Mount Hood

The glacially eroded summit area consists of several andesitic or dacitic lava domes; Pleistocene collapses produced avalanches and lahars (rapidly moving mudflows) that traveled across the Columbia River to the north. The eroded volcano has had at least four major eruptive periods during the past 15,000 years. The last three occurred within the past 1,800 years from vents high on the SW flank and produced deposits that were distributed primarily to the south and west along the Sandy and Zigzag rivers. The last eruptive period took place aro ...

See also:

Mount Hood, Mount Hood - Geology, Mount Hood - Origin of its name

Read more here: » Mount Hood: Encyclopedia II - Mount Hood - Geology

For more detail, see Mount Mazama. The caldera was created in a massive volcanic eruption that lead to the subsidence of Mount Mazama around 4860 BC. Since that time, all eruptions on Mazama have been confined to the caldera. Lava eruptions later created a central platform, Wizard Island, Merriam Cone, and other, smaller volcanic features, including a rhyodacite dome that was eventually created atop the central platform. Sediments and landslide ...

See also:

Crater Lake, Crater Lake - Geology

Read more here: » Crater Lake: Encyclopedia II - Crater Lake - Geology

Crater Lake is a lake in the U.S. state of Oregon that is 5 by 6 miles (8 by 9.6 km) and 1958 ft (597 m) deep. It is Crater Lake National Park's most prominent feature and is famous for its deep blue color, water clarity and vertical driftwood, named Old Man of the Lake. The lake partly fills a nearly 4000 ft (1220 m) deep caldera that was formed around 6900 years ago by the collapse of the volcano Mount Mazama. The lake's average depth is around 1500 ft (450 m). Its deepest point has been measured at 1932 ft (589 m) dee ...

Including:

• Crater Lake - Geology

Read more here: » Crater Lake: Encyclopedia - Crater Lake

Several small earthquakes beginning as early as March 16, 1980, indicated that magma may have been moving below the volcano. Then on March 20 at 3:47 PM Pacific Standard Time (all times will be in PST), a shallow Richter magnitude 4.2 earthquake, centered below the mountain's north flank, definitely signaled the volcano's violent return from 123 years of hibernation. A gradually building earthquake swarm saturated area seismographs and started to climax at about noon on March 25, reaching peak levels in the next two days (a to ...

See also:

1980 eruption of Mount St. Helens, 1980 eruption of Mount St. Helens - Buildup to disaster, 1980 eruption of Mount St. Helens - North face slides away, 1980 eruption of Mount St. Helens - Pyroclastic flows, 1980 eruption of Mount St. Helens - Initial lateral blast, 1980 eruption of Mount St. Helens - Lateral blast result, 1980 eruption of Mount St. Helens - Later flows, 1980 eruption of Mount St. Helens - Ash column grows, 1980 eruption of Mount St. Helens - Mudslides flow downstream, 1980 eruption of Mount St. Helens - Aftermath, 1980 eruption of Mount St. Helens - Direct results, 1980 eruption of Mount St. Helens - Digging out, 1980 eruption of Mount St. Helens - Cost, 1980 eruption of Mount St. Helens - Later eruptions

Read more here: » 1980 eruption of Mount St. Helens: Encyclopedia II - 1980 eruption of Mount St. Helens - Buildup to disaster

According to geological evidence, St. Helens started growth in the Pleistocene 37,600 years ago with dacite and andesite eruptions of pumice and ash. 36,000 years ago a large mudflow cascaded down the volcano (mudflows were very significant forces in all of St. Helens' eruptive cycles). Parts of this ancestral cone were fragmented and transported by glaciers 14,000 to 18,000 years ago during the last ice age. Mt. St. Helens is known to have erupted in four major stages, the present having begun around 2500 BC after 6000 years of dormancy. Th ...

See also:

Mount St. Helens, Mount St. Helens - Geographic setting and description, Mount St. Helens - Human history, Mount St. Helens - Geologic history, Mount St. Helens - Smith Creek and Pine Creek Eruptive Periods, Mount St. Helens - Castle Creek and Sugar Bowl Eruptive Periods, Mount St. Helens - Kalama and Goat Rocks Eruptive Periods, Mount St. Helens - The 1980 eruption, Mount St. Helens - Post-1980 activity, Mount St. Helens - October 1 2004-present eruption

Read more here: » Mount St. Helens: Encyclopedia II - Mount St. Helens - Geologic history

Glacier Peak is actually a small stratovolcano despite its elevation of 10,541 feet (3213 meters); it is perched atop a ridge and the volcanic part is no higher than 500-1000 meters above the ridge. Glacier Peak and Mount St. Helens are the only volcanoes in Washington that have generated large, explosive eruptions in the past 15,000 years. Their violent behavior results from the type of molten rock (magma) they produce. Dacite, the typical magma type of Mount St. Helens and Glacier Peak, is too viscous to flow easily out of the erupt ...

See also:

Glacier Peak, Glacier Peak - Eruptive history, Glacier Peak - External link

Read more here: » Glacier Peak: Encyclopedia II - Glacier Peak - Eruptive history

The mountain grew in three phases. Garabldi's first phase resulted in the creation of a broad composite cone made of dacite and breccia that has been potassium-argon dated to 250,000 years old. Parts of this ancestral volcano are exposed on Garibaldi's lower northern and eastern flanks and on the upper 800 feet (240 m) of Brohm Ridge. Around where Columnar Peak and possibly Glacier Pikes are now located, a series of coalescing dacite domes were constructed. During the ensuing long period of dormancy, the Cheekye River cut a deep valley into the cone's western ...

See also:

Mount Garibaldi, Mount Garibaldi - Geology, Mount Garibaldi - Garibaldi Lake Volcanic Field

Read more here: » Mount Garibaldi: Encyclopedia II - Mount Garibaldi - Geology

Native Americans in the area have created a detailed legend concerning the three smoking mountains that guard the Columbia River. According to their Bridge of the Gods tale, Wyeast (Mount Hood) and Pahto (Mount Adams; also called Paddo or Klickitat by natives) were the sons of Great Spirit. The brothers both competed for the love of the beautiful La-wa-la-clough (Mount St. Helens). When La-wa-la-clough chose Pahto, Wyeast struck his brother so hard that Pahto's head was flattened and Wyeast took La-wa-la-clough from him (thus attempting to e ...

See also:

Mount Adams Washington, Mount Adams Washington - History, Mount Adams Washington - Glaciers, Mount Adams Washington - Geology, Mount Adams Washington - Summit area, Mount Adams Washington - Area around Adams, Mount Adams Washington - Reference, Mount Adams Washington - External link

Read more here: » Mount Adams Washington: Encyclopedia II - Mount Adams Washington - History

Mount Bachelor was born between 11,000-15,000 years ago as a shield volcano, but was later capped with a stratovolcano as the eruptions apparently became more explosive over time. It is the youngest prominent volcano in the Three Sisters area of Oregon. Bachelor is composed mainly of basalt and basaltic andesite. It last erupted between 8,000 and 10,000 years ago, and is entirely covered with Mazama ash from the catastrophic eruption of Mount Mazama about 6,845 years ago. There is no geothermal activity at present, although the volcano itself pr ...

See also:

Mount Bachelor, Mount Bachelor - Geology, Mount Bachelor - Skiing

Read more here: » Mount Bachelor: Encyclopedia II - Mount Bachelor - Geology

Mount St. Helens - Formative years. According to geological evidence, St. Helens started growth in the Pleistocene 37,600 years ago with dacite and andesite eruptions of pumice and ash. 36,000 years ago a large mudflow cascaded down the volcano (mudflows were very significant forces in all of St. Helens' eruptive cycles). Parts of this ancestral cone were fragmented and transported by glaciers 14,000 to 18,000 years ago during the last ice age. Mt. St. Helens is known to have erupted in four major stages, the pre ...

See also:

Mount St. Helens, Mount St. Helens - Geographic setting and description, Mount St. Helens - Human history, Mount St. Helens - Geologic history, Mount St. Helens - Formative years, Mount St. Helens - Smith Creek and Pine Creek Eruptive Periods, Mount St. Helens - Castle Creek and Sugar Bowl Eruptive Periods, Mount St. Helens - Kalama and Goat Rocks Eruptive Periods, Mount St. Helens - The 1980 eruption, Mount St. Helens - Post-1980 activity, Mount St. Helens - October 1 2004-present eruption

Read more here: » Mount St. Helens: Encyclopedia II - Mount St. Helens - Geologic history

Main article: Geology of Mount Shasta The mountain consists of four separate cones buried atop one another. Shastina 12,300 ft (3,749 m) is the most obvious cone and forms a lesser summit. It has a fully intact summit crater which shows that Shastina postdates the last ice age. The rest of Shasta's surface is relatively free of glacial erosion except, paradoxically, for its south side where Sargents Ridge runs parallel to the U-shaped Avalanche Gulch (the largest glacial valley on the volcano, although it does not presently have a glacier in it). There are five named, yet tiny, glaciers ...

See also:

Mount Shasta, Mount Shasta - Geology, Mount Shasta - Volcanic hazards, Mount Shasta - Religion, Mount Shasta - Cultural References

Read more here: » Mount Shasta: Encyclopedia II - Mount Shasta - Geology

Isolated ridges of lava and hydrothermally altered rock, especially in the area of Sherman Crater, are exposed between glaciers on the upper flanks of the volcano: the lower flanks are steep and heavily vegetated. The volcano rests on a foundation of non-volcanic rocks in a region that is largely non-volcanic in origin. The present-day cone is relatively young, perhaps less than 30,000 years old, but it sits atop a similar older volcanic cone called Black Buttes volcano which was active between 500,000 and 300,000 years ago. Much of M ...

See also:

Mount Baker, Mount Baker - Geology, Mount Baker - Recreation

Read more here: » Mount Baker: Encyclopedia II - Mount Baker - Geology

Mount Rainier's earliest lavas are over 840,000 years old and are part of the Lily Formation.(2.9 million to 840,000 years ago) The early lavas formed a "proto-Rainier" or an ancestral cone prior to the present-day cone. The present cone is over 500,000 years old (Sisson 1995). The volcano is highly eroded, with glaciers on its slopes, and appears to be made mostly of andesite. Rainier likely once stood even higher than today before a major debris avalanc ...

See also:

Mount Rainier, Mount Rainier - Geological history, Mount Rainier - Human history

Read more here: » Mount Rainier: Encyclopedia II - Mount Rainier - Geological history

Before the arrival of white settlers, the areas surrounding Lassen Peak, especially in the east and south, were the traditional home of the (Northeastern) Maidu. Lassen Peak was named in honor of Danish blacksmith Peter Lassen who guided immigrants past the peak to Sacramento Valley in the 1830s. Lassen's trail, however, never found general long-term use because it was considered unsafe. Nobles Emigrant Trail, named after William Nobles, which linked Applegate Trail in Nevada to N ...

See also:

Lassen Peak, Lassen Peak - Geology, Lassen Peak - History, Lassen Peak - Reference

Read more here: » Lassen Peak: Encyclopedia II - Lassen Peak - History

Mount St. Helens is 34 miles (55 km) almost due west of Mount Adams, which is in the eastern part of the Cascade Range. These "sister and brother" volcanic mountains are each about 50 miles (80 km) from Mount Rainier, the giant of Cascade volcanoes. Mount Hood, the nearest major volcanic peak in Oregon, is about 60 miles (95 km) southeast of Mount St. Helens. Mount St. Helens is geologically young compared to the other major Cascade volcanoes. It was formed only within the last 40,000 years, and the pre-1980 summit cone started to grow only about 2200 years ago. The volcano is also known to ...

See also:

Mount St. Helens, Mount St. Helens - Geographic setting and description, Mount St. Helens - Human history, Mount St. Helens - Geologic history, Mount St. Helens - Smith Creek and Pine Creek Eruptive Periods, Mount St. Helens - Castle Creek and Sugar Bowl Eruptive Periods, Mount St. Helens - Kalama and Goat Rocks Eruptive Periods, Mount St. Helens - The 1980 eruption, Mount St. Helens - Post-1980 activity, Mount St. Helens - October 1 2004-present eruption

Read more here: » Mount St. Helens: Encyclopedia II - Mount St. Helens - Geographic setting and description

An unusual volcanic structure called The Table is located 3.5 miles (~5.5 km) north of Garibaldi. This several hundred foot high flat-topped volcano is made of layers of andesitic dacite that are arranged like a stack of more or less equal sized pancakes. The Table was formed in the late Pleistocene at a time when the Cordilleran ice sheet covered the region. As the volcano's lava rose it melted the part of the ice sheet above The Table's vent, creating space for the lava to move into. Repeated ...

See also:

Mount Garibaldi, Mount Garibaldi - Geology, Mount Garibaldi - Garibaldi Lake Volcanic Field

Read more here: » Mount Garibaldi: Encyclopedia II - Mount Garibaldi - Garibaldi Lake Volcanic Field

The first recorded sighting of Mount St. Helens by Europeans was by Royal Navy Commander George Vancouver and the officers of HMS Discovery on May 19, 1792, while they were surveying the northern Pacific Ocean coast from 1792 to 1794. Vancouver named the mountain for British diplomat Alleyne Fitzherbert, Baron St. Helens on October 20, 1792, as it came into view when the Discovery passed into the mouth of the Columbia River. Years later, the mountain was visited by its first major eruption after explorers, traders, and m ...

See also:

Mount St. Helens, Mount St. Helens - Geographic setting and description, Mount St. Helens - Human history, Mount St. Helens - Geologic history, Mount St. Helens - Smith Creek and Pine Creek Eruptive Periods, Mount St. Helens - Castle Creek and Sugar Bowl Eruptive Periods, Mount St. Helens - Kalama and Goat Rocks Eruptive Periods, Mount St. Helens - The 1980 eruption, Mount St. Helens - Post-1980 activity, Mount St. Helens - October 1 2004-present eruption

Read more here: » Mount St. Helens: Encyclopedia II - Mount St. Helens - Human history

On October 1, 2004, Mount St. Helens sent steam and ash into the air for approximately 25 minutes, yielding evacuation orders from nearby areas. Mount St. Helens vented steam, ash and rock once more into the air. On October 6, 2004, the U.S. Geological Survey announced that the alert level was being lowered, saying "We no longer think that an eruption is imminent in the sense of minutes or hours." Magma reached the surface of the volcano around October 11, 2004, resulting in the building of a new lava dome on the existing dome' ...

See also:

Mount St. Helens, Mount St. Helens - Geographic setting and description, Mount St. Helens - Human history, Mount St. Helens - Geologic history, Mount St. Helens - Smith Creek and Pine Creek Eruptive Periods, Mount St. Helens - Castle Creek and Sugar Bowl Eruptive Periods, Mount St. Helens - Kalama and Goat Rocks Eruptive Periods, Mount St. Helens - The 1980 eruption, Mount St. Helens - Post-1980 activity, Mount St. Helens - October 1 2004-present eruption

Read more here: » Mount St. Helens: Encyclopedia II - Mount St. Helens - October 1 2004-present eruption

The Cascade Range is a mountainous region famous for its chain of tall volcanoes called the High Cascades that run north-south along the west coast of North America from British Columbia to the Shasta Cascade area of northern California. The small part of the range in British Columbia is called the Cascade Mountains or Canadian Cascades. The Cascades are part of the Pacific Ring of Fire, the ring of volcanoes around the Pacific Ocean. All of the known historic eruptions in the contiguous United States have ...

Including:

• Cascade Range - History
• Cascade Range - Geography
• Cascade Range - Human uses
• Cascade Range - High Cascades
• Cascade Range - Protected areas
• Cascade Range - National parks
• Cascade Range - National monuments
• Cascade Range - Provincial Parks

Read more here: » Cascade Range: Encyclopedia - Cascade Range

In Scientology doctrine, Xenu (also Xemu) is a galactic ruler (of the "Galactic Confederacy") who, 75 million years ago, brought billions of people to Earth, stacked them around volcanoes and blew them up with hydrogen bombs. Their souls then clustered together and stuck to the bodies of the living, and continue to cause problems today. These events are known to Scientologists as "Incident II", and the traumatic memories associated with them as The Wall of Fire or the R6 implant. The story of Xenu is ...

Including:

• Xenu - Summary of the Xenu story
• Xenu - Xenu's volcanoes
• Xenu - Xenu in Scientology doctrine
• Xenu - Origins of the Xenu story
• Xenu - Other versions of the Xenu story
• Xenu - Xenu in popular culture
• Xenu - The influence of OT III on Scientology
• Xenu - Xenu or Xemu?
• Xenu - The Church of Scientology's position on Xenu
• Xenu - Scientific critiques
• Xenu - Sources

Read more here: » Xenu: Encyclopedia - Xenu