The Goat Rocks, with Gilbert Peak at upper left
|Elevation||8,184 ft (2,494 m)|
|Location||Lewis / Yakima counties, Washington, U.S.|
|Topo map||USGS Old Snowy Mountain, Walupt Lake|
|Age of rock||3.2 million - 730,000 years|
|Volcanic arc||Cascade Volcanic Arc|
|First ascent||Fred G. Plummer, 1899|
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 goats which live in the area, and are at the core of the eponymous Goat Rocks Wilderness.
Geography and geology
The complex is located 18 miles (29 km) north of Mount Adams, 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 10,000 feet (3,000 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 spines where magma had cooled and hardened within the conduits of the volcano. The current eroded volcano has numerous summits reaching about 8,000 ft (2,400 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 spines 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.
List of major peaks
|Gilbert Peak (Mount Curtis Gilbert)||8,184 ft (2,494 m)|
|Old Snowy Mountain||7,930 ft (2,417 m)|
|Ives Peak||7,840 ft (2,390 m)|
|Tieton Peak||7,768 ft (2,368 m)|
|Johnson Peak||7,487 ft (2,282 m)|
|Bear Creek Mountain||7,336 ft (2,236 m)|
|Hogback Mountain||6,789 ft (2,069 m)|
List of glaciers
- Topinka, Lyn (February 27, 2002). "Description: Volcanic Fields and Centers near Mount Adams, Washington". United States Geological Survey. Retrieved April 24, 2010.
- Wood, Charles A.; Jürgen Kienle, eds. (1990). Volcanoes of North America. Cambridge University Press. ISBN 0-521-43811-X.
- Harris, Stephen L. (2005). Fire Mountains of the West: The Cascade and Mono Lake Volcanoes (3rd ed.). Mountain Press Publishing Company. ISBN 0-87842-511-X.
- Beckey, Fred (2000). Cascade Alpine Guide: Climbing and High Routes; Volume 1: Columbia River to Stevens Pass (3rd ed.). Mountaineers Books. ISBN 0-89886-577-8.
- Mueller, Marge and Ted (1995). A Guide to Washington's South Cascades' Volcanic Landscapes. Mountaineers Books. ISBN 0-89886-445-3.