Goat Rocks
Encyclopedia
The Goat Rocks are a series of rugged volcanic peaks in the Cascade Range
, roughly between Mount Rainier
and Mount Adams
in southern Washington state. They are named after the numerous mountain goat
s which live in the area, and are at the core of the eponymous Goat Rocks Wilderness
.
, a large stratovolcano. It is located in a zone of intermittent volcanism which has produced many small vents. Over time, overlap occurred, and the vents now make up the Mount Adams volcanic field, Indian Heaven, and even parts of Goat Rocks.
The peaks are the eroded remnants of a stratovolcano
, termed the Goat Rocks volcano, which about 2 million years ago might have been similar to the current large stratovolcanoes in the Cascade Volcanic Arc
, reaching over 10000 feet (3,048 m) high. Once the volcanic eruptions came to an end, the ongoing forces of glacial
erosion
stripped away the outer layers of volcanic ash
deposits and lava flows, uncovering the rocky lava spine
s where magma
had cooled and hardened within the conduits of the volcano. The current eroded volcano has numerous summits reaching about 8000 ft (2,438.4 m).
The Goat Rocks area is notable for its extensive glaciers, despite the modest elevation and southerly location relative to the rest of the Washington Cascades. Five glaciers mantle the north and northeast slopes of the peaks, along with numerous smaller permanent snowfields. The highest point on the Pacific Crest Trail
in Washington is at 7,200 ft (2,200 m) on the northwest flank of Old Snowy Mountain, where the trail crosses the edge of the Packwood Glacier.
The remnant core of the Goat Rocks Volcano is Egg Butte, located north of Old Snowy Mountain in the valley carved by the ice age
Packwood Glacier. Similar to the lava spine
s remaining on the ridges to the south and east of Old Snowy Mountain, the dense core became exposed after the Packwood Glacier removed the softer ash and broken flows around it.
At the base of the valley lies Packwood Lake, formed behind the terminal moraine
created by the [ice age] Packwood Glacier, evidence of the large amount of volcanic material stripped away by the glacier.
Cascade Range
The Cascade Range is a major mountain range of western North America, extending from southern British Columbia through Washington and Oregon to Northern California. It includes both non-volcanic mountains, such as the North Cascades, and the notable volcanoes known as the High Cascades...
, roughly between Mount Rainier
Mount Rainier
Mount Rainier is a massive stratovolcano located southeast of Seattle in the state of Washington, United States. It is the most topographically prominent mountain in the contiguous United States and the Cascade Volcanic Arc, with a summit elevation of . Mt. Rainier is considered one of the most...
and Mount Adams
Mount Adams (Washington)
Mount Adams is a potentially activestratovolcano in the Cascade Range and the second-highest mountain in the U.S. state of Washington.Adams is a member of the Cascade Volcanic Arc, and is one of the arc's largest volcanoes,...
in southern Washington state. They are named after the numerous mountain goat
Mountain goat
The Mountain Goat , also known as the Rocky Mountain Goat, is a large-hoofed mammal found only in North America. Despite its vernacular name, it is not a member of Capra, the genus of true goats...
s which live in the area, and are at the core of the eponymous Goat Rocks Wilderness
Goat Rocks Wilderness
Goat Rocks Wilderness is a U.S. Wilderness Area in Washington, United States. Consisting of portions of Mount Baker-Snoqualmie National Forest and Gifford Pinchot National Forest on the crest of the Cascade Range south of U.S...
.
Geography and geology
The complex is located 18 miles (29 km) north of Mount AdamsMount Adams (Washington)
Mount Adams is a potentially activestratovolcano in the Cascade Range and the second-highest mountain in the U.S. state of Washington.Adams is a member of the Cascade Volcanic Arc, and is one of the arc's largest volcanoes,...
, a large stratovolcano. It is located in a zone of intermittent volcanism which has produced many small vents. Over time, overlap occurred, and the vents now make up the Mount Adams volcanic field, Indian Heaven, and even parts of Goat Rocks.
The peaks are the eroded remnants of a stratovolcano
Stratovolcano
A stratovolcano, also known as a composite volcano, is a tall, conical volcano built up by many layers of hardened lava, tephra, pumice, and volcanic ash. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile and periodic, explosive eruptions...
, termed the Goat Rocks volcano, which about 2 million years ago might have been similar to the current large stratovolcanoes in the Cascade Volcanic Arc
Cascade Volcanoes
The Cascade Volcanoes are a number of volcanoes in a volcanic arc in western North America, extending from southwestern British Columbia through Washington and Oregon to Northern California, a distance of well over 700 mi ...
, reaching over 10000 feet (3,048 m) high. Once the volcanic eruptions came to an end, the ongoing forces of glacial
Glacier
A glacier is a large persistent body of ice that forms where the accumulation of snow exceeds its ablation over many years, often centuries. At least 0.1 km² in area and 50 m thick, but often much larger, a glacier slowly deforms and flows due to stresses induced by its weight...
erosion
Erosion
Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...
stripped away the outer layers of volcanic ash
Volcanic ash
Volcanic ash consists of small tephra, which are bits of pulverized rock and glass created by volcanic eruptions, less than in diameter. There are three mechanisms of volcanic ash formation: gas release under decompression causing magmatic eruptions; thermal contraction from chilling on contact...
deposits and lava flows, uncovering the rocky lava spine
Lava spine
A lava spine is a vertically growing monolith of viscous lava that is slowly forced from a volcanic vent, such as those growing on a lava dome . It may also be considered a kind of dome called a spiny dome . In February of 1983, the dome activity of Mount St...
s where magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...
had cooled and hardened within the conduits of the volcano. The current eroded volcano has numerous summits reaching about 8000 ft (2,438.4 m).
The Goat Rocks area is notable for its extensive glaciers, despite the modest elevation and southerly location relative to the rest of the Washington Cascades. Five glaciers mantle the north and northeast slopes of the peaks, along with numerous smaller permanent snowfields. The highest point on the Pacific Crest Trail
Pacific Crest Trail
The Pacific Crest Trail is a long-distance mountain hiking and equestrian trail on the Western Seaboard of the United States. The southern terminus is at the California border with Mexico...
in Washington is at 7,200 ft (2,200 m) on the northwest flank of Old Snowy Mountain, where the trail crosses the edge of the Packwood Glacier.
The remnant core of the Goat Rocks Volcano is Egg Butte, located north of Old Snowy Mountain in the valley carved by the ice age
Ice age
An ice age or, more precisely, glacial age, is a generic geological period of long-term reduction in the temperature of the Earth's surface and atmosphere, resulting in the presence or expansion of continental ice sheets, polar ice sheets and alpine glaciers...
Packwood Glacier. Similar to the lava spine
Lava spine
A lava spine is a vertically growing monolith of viscous lava that is slowly forced from a volcanic vent, such as those growing on a lava dome . It may also be considered a kind of dome called a spiny dome . In February of 1983, the dome activity of Mount St...
s remaining on the ridges to the south and east of Old Snowy Mountain, the dense core became exposed after the Packwood Glacier removed the softer ash and broken flows around it.
At the base of the valley lies Packwood Lake, formed behind the terminal moraine
Terminal moraine
A terminal moraine, also called end moraine, is a moraine that forms at the end of the glacier called the snout.Terminal moraines mark the maximum advance of the glacier. An end moraine is at the present boundary of the glacier....
created by the [ice age] Packwood Glacier, evidence of the large amount of volcanic material stripped away by the glacier.
List of major peaks
- Gilbert Peak (Mount Curtis Gilbert) 8184 ft (2,494 m)
- Old Snowy Mountain 7930 ft (2,417 m)
- Ives Peak 7840 ft (2,390 m)
- Tieton Peak 7768 ft (2,368 m)
- Johnson Peak 7487 ft (2,282 m)
- Bear Creek Mountain 7336 ft (2,236 m)
- Hogback Mountain 6789 ft (2,069 m)
List of glaciers
- Conrad GlacierConrad GlacierThe Conrad Glacier is a small glacier located in the Goat Rocks region of Washington. Lying on the shaded north side of the Gilbert Peak, the glacier flows north-northeast from an elevation of to a lake at , where the glacier terminates....
- McCall Glacier
- Meade GlacierMeade GlacierThe Meade Glacier is a small, east-facing glacier located in the Goat Rocks region in Washington. The glacier lies to the south of the Gilbert Peak and it ranges in elevation from over down to about . The Conrad Glacier is located to the north this glacier....
- Packwood GlacierPackwood GlacierThe Packwood Glacier is a small, northwest-facing glacier located in the Goat Rocks region of Washington. The glacier lies to the north of the Old Snowy Mountain and averages about in elevation. The much larger McCall Glacier is located to the east....
- Tieton Glacier