all along -- they called the mountain Pahtoe. "Mount Adams" stuck firmly after 1853, when the Pacific Railroad Expedition put the name on their map. As for the grand Presidential Range scheme -- well, Cheryl said, "very few of the names took."

Mount Adams is composed of lava flows and fragmental rocks of basaltic andesite and andesite; numerous satellitic vents on the flanks of the volcano have erupted rocks ranging from basalt to dacite. Most of the main cone is younger than 220,000 years. Seven postglacial lava flows issued from flank vents, the youngest of which is between 6,850 and 3,500 years old. Debris avalanches and lahars affected several valleys around the volcano during postglacial time; the longest lahar extended at least 52 kilometers from the volcano. A large amount of hydrothermally altered material in this and one other lahar and in one debris avalanche implies they originated as avalanches of wet, altered, clay-rich debris from near the summit. The youngest such event was a debris avalanche that descended the southwest flank in 1921. Numerous debris flows generated by glacial and meteorologic processes occur frequently at Mount Adams, but typically affect areas within only a few kilometers of the volcano. Postglacial eruptions and weak, diffuse fumarolic emissions in the summit area suggest that the volcano is capable of erupting again.

Mount Adams stands astride the Cascade Crest some 50 kilometers due east of Mount St. Helens. The towering stratovolcano is marked by a dozen glaciers, most of which are fed radially from its summit icecap. In the High Cascades, Mount Adams is second in eruptive volume only to Mount Shasta, and it far surpasses its loftier neighbor Mount Rainier (which is perched on a pedestal of Miocene granodiorite). Adams's main cone exceeds 200 cubic kilometers, and at least half as much more was eroded during late Pleistocene time form earlier high-standing components of the compound edifice: peripheral basalt adds another 70 cubic kilometers or so.

Nearly all the high cone above 2,300 meters in elevation was constructed during latest Pleistocene time, probably between 20 and 10 thousand years ago, explaining the abundance of late-glacial till and the scarcity of older till. Products of this eruptive episode range from 54% to 62% SiO2 on the main cone. ...

There have been no recorded eruptions of Mount Adams, and, of the 11 Holocene vents, none is known certainly to have erupted products younger than 3,500 years. Seven of the Holocene eruptions took place at flank vents 2,000-2,500 meters in elevation and produced a wide variety of compositions (49-61% SiO2); the other four vents are peripheral to the main cone at 1,100-1,600 meters and 48-54% SiO2. ...

Weak H2S-bearing fumaroles still rise from crevasses in the summit icecap. Subjected to this solfataric flux, the breccia-and-scoria core of the stratovolcano has suffered severe acid-sulfate leaching and deposition of alunite, kaolinite, silica, gypsum, sulfur, and iron oxides. Where exposed in glacial headwalls, the 4-square-kilometer rotten core is a persistent source of avalanches and debris flows; the longest traveled 40 kilometers after breaking loose approximately 5,000 years ago, creating the southwest notch and shelf for the perched White Salmon Glacier.

During the past one million years, numerous volcanic vents were active throughout south-central Washington, from Vancouver to Goldendale. Most were probably active for relatively short times ranging from days to tens of years. Unlike Mount Adams, which has erupted repeatedly for hundreds of thousands of years, these vents typically did not erupt more than once. Rather, each erupting vent built a separate, small volcano, and over time a field of numerous overlapping volcanoes was created. Clusters of these vents define the Mount Adams, Indian Heaven, and Simcoe Mountains volcanic fields. In addition, the Goat Rocks volcanic center lies 30 kilometers (18 miles) north of Mount Adams. The Mount Adams and Indian Heaven fields have been the most active recently; the Simcoe field and the Goat Rocks center have not erupted for hundreds of thousands of years. Because the numerous volcanoes in these fields were active for geologically brief times, they are much smaller than Mount Adams. Underwood Mountain, which lies west of the mouth of the White Salmon River, is one such volcano. It is about 8 kilometers (5 miles) in diameter and less than 800 meters (2,600 feet) high. About 9,000 years ago, the Big Lava Bed issued from a small volcano less than 300 meters (1,000 feet) high and partly filled the northwest part of the Little White Salmon River drainage basin with a thick lava flow almost 16 kilometers (10 miles) long. A few ancient lava flows were sufficiently large to flow down tributary valleys, spread out on the floor of the Columbia River Gorge, and dam the river to form a lake. The river then cut a new channel around or through the lava flow.

The Indian Heaven volcanic field is midway between Mount St. Helens and Mount Adams; its principal feature is a 30 kilometer long N10^o E-trending linear zone of coalescing, polygenetic shield volcanoes, cinder cones, and flows with a volume of 100 cubic kilometers. The shield volcanoes, which form the backbone of the volcanic field, are from north to south: ...

Basalt to mafic andesite lava flows range from 0.4 to 24 meters in thickness, whereas andesite flows are up to 90 meters thick. Individual flows extend up to 46 kilometers in length, have areas to 116 square kilometers, and volumes to 1.2 cubic kilomters. Most flow less than 150 thousand years old contain extensive lava tubes, making the Indian Heaven Volcanic Field an important speleological area.

Lava flow units are separated stratigraphically into two main groups. The older group has been extensively eroded during the Hayden Creek Glaciation, around 250 to 150 thousand years ago. A younger group ranges in age between Hayden Creek Glaciation and Evans Creek Glaciation (around 25 to 15 thousand years ago). The youngest unit is Big Lava Bed, dated by radiocarbon at 8,150 years BP (uncorrected). The oldest lavas are believed to be greater than 0.73 million years due to their relative freshness and normal magnetic polarity. If the entire field formed since 0.73 million years the average eruption rate would be 375 cubic meters per day. If the last eruption was Big Lava Bed (volume 0.88 cubic kilometers) the field is overdue for another eruption.

Mount Adams is a large stratovolcano in southwestern Washington State about 50 kilometers north of the Columbia River and 50 kilometers east of Mount St. Helens. The glacier-covered cone of andesitic lava and breccia towers 2,500 meters above the surround Cascade Range. The present cone was formed before the last major glaciation, which occurred between 25,000 and 12,000 years ago (Porter and others, 1983). The lowermost lava flows exposed in the main cone have an age of about 460,000 years B.P. (before present) and overlap the eroded remnants, which range in age from 460,000 to 520,000 years B.P., of an older andesitic center called the Hellroaring volcano (Hildreth and Lanphere, 1994).

At least five lahars and a debris avalanche, originating at Mount Adams, moved into the White Salmon River drainage basin during the past 12,000 years. The deposits produced by these lahars range in volume from 4 to 66 million cubic meters and they moved as much as 60 kilometers down valley. About 6,000 years ago, the largest of the lahars inundated about 15 square kilometers of the lowland near Trout Lake and dammed a tributary stream to form Trout Lake. About 200 years ago, another lahar filled valleys to depths as much as 50 meters, and produced run-ups of as much as 30 meters on objects in its path, but left only thin veneers on valley sides and floors. Three smaller lahars and the debris avalanche of 1921 extend between 5 and 15 kilometers from Mount Adams.

During the past 10,000 years, the steep upper slopes of Mount Adams have produced several notable debris avalanches. In 1921, about 4 million cubic meters (5 million cubic yards) of altered rock fell from the head of Avalanche Glacier on the southwest flank of the volcano and traveled almost 6 kilometers (4 miles) down Salt Creek valley. The debris avalanche contained or acquired sufficient water to partly transform into small lahars.

Ancient debris avalanches of much larger size have also occurred at Mount Adams, and these formed lahars that traveled far down the White Salmon and other valleys. An avalanche of roughly 70 million cubic meters (90 million cubic yards) of debris initiated the largest of these lahars about 6000 years ago. This lahar inundated the Trout Lake lowland and continued down the valley of the White Salmon River at least as far as Husum, more than 55 kilometers (35 miles) from Mount Adams. The lahar deposit left in the lowland varies from 1 to 20 meters (3 to 65 feet) thick; it is clearly visible today as a sediment layer in the banks of the White Salmon River and as isolated blocks (some more than 5 meters (16 feet) in diameter) that protrude from fields and meadows.

Seven postglacial lava flows issued from flank vents (of Mount Adams), the youngest of which is between 6850 and 3500 years old. Debris avalanches and lahars affected several valleys around the volcano during postglacial time; the longest lahar extended at least 52 kilometers (32 miles) from the volcano. A large amount of hydrothermally altered material in this and one other lahar and in one debris avalanche implies they originated as avalanches of wet, altered, clay-rich debris from near the summit. The youngest such event was a debris avalanche that descended the southwest flank in 1921. Numerous debris flows generated by glacial and meteorologic processes occur frequently at Mount Adams, but typically affect areas within only a few kilometers of the volcano.

Mount Adams Debris Avalanche Menu

Between 1931 and 1935, Mr. Wade Dean's "Glacier Mining Company" mined solfatara deposits for sulfur in the gently sloping area north of the summit of Mount Adams. The summit crater is the center of the most intensive alteration; primary sulfur deposits occur there with gypsum, alum and silica.

General Information about Volcanoes and Mining and Mineral Resources

The White Salmon and Avalanche Glaciers, which cut deeply into the southwest flank of Mount Adams, form the headwaters of the White Salmon River, a southerly flowing tributary of the Columbia River. On other sides of Mount Adams the Lewis, Cispus, and Klickitat Rivers drain radially west, northwest, and southeast.

The White Salmon River catchment here is divided into four reaches:

At least five lahars and a debris avalanche, originating at Mount Adams, moved into the White Salmon River drainage basin during the past 12,000 years. The deposits produced by these lahars range in volume from 4 to 66 million cubic meters and they moved as much as 60 kilometers down valley. About 6,000 years ago, the largest of the lahars inundated about 15 square kilometers of the lowland near Trout Lake and dammed a tributary stream to form Trout Lake.

During the past one million years, numerous volcanic vents were active throughout south-central Washington, from Vancouver to Goldendale. Most were probably active for relatively short times ranging from days to tens of years. Unlike Mount Adams, which has erupted repeatedly for hundreds of thousands of years, these vents typically did not erupt more than once. Rather, each erupting vent built a separate, small volcano, and over time a field of numerous overlapping volcanoes was created. Clusters of these vents define the Mount Adams, Indian Heaven, and Simcoe Mountains volcanic fields. In addition, the Goat Rocks volcanic center lies 30 kilometers (18 miles) north of Mount Adams. The Mount Adams and Indian Heaven fields have been the most active recently; the Simcoe field and the Goat Rocks center have not erupted for hundreds of thousands of years.

Because the numerous volcanoes in these fields were active for geologically brief times, they are much smaller than Mount Adams. Underwood Mountain, which lies west of the mouth of the White Salmon River, is one such volcano. It is about 8 kilometers (5 miles) in diameter and less than 800 meters (2,600 feet) high. About 9,000 years ago, the Big Lava Bed issued from a small volcano less than 300 meters (1,000 feet) high and partly filled the northwest part of the Little White Salmon River drainage basin with a thick lava flow almost 16 kilometers (10 miles) long. A few ancient lava flows were sufficiently large to flow down tributary valleys, spread out on the floor of the Columbia River Gorge, and dam the river to form a lake. The river then cut a new channel around or through the lava flow.

MORE about Mount Adams Vicinity Volcanic Fields

In addition to locating regional earthquakes, the Pacific Northwest Seismograph Network (PNSN), in cooperation with the Cascades Volcano Observatory, is also responsible for monitoring seismic activity at volcanoes in the Pacific Northwest. The PNSN currently operates seismometers on or near Mount Adams, Mount Rainier, Mount St. Helens, Mount Hood, Mount Baker, Three Sisters, and Crater Lake.

Mount Adams Monitoring Menu

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