How mountains form? What are the types of Volcanoes? THX?

Question

How mountains form? What are the types of Volcanoes? THX?

Answer 1

Mountains are formed by volcanoes sure. They are also created when two or more continental plates collide.

Abbreviation thx

Short, for thanks (thank you).

Retrieved from "http://en.wiktionary.org/wiki/thx"?

THX Abbreviation for...Home Theater Entertainment?

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CUT AND PASTED the information below from the following web site;

www.geology.sdsu.edu/how_volcanoes_wor...

They give visual representation of the material described and will make the explanation easier to understand!

VOLCANO TYPES

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GENERIC FEATURES

A volcanic vent is an opening exposed on the earth's surface where volcanic material is emitted. All volcanoes contain a central vent underlying the summit crater of the volcano. The volcano's cone-shaped structure, or edifice, is built by the more-or-less symmetrical accumulation of lava and/or pyroclastic material around this central vent system. The central vent is connected at depth to a magma chamber, which is the main storage area for the eruptive material. Because volcano flanks are inherently unstable, they often contain fractures that descend downward toward the central vent, or toward a shallow-level magma chamber. Such fractures may occasionally tap the magma source and act as conduits for flank eruptions along the sides of the volcanic edifice. These eruptions can generate cone-shaped accumulations of volcanic material, called parasitic cones. Fractures can also act as conduits for escaping volcanic gases, which are released at the surface through vent openings called fumaroles.

Summit Crater



Parasitic Cones



Fumarole

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MAIN VOLCANO TYPES

Although every volcano has a unique eruptive history, most can be grouped into three main types based largely on their eruptive patterns and their general forms. The form and composition of the three main volcano types are summarized here:

VOLCANO

TYPE

VOLCANO

SHAPE

COMPOSITION

ERUPTION

TYPE

SCORIA CONE



Straight sides with steep slopes; large summit crater

Basalt tephra; occasionally andesitic

Strombolian

SHIELD VOLCANO



Very gentle slopes; convex upward

Basalt lava flows

Hawaiian

STRATOVOLCANO



Gentle lower slopes, but steep upper slopes; concave upward; small summit crater

Highly variable; alternating basaltic to rhyolitic lavas and tephra with an overall andesite composition

Plinian

SUBORDINATE VOLCANO TYPES -- Lava and tephra can erupt from vents other than these three main volcano types. A fissure eruption, for example, can generate huge volumes of basalt lava; however, this type of eruption is not associated with the construction of a volcanic edifice around a single central vent system. Although point-source eruptions can generate such features as spatter cones and hornitos, these volcanic edifices are typically small, localized, and/or associated with rootless eruptions (i.e., eruptions above the surface of an active lavaflow, unconnected to an overlying magma chamber) . Vent types related to hydrovolcanic processes generate unique volcanic structures, discussed separately under hydrovolcanic eruptions.

For a description of each of the main volcano types, see:

SCORIA CONES

SHIELD VOLCANOES

STRATOVOLCANOES

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WHEN IS A VOLCANO CONSIDERED ACTIVE, DORMANT, OR EXTINCT?

Classifying a volcano as active, dormant, or extinct is a subjective and inexact exercise. A volcano is generally considered active if it has erupted in historic time. This definition, however, is rather ambiguous, because recorded history varies from thousands of years in Europe and the Middle East, to only a few hundred years in other regions of the world, like the Pacific Northwest of the United States. Scientists generally consider a volcano active if it is currently erupting, or exhibiting unrest through earthquakes, uplift, and/or new gas emissions. The Smithsonian Institution's catalog of active volcanoes, recognizes 539 volcanoes with historic eruptions. In addition, there are 529 volcanoes that have not erupted in historic times, but which exhibit clear evidence of eruption in the past 10,000 years. These latter volcanoes are probably best considered "dormant," since they have the potential to erupt again.

Whether or not inactive volcanoes are considered truly extinct, or just dormant, depends partly on the average repose interval between eruptions. As noted in eruptive variability, explosive eruptions like those at Toba and Yellowstone have repose intervals of hundreds of thousands of years, whereas non-explosive eruptions have very short repose intervals. Thus, the Yellowstone region, which has not experienced an eruption for 70,000 years, can not be considered extinct. In fact, many scientists consider Yellowstone to be active because of high uplift rates, frequent earthquakes, and a very active geothermal system. Many inactive scoria cones, on the other hand, may be viewed as extinct shortly after they erupt, because such volcanoes are typically monogenetic and only erupt once.

Answer 2

second question first; http://vulcan.wr.usgs.gov/Glossary/Volca...

first and second questions;

Nature Gallery (Earth)

Mountains

Ancient fossils of marine animals lie buried in the icy peaks of the Himalayas, the highest mountain system in the world. During the Paleozoic and Mesozoic eras (570 million to 65 million years ago) the rocks that form the Himalayas were being laid down as sediment on the floor of an ancient sea. wpe1C.jpg (13188 bytes)

Today, more than 30 Himalayan peaks rise to heights of 7,620 metres (25,000 feet) or more. One of these peaks, Mount Everest, is the world’s highest mountain, at 8,848 metres (29,028 feet). This ancient marine sediment was thrust upwards when India, then an island, moved north and collided with the Asian continent. The principal phase of uplift began 65 million years ago and is still continuing, though uplift rates have been waning for the past 12 million years.

Formation of Mountains

Geologists recognize that movements in the earth’s crust, such as those that formed the Himalayas, have created most of the major mountain belts in the world. According to the theory of plate tectonics, the earth’s crust is made up of about a dozen large rigid plates that move a few centimeters per year independently.   wpe1B.jpg (17633 bytes)

The tallest and most spectacular mountains form along convergent plate boundaries, where the adjacent plates are moving towards one another.

Uplift

A collision between plates triggers deformation and thickening of the crust, which in turn leads to crustal uplift and mountain formation. A common process produced by horizontal compression is the deformation of layers into folds or wrinkles.

The Himalayas, for example, rose as a result of the compression and deformation that accompanied the collision of the Indo-Australian Plate with the Eurasian Plate. Compression generated by the collision of the African Plate and the Eurasian Plate formed Europe’s Alps and the Jura Mountains.

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Some mountain belts, such as the Andes in South America, result from the convergence of a continental plate and an oceanic plate. In these cases, the heavier oceanic plate is subducted, or forced under, the continental plate and partially melts, generating new magma. This magma solidifies as light, relatively buoyant rock beneath the mountains and helps cause uplift. Similarly, most of North America’s Rocky Mountains were formed in response to the subduction of oceanic plates beneath the plate margin of western North America. This kind of mountain building is often called orogeny.

Local uplift can also result from continental extension or rifting, the process that eventually breaks continents up into two or more pieces. Usually, rifting within continents is confined to long, narrow zones bounded by normal faults with a central downdropped block and uplifted sides. The Great Rift Valley of eastern Africa is a famous example of a continental rift. Basin and mountain structures such as those of Nevada in the United States and the Mexican state of Sonora are also due to crustal extension and normal faulting, but over a broad area rather than confined to a narrow rift valley. Crustal extension also occurs in the oceanic realm. In fact, the mid-oceanic rift system, which is almost entirely under water, is the longest continuous mountain belt on the earth, extending into all the major oceans.

Volcanoes

Mountains formed by volcanic activity are well known because of their usually isolated occurrence and the danger they pose. Most spectacular are the conical composite volcanoes, such as Mount Erebus in Antarctica, Mount Vesuvius in Italy, and Mount Fuji in Japan.   wpe19.jpg (15969 bytes)

Shield volcanoes, typified by Mauna Loa and Mauna Kea in Hawaii, US, are broad shield-like masses formed by fluid, wide-ranging lava. Volcanoes are associated with plate boundaries and form over subduction zones and in rifts, although volcanoes can also form within plate interiors, such as those over “hot spots” under the oceans.

Erosion

Mountains are usually very temporary features in terms of geological time. Many forces are constantly at work to erode them. Air, water, and ice cause the physical and chemical breakdown of mountain rocks that are exposed to the elements.   wpe18.jpg (14175 bytes)

Rain erodes weakened rock exposures, and streams carve deep gullies and ravines in mountainsides, mainly during flooding.

The products of erosion—sediments—are carried towards the sea by rivers and streams. Coarse sediment in the form of boulders and gravel often settles at the foot of mountains in alluvial fans. Finer sediments in the form of sand and mud are more easily carried longer distances. Eventually, mountains are eroded down to the level of the surrounding land, and most of the resulting sediment solidifies into sedimentary rock along river courses and near the seashore.

Glaciers are masses of ice that are so large they actually flow under their own weight. They constitute a slow-moving but very powerful erosive force. The bottom of the thick ice digs into the surface, picking up rocks and boulders, which add to the grinding and scouring process. The motion of glaciers has created huge U-shaped valleys and fjords in different parts of the world. Glaciers exist on many mountains, such as Grossglockner in the Austrian Alps, Mount Rainier in the Cascade Range of the northwest US, and Illimani Peak in the Real Mountains in Bolivia.

Gravity also has an erosive effect. Weakened rock on steep slopes may suddenly give way and fall down a mountain’s flanks in landslides. These mass movements carry tremendous quantities of surface material. Wind erodes rock over time, especially when the wind carries small rock particles. Plants also contribute to erosion when their roots spread into cracks between rocks, slowly prying apart the rocks.

Humans significantly increase soil erosion on mountains through deforestation and overgrazing, particularly on steep slopes. Soils lose cohesion and easily succumb to water erosion.

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Once-protected surfaces become more vulnerable to constant winds, and landslides become more frequent. In addition, hiking and vehicular traffic in sensitive areas or off designated paths lead to damaging erosion

The effects of erosion can create topographically rugged areas. Rocks of different composition resist erosion differently, meaning that areas of relatively hard rock may stand high above areas of softer, more easily eroded rock. The Massif Central in France and the Lake District in the United Kingdom are good examples of mountains created by the forces of erosion. In the US, a part of the Ozark Plateau—also known as the Ozark Mountains—in Arkansas and Missouri is another example.

Elevation

The elevation of a mountain peak is the height of the summit above sea level. Yet the appearance of mountains can be deceiving. Some high mountains nestle among other high peaks, and their summits do not appear to be much higher than the surrounding topography. In contrast, some mountains, particularly lone volcanoes such as Mount Egmont in New Zealand, rise dramatically from sea level to dominate the low-lying landscape. wpe17.jpg (13951 bytes)

An island that barely breaks the surface of an ocean may actually be the tip of an immense mountain that extends for thousands of meters down to the bottom of the ocean. Mauna Kea is the tallest mountain in the world when measured from its base to its peak. Its entire height, about 9,800 meters (32,000 feet) above the ocean floor, is higher than if Kilimanjaro, the highest mountain in eastern Africa, and Mount Fuji, the loftiest in Japan, were placed one on top of another.

Humans and Mountains

Mountains affect life in many ways. Apart from their obvious mineral, forest, agricultural, and recreational resource value, they exert a significant influence on climates and help determine the course of economic and historical trends.

Exceptionally high mountains, such as the Himalayas in Asia, markedly affect patterns of climate and weather over vast areas of the earth because they stand as barriers to regularly circulating air masses. Moisture carried inland by the westerlies from the Pacific Ocean, for example, falls as rain and snow on the windward sides of the Sierra Nevada of North America and the Andes of southern Chile. The leeward, or inland, side is drier, and the land beyond is frequently arid. This weather pattern is called the orographic effect.

The influence of mountains on the development of the western US demonstrates the importance of mountains to the history and economy of various nations.

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The first white travelers and settlers, and then the earliest railways, avoided mountain crossings because of the dangers and costs involved. Later, prospectors discovered vast deposits of valuable minerals in primarily mountainous areas. The lure of “striking it rich” drew people and railways west despite the hardships encountered in traversing the passes. As a result, settlers established transport routes through the mountains, with large populations centered about them; most of these remain today.

The political significance of mountains has been evident throughout human history. Mountain barriers with their relatively narrow and easily defensible passes have made various ranges natural political boundaries, second in strategic importance only to oceans and seas.

For more information on Mountains, go to:

    * Hydrological Cycle

    * Rivers

    * Rocks and Rock Cycle