why did mount st helen form??
962253
Mt. St. Helens is a subduction volcano.\n\nVolcanism in subduction is caused by volitals, like H2O, CO2. These are carried down by the oceanic plate, mainly in the form of weak minerals. These minerals break down with pressure and temperature into stronger minerals that don't contain water and carbon dioxide. The leftover gases and liquids travel into the mantle (the mantle wedge) and hydrate the mantle, causing melting. The melt rises and then... volcano!
851419
the gases build up that pushes the molten up, if there is snow causes hazardous and gaseous mud slide down the mountain.  Causes some tremors like earthquakes. Hazardous smoke (ash) cloud.  look up mount saint helens in Washington or the volcanoes in hawaii.  plus there are many throughout south america.  Pictures of mt. st. helens are awesome. I went there after it happened in 1980 it was phenomenal!  I felt the tremors up by bellingham. it was cool.
936340
Mushroom clouds form as a result of the sudden formation of a large mass of hot low-density gases near the ground creating a Rayleigh-Taylor instability. The mass of gas rises rapidly, resulting in turbulent vortices curling downward around its edges and drawing up a column of additional smoke and debris in the center to form its "stem". The mass of gas eventually reaches an altitude where it is no longer less dense than the surrounding air and disperses, the debris drawn upward from the ground scattering and drifting back down (see fallout).\nhello, use the link below to get more info.
1056316
It is caused by the movement of large plates on the earth's crust.  When these plates move into each other it causes a collision, which basicallly push them together - hence the reason for all the Mountains out west - 2 plates pushed together caused the ends to go up...hence mountains...but when these plates move you get the shaking, thus causing an earthquake.
711017
A destructive plate boundry causes one plate to be subducked below another, (sucked under basically) this causes it to melt and then rise to the surface where it forms the Mount Pelee volcano\n\nHope that helps
926785
Mountains are either volcanic or tectonic.\n\nVolcanoes:\nThere are several processes in Plate Tectonics that cause volcanism, but they result in two main types of volcanism.\n\nVolcanism in subduction is caused by volitals, like H2O, CO2. These are carried down by the plate, mainly in the form of weak minerals. These minerals break down with pressure and temperature into stronger minerals that don't contain water and carbon dioxide. The leftover gases and liquids travel into the mantle (the mantle wedge) and hydrate the mantle, causing melting. The melt rises and then... volcano!\n\nThe other main cause is from rising mantle material, which forms decompression melting. Basically, hot mantle is kept from melting by the pressure of the earth at depth. When this material rises, the pressure drops much faster than the temperature, and thus it partially melts. This mainly occurs at divergent boundaries and hot spots, which are areas in plate tectonics that have rising materials or spreading.\n\nMountain Belts:\n\nNon-volcanic mountain belts are caused by compressive stress in plate tectonics. This can be 1. fold and thrust belts in highly compressive subduction zones (almost always from oceanic beneath continental subduction, e.g. east Andes, Rockies) or 2. continental-continental collisions (e.g. Himalaya, Appalachian).
296747
Plates collide in areas called subduction zones.  At these zones, oceanic crust is subducted underneath continental crust due to its higher density.  Subduction results in great amounts of heat and pressure building up in the zone.  When these factors become strong enough, they are forced to the Earth's surface in the form of volcanoes.  That is why volcanoes typically occur along plate boundaries (e.g., the ring of fire).  However, volcanoes are not exclusive to plate boundaries.  They can also form over hot spots within the interior of the Earth.  The islands of Hawaii are an example.  The islands are formed on the Pacific Plate.  The plate is moving in a northwest direction, while the hot spot underneath the crust is stationary.  As the plate moves over the hot spot, volcanic eruptions occur.  The result is a new island being created.  The islands are actually the products of a series of shield volcanoes that grow in age as one moves to the northwest.
890910
Mt St Helens is in the Cascade mountains in Washington state. It is on the NORTH AMERICAN PLATE, near it's intersection with the Pacific Plate and Juan de Fuca Plate.\n\nSee this pic for details: http://en.wikipedia.org/wiki/Image:Cascade_Range-related_plate_tectonics.png
126957
Mt shasta is a stratovolcano and its eruption will probably look something like that of Mt. St. Helens because they form basically by the same process, the subduction of the pacific plate below the North American plate. The lava will be high in silica, which will make it sticky and probably explosive.
16395
This process is known as plate tectonics. The earth's surface is composed of large 'plates' which gradually move around over time. The movement is driven by convective currents of molten rock within the asthenosphere. Movement begins at the midocean ridges, which are actually larger than continental mountain ranges. As magma builds these ridges the weight of the material, combined with the convective flow causes them to push outward towards the outer parts of the oceanic plates. Some of these plates subduct (go under) the continental plates, or even other oceanic plates. This subduction process lifts continents higher and leads to mountain building. You can see some illustrations here:\nhttp://www.ucmp.berkeley.edu/geology/tecmech.html\nYou can watch animated versions showing the plate motion here:\nhttp://www.ucmp.berkeley.edu/geology/tecmech.html\n\nAs for parts of the earth falling into the ocean, that is just a not-so-serious thing that people say trying to explain plate tectonics. There are zones of continental crust that are rifting, being split apart, and these may eventually move below sea level. Some examples of this are the Great Rift Basin in northern Africa. The Red Sea is a rift zone that has submerged, and the Dead Sea is part of a rift zone. \n\nThese processes are quite slow on our time scale. The Pacific Ocean is spreading about 4-5 cm per year.\n\nAnd if you've ever heard that California is going to fall into the ocean- don't worry it isn't. The boundary between the Pacific Plate and the North American plate is actually within California, but the motion is such that Los Angeles is moving north towards San Francisco. Millions of years from now, Los Angeles may be moved north of San Francisco.
138413
Due to different tectonic plates that move in different directions, the Peninsula was formed. \n\nRight in the middle, the San Andreas fault will continue with the splitting apart of both plates, until the Peninsula and a part of California from the Sea of Cortes up to San Francisco will become an island and continue moving North toward Alaska, while the Continental Plate will continue to slide West in the next 5 million years.
211905
The world is divided up into different plates, which move around ever so slowly. Sometimes they collide, and a mountain is formed as the sides of the plates hit each other and push upwards. This is how the Himalayas were formed, and they are getting higher as the plates slowly push against each other. Where two plates push past each other, an earthquake can result. This is the case along the San Andreas Fault. Hope this helps!
992332
Volcanos tend to form at the points where tectonic plates meet.  One notable exception is Hawaii, which is formed over a hot spot in the middle of the pacific plate.
555826
It formed as a volcano, and was then changed in shape by glacial activity-this from a website:\n \nHoodoo Mountain  consists of a symmetrical lava dome, approximately 6 kilometers in diameter, surrounded on three sides by alpine glaciers. Only its southern slope, which extends down to the floodplain of Iskut River is ice free. Hoodoo's steep sides and nearly flat 900-meter summit suggest it formed as a subglacial tuya when regional ice sheets covered all but the highest peaks of the northern Coast Mountains. Subaerial lava flows which rest on glacial till along Iskut River indicate that volcanic activity continued after retreat of the ice. Radiometric dates of 0.11 and 0.09 million years are consistent with the age of other ice-contact features in the Stikine Volcanic Belt. \n________________________________________
263800
Yellowstone volcanics are a localized feature that has shot through the overlying crust.  This is determined largely through geochemestry and heatflow studies.  The Hawiaan Islands are formed as a result of a hotspot.  You can see that the overlying plate has been moving with respect to the hotspot because the islands formed one at a tine in a line, showing plate direction.\n\nMt St. Helens is the result of a process called subduction.  The oceanic Pacific plate is being shoved underneath the North American plate.  As that plate is pushed deeper and deeper, heat and pressure create a partial melt that can rise to the surface and create volcanoes.  Look at the Aleutian chain, those are also subduction volcanoes, only there you see oceanic crust shoved under oceanic crust
71801
It depends on the volcano.\n\nIf magma - molten rock - is erupted it forms new formations when it cools. On the big island of Hawaii, the volcanic eruptions have added a lot of new land to the island.\n\nIf it is a pyroclastic flow - fast, hot gasses and volcanic debris -  like the one that destroyed Pompeii or Mt. St. Helens, there may not be any new land created and the existing land will be radically altered.\n\nIn general, when a land based volcano erupts, the lava and stone and ash build up around the eruption site into a cone shape.\n\nUndersea volcanos spweing lava also build up, but not in a cone shape. Once the hot rock hits water it starts to cool into large pillow-shaped forms.
223014
Movement of the tectonic plates resulted in the breaking up of "Pangea", the super continent. Here is more information for you including a video clip on the last link. The video takes a bit to load.\n\nHave fun!