Wikipedia: Goat Rocks

Goat Rocks is an extinct stratovolcano in the Cascade Range, located between Mount Rainier and Mount Adams in southern Washington, in the United States. Part of the Cascade Volcanoes, it was formed by the subduction of the Juan de Fuca Plate under the western edge of the North American Plate. The volcano was active from 3.2 million years ago until eruptions ceased between 1 and 0.5 million years ago. Throughout its complex eruptive history, volcanism shifted from silicic explosive eruptions to voluminous, mafic activity.

The volcano and the surrounding Goat Rocks Wilderness, established in 1964, are named after the numerous mountain goats which live in the area. The variable climate of the wilderness area supports a host of wildlife, including marmots, pikas, deer, and elk. Various peaks within the wilderness can be climbed or scrambled, and other activities such as hiking are permitted. The area is rife with minerals and resources, including coal, cobalt, copper, and base metals.

Eruptive history

Goat Rocks is a stratovolcano with a somewhat complicated eruptive history. It first became active approximately 3.2 million years ago during the Pliocene epoch, undergoing explosive eruptions^[18] that ejected silicic lava with highly felsic rocks like rhyolite. One of these events produced 650 m (2,133 ft) of tuff that remains, exposed, on the east flank of the existing mountain. Three million years ago Goat Rocks shifted to mafic volcanism, erupting olivine and basalt. As eruptions continued into the Pleistocene epoch, the lava flows became increasingly andesitic, containing mostly pyroxene with phenocrysts as well as hornblende minerals. These andesitic flows formed the volcano's major edifice between roughly 2.5 and 0.5 million years ago,^[3] which may have resembled contemporary Mount Rainier.^[29] At this point in time, Goat Rocks's eruptions had very high volumes and extended far from the volcano,^[3] possibly because multiple satellite vents contributed to eruptions.^[9] Approximately 1 million years ago, Goat Rocks generated an andesitic lava flow extending 80 km (50 mi) down the Naches and Tieton Rivers, which has been recognized as the longest andesite flow on Earth.^[3] Many of the flows immediately surrounding the volcano have since been cut by intrusive dikes, which form a radial arrangement around the volcano's core. As erosion occurred on a large scale, the volcano remained active, producing more hornblende andesite lava flows. Eruptive activity continued at Old Snowy Mountain into the middle to late Pleistocene, yielding hornblende andesite lava flows that were subsequently glaciated in the Cispus River valley; whether Old Snowy Mountain is a vent of Goat Rocks or an independent volcano remains unclear.^[2] Hornblende andesite can also be found on top of the highest point in Goat Rocks, Gilbert Peak.^[2]

Hogback Mountain, a shield volcano north of Goat Rocks and south of White Pass, was identified by Siebert et al. (2010) as a satellite vent of Goat Rocks.^[30] Rising 700 m (2,297 ft) in elevation, it erupted more than 200 m (656 ft) of olivine basalt and basaltic andesite from the end of the Pliocene through the early Pleistocene.^[2] Eruptions from Goat Rocks formed a spread-out volcanic field populated by small lava domes to the north, with dimensions of 29.9 km (19 mi) by 15 km (9 mi).^[15]

Goat Rocks is now classified as an extinct volcano, as its most recent eruptive activity was during the Pleistocene.^[14]

Wilderness

Main article: Goat Rocks Wilderness

Land surrounding Goat Rocks was first protected by the United States Department of Agriculture in February 1931, when approximately 18,009 hectares (44,501 acres) was set aside for preservation. In 1935, this was increased to 29,315 hectares (72,439 acres) of land, then to 33,459 hectares (82,679 acres) in 1940. In 1964, the United States Congress created the Goats Rock Wilderness as part of the National Wilderness Preservation System, delegating its management to the United States Forest Service. Since additional land was incorporated in 1984,^[31] it now encompasses 43,745 hectares (108,096 acres) between Mount Rainier and Mount Adams, straddling the Gifford Pinchot and Okanogan-Wenatchee national forests.^[32] It is bordered by the Yakama Indian Reservation to the southeast.^[31]

The wilderness ranges from 914 to 2,500 m (2,999 to 8,202 ft) in elevation, featuring alpine tundras with glaciers, small lakes, and ponds, as well as 15 different routes that amount to 193 km (120 mi) of trails. One of these trails constitutes the highest segment of the famous Pacific Crest Trail in Washington,^[33] running for 50 km (31 mi) north–south through the middle of the wilderness area.^[32] Because this route is located at such a high elevation, its hikers may experience violent storms that could be dangerous for unprepared parties.^[34] Much of the wilderness is located above the timberline, offering views of alpine scenery.^[31]

Climate and wildlife

Weather within the Wilderness varies due to the mountains acting as a barrier for both weather and temperature. The Cascade Range mountains prevent wet storms from moving, forcing air to rise and then cool. This cooling air cannot hold as much moisture, causing heavy precipitation (up to 381 cm (150 in) in rainfall annually) on the western flanks of the mountains,^[35] which leads to extensive forestation. Snowfall typically totals more than 8 m (26 ft) annually, amounting to snow still being present as late as July or August. In warmer months, melted snow runs off into lakes, keeping them especially full.^[1] Because the mountains are so tall, storm clouds may get stuck even as the rest of the storm moves onward, leading to snowstorms and freezing temperatures year-round. In extreme conditions, these storm cells might endanger hikers by means of strong winds, fog, snow, and rain that can potentially make hiking nearly impossible. On the eastern sides of the mountains, air warms as it drops, producing Chinook winds, considerably lower precipitation, and less forested landscapes. Because of these conditions, temperatures on the western sides of mountains are steady, whereas temperatures on the eastern flanks fluctuate wildly.^[36]

Goat Rocks obtained its name from a population of mountain goats that can be observed around the mountain.^[31] Other fauna include marmots and pikas at high elevations. Deer and elk can be found below the timberline,^[1] including mule deer, mule deer-black-tailed hybrids, Roosevelt elk, and Rocky Mountain elk that were introduced from Yellowstone National Park in 1913. Black-tailed deer are especially common.^[4]

Climbing and recreation

Old Snowy Mountain and Gilbert Peak, two of Goat Rocks's peaks, are frequented by hikers and mountaineers. Both are considered remote summits, although Old Snowy Mountain is the more accessible of the two.^[37] This, coupled with its easier ascent, makes Old Snowy Mountain the more popular climb. There are several routes up the mountain, which take 5–6 hours, rising 1,097 m (3,599 ft) in elevation. Running for 23 km (14 mi) round-trip, Old Snowy can be scrambled or climbed using glaciers, although a trail exists. From the summit, mountaineers can see Mount St. Helens and Mount Rainier in the distance.^[37] Because this area has a lot of loose talus and rock, an avalanche hazard exists.^[38]

The climb up Gilbert Peak was first completed by Fred G. Plummer in 1899.^[19] It also rises 1,097 m (3,599 ft) in elevation, lasting 6–8 hours and running for 26 km (16 mi) round-trip. Because the routes are longer and more technically challenging due to loose rock, scrambling Gilbert is generally considered more difficult than Old Snowy Mountain. Most climbers opt to mount Gilbert early in the climbing season when snow levels are low.^[38]

Recreational activities permitted by the Forest Service at the Wilderness include day hiking, horse riding, and backpacking.^[1] Because Goat Rocks is part of the National Wilderness Preservation System, motor vehicles and means of transport are prohibited.^[39] These include bicycles, wagons, motorboats, and helicopters. A free permit is required for entry to the wilderness.^[40]

Resources

In terms of mineral resources, the Goat Rocks area can be divided into three segments, each rich with certain minerals. The first two are named Packwood Glacier–McCall Basin and Glacier Basin,^[41] and are located near past volcanic vents. These areas exhibit anomalous levels of cobalt, copper, lead, molybdenum, nickel, and zinc, well-dispersed levels of pyrite, and sporadic concentrations of silver.^[42] Area C corresponds to the Clear Fork of the Cowlitz River and lies along the area of contact between Goat Rocks volcano and older volcanoes to the east.^[43] It is distinct from the other two study areas, featuring anomalous amounts of barium, cobalt, copper, and manganese, as well as smaller quantities of lead, molybdenum, nickel, and zinc. Other minerals found in Area C include barite, boron, cinnabar, mercury, pyrite, and tin in concentrates taken from stream-sediment. The water has high concentrations of chlorine, copper, fluorine, and molybdenum, and altered rocks contain arsenic, lead, manganese, molybdenum, and zinc at especially high levels. The Goat Rocks vicinity seems to offer large base metal deposits. Outside the area studied, coal has been identified at the Packwood and Cowlitz fields, and building stones and gravel are being quarried to the north and west of the volcano. The Goat Rocks area's potential resources for oil and gas remain unidentified.^[42] Because no volcanic activity has occurred during the Holocene (within the past 11,700 years), Goat Rocks has very little potential for geothermal resources.^[44]

Claims to three lode mines and a single coal mine were made within the Goat Rocks Wilderness, but the United States Bureau of Mines has no record of production from any of these claims. Historically, two claims have actually been staked in the area, the Mosquito lode near Walupt Lake in 1934, and later, the Glacier lode near Packwood Glacier in 1939. Neither show evidence of assessment work, and both deposits are now abandoned. Miners may have been drawn to the area by news of lode deposits containing gold, silver, and copper along breccia and shear zones to the north of the wilderness area.^[45]

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