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A hotspot volcano is center. [8] Movements of tectonic plates create volcanoes along the plate boundaries, which erupt and form mountains. A volcanic arc system is a series of volcanoes that form near a subduction zone where the crust of a sinking oceanic plate melts and drags water down with the subducting crust. [9]
In some cases, a lava plateau may be part of a single volcano. An example is the massive Level Mountain shield volcano in northern British Columbia, Canada, which covers an area of 1,800 km 2 (690 sq mi) and a volume of 860 km 3 (210 cu mi). [1]
Mount Galunggung (Indonesian: Gunung Galunggung, formerly spelled Galoen-gong, Sundanese: ᮌᮥᮔᮥᮀ ᮍᮜᮥᮀᮍᮥᮀ) is an active stratovolcano in West Java, Indonesia, around 80 km (50 mi) southeast of the West Java provincial capital, Bandung (or around 20 km (12 mi) to the northwest of the West Java town of Tasikmalaya).
Twelve volcanoes in the arc are over 10,000 feet (3,000 m) in elevation, and the two highest, Mount Rainier and Mount Shasta, exceed 14,000 feet (4,300 m). By volume, the two largest Cascade volcanoes are the broad shields of Medicine Lake Volcano and Newberry Volcano, which are about 145 and 108 cubic miles (600 and 450 km 3) respectively.
Augustine Volcano (Alaska) during its eruptive phase on January 24, 2006. A volcano is commonly defined as a vent or fissure in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface.
The rocks that form the backbone of the Sierra Nevada are mostly granitic rocks that formed during the Mesozoic Era, when non-avian dinosaurs roamed the Earth. At that time, an arc-shaped chain of volcanoes, similar to the present-day Cascade volcanic arc, erupted where the Sierra Nevada now stands.
The valley of the Lostine River in the mountains. Glaciers carved out the valleys during the late Pleistocene, which left a number of moraines. [13] The series of moraines is formed by a series of glacial advances and retreats. Glacial till is also a common feature of the valleys. [14]
The remaining valleys derive all their water from the lower northeastern slopes of the volcano, and as a result are smaller. In addition, there are innumerable gulches of various depths which have not yet reached sea level and began to form flood plains, becoming valleys. Still, some of these are more than 300 m (1,000 ft) in depth. [17]