how is a mid-oceanic ridge formed?
475416
Nope; the oceanic plates are spreading apart, as new material (magma) is pushed up from below.  They are not crashing together at all.
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Volcanoes are a result of the Earth trying to lose its internal heat. If the Earth's interior was cold, there would be no volcanoes. So how does a volcano form hey.\n\nWell, deep inside Earth, between the molten iron core and the thin crust at the surface, there is the mantle, a large layer of rock that is largely solid, but flows like plastic. When, for various reasons, rock from the mantle melts, it sometimes moves to the Earth’s surface through weak spots in the crust, releasing heat, gasses, and rock, what do you get when you put all this together..... you got it,  a volcanic eruption.\n\nVolcanoes erupt because magma is less dense than the solid rocks surrounding it in the mantle of the earth. As it nears the surface, gases expand and boil out of the rock, and this force of explosion propels lava from the vent. \n\nVolcanoes can occur by themselves or in belts and chains. The location of these volcanoes splits them into three groups. Rift volcanoes, subduction volcanoes, and hot spot volcanoes. This has a lot to do with plate tectonics, or moving of the segments of the earth's lithosphere. \n\n· Rift volcanoes occur where the plates are moving away from each other. They fill the separations with lava flows, creating new sea floor and mountain ridges beneath the waves. \n\n· Subduction volcanoes form where the plates collide and slide over each other. They create ridges and peaks. The Ring of Fire is a famous chain of volcanoes that rim the Pacific Ocean. About 1,000 live subduction volcanoes occur in this ring, and in any one-year, approximately 40 will be in some state of eruption. The Ring of Fire is composed of stratovolcanoes, which normally occur in chains, and account for over 95% of the world's active volcanoes.\n\nHot spot volcanoes are the exception to the rule of volcanoes occurring along plate margins. There are constant zones of magma within the earth in some places beneath the plates. The magma pierces through the plate. As time passes and the plates move, new volcanoes appear, and the extinct volcanoes are carried away with the drift of the plates. The common forms of hot spot volcanoes are shield volcanoes, like Mauna Loa of the Hawaiian Islands.\n\nMany factors determine the location, appearance, and amount of activity of each volcano. The location and consistency of magma determine the type of explosion, which determine the type of volcano that is formed. \n\nVolcanoes are both facinating and deadly examples of natures power. They are natural wonders that should be not just appreciated, but studied aswell. \n\nSorry this is long its just I studied volcanoes at uni and just find them fascinating.
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.
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The mechanisms of tectonic plate movement is quite complex, but in its simplest terms, tectonic plates float on molten magma of the earth's interior. Convection currents within the molten magma behave similarly to convection currents in a pan of water being heated on the stove. Water on the bottom of the pan is heated and begins to rise because it is slightly less dense than the cooler water on the top. The cooler is slightly more dense and begins to sink. As this water is heated, it begins to rise, thus a convection movement or convection current is created in the water in the pan. \n\nMagma is far more dense than water and is much hotter, but it is still a fluid. Magma near the core is hotter than the magma beneath the crust. Hotter magma moves up, cooler magma moves down, very very very slowly, but none the less, it moves. The crust, a.k.a. tectonic plates float on the magma. Float some pieces of Styrofoam on the water in the pan. What happens? The foam moves around by the convection forces in the water.  Tectonic plates do the same thing. Its just not as fast.\n\nHope this helps.
107934
The Earth's rocky outer crust solidified billions of years ago, soon after the Earth formed. This crust is not a solid shell; it is broken up into huge, thick plates that drift atop the soft, underlying mantle. \nThe plates are made of rock and drift all over the globe; they move both horizontally (sideways) and vertically (up and down). Over long periods of time, the plates also change in size as their margins are added to, crushed together, or pushed back into the Earth's mantle. These plates are from 50 to 250 miles (80 to 400 km) thick. \nThe map of the Earth is always changing; not only are the underlying plates moving, but the plates change in size. Also, the sea level changes over time (as the temperature on Earth varies and the poles melt or freeze to varied extents), covering or exposing different amounts of crust. \nThe current continental and oceanic plates include: the Eurasian plate, Australian-Indian plate, Philippine plate, Pacific plate, Juan de Fuca plate, Nazca plate, Cocos plate, North American plate, Caribbean plate, South American plate, African plate, Arabian plate, the Antarctic plate, and the Scotia plate.
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The continental plates float on the LITHOSPHERE because the continents, including the mountain ranges, are composed of LIGHTER materials than the partial BASALT of which the seafloors are composed and of which the lithosphere is composed.  Even GRANITE weighs less.\n\nThe lithosphere is very hot in comparison to the crust of the earth.  The materials there are 'plastic' and flowing.  this enables crustal adjustments to granitational, earthquake and other stresses.\n\nIt is all somewhat similar to bread floating on the top of pea soup (representing the molten sea of cushiony basalt).  If you put two large pieces there (continents), ones that fill nearly the whole surface, and if you push one down, the other will rise.\n\nWith erosion onto the sea floor continental masses also become lighter.  This can make land masses rise.  The pressure of the ocean waters also keeps the continents up.\n\nThe heavier ocean floor plates dive under the continental plates where these two thrust into one another.  There are such areas around the Pacific rim.  Deep marine trenches are associated with these.\n\nLook on the internet for tectonic plates, deep marine trenches, basalt (also from Hawaiian volcanoes) and you will find lots of info.
712469
The earth's crustal plates float on a layer called the Mantle, and it is convection in this mantle which drives the continental drift or plate tectonics.
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Ophiolites are pieces of oceanic plate that have been thrusted (obducted) onto the edge of continental plates. They provide models for processes at mid-ocean ridges.
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When liquid magma comes out of the earths crust at the mid-oceanic ridge, it cools rapidly forming crystals. These crystals have magnetic properties that align the crystal according to the earths magnetic field at the time they cooled, similar to how a compass needle points north, the magnetism in the crystal indicates which direction was north when the crystal was formed.\n\nHowever, the direction that is north today, was not always north in the past, in fact many times in geologic history, the north and south poles were reversed entirely. This is reflected in the "magnetic bands" found in rock on the ocean floor.\n\nSo, if you imagine the Atlantic Ocean between the U.S. and Europe, there is a mid-ocean ridge between the two. If the plates never moved, then the magma coming out of this ridge would just pile up, but instead, this is the "engine" that moves the plates away from one another. As you move from the mid-ocean ridge towards the continents, the crystals in the rock have different magnetic orientations that show these flip-flops of the earths magnetic field through geologic history. Because this material originated at the mid ocean ridge, but is now closer to the continents, it shows that the earths crust, the floor of the ocean, is moving AWAY from the mid-ocean ridge and TOWARDS the continents.\n\nThere are a lot of  diagrams that would probably help you understand this better. CHeck out a geology book, or look online.\nGood Luck!
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What type of mountains? The largest mountain chain in the world is the mid-oceanic ridge and it is created by upwelling mantle. Other types of mountains are created by the subduction of basalt under continental crust (e.g. the Andes Mountains). Still other types of mountains are created by continent-continent collision (e.g. the Alps). Still other types of mountains are created by hot spot vulcanism (e.g. The Hawaii Islands). Other types of mountains are created by trans-pression (e.g. The Coast Ranges of California). Be more specific as to which type of mountains you refer.
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The outermost part of the Earth's interior is made up of two layers: above is the lithosphere, comprising the crust and the rigid uppermost part of the mantle. Below the lithosphere lies the asthenosphere, which is a more viscous zone of the mantle. Although solid, the asthenosphere has very low shear strength and can flow like a liquid on geological time scales. The deeper mantle below the asthenosphere is more rigid again.\n\nThe lithosphere essentially floats on the asthenosphere. The lithosphere has broken up into what are called tectonic plates—in the case of Earth, there are ten major and many minor plates. These plates move in relation to one another at one of three types of plate boundaries: convergent, divergent, and transform. Earthquakes, volcanic activity, mountain-building, and oceanic trench formation occur along plate boundaries. The lateral movement of the plates is typically at speeds of several centimetres per year.
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Oceanic crust is formed by volcanism at the mid-ocean ridges, also called spreading centers. Magma upwells from within the asthenosphere or mantle. It often does not erupt onto the sea floor but rises through complex cracks and fissures where it encounters cooler rock and sea water. Other areas actively erupt and lava flows in sheets typically less than 10 meters thick. For example, at the Juan de Fuca Ridge, the process creates about 6 meters of new crust in 100 years. Oceanic crust consists of basalt, often referred to as MORB (mid-ocean ridge basalt).
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The reponse is related to plate tectonics. The earth crust is composed of a larger number of plates that float, very slowly of course, over the liquid interior. Continents therefore move relative to each other. When two plates meet, generally one moves under the other and it is here that we find mountains and volcanoes.\n\nWhat relation with oceans? Well, between some of the plates there is an upwelling of new magma, new crust. This is for instance the case in the middle of the Atlantic Ocean. The new crust needs room and pushes the plates on the left and right away: the Americas are moving to the west, while Europe and Africa are moving to the east. \n\nOceans (ah, at last!) are watermasses in which such upwelling of fresh crust takes place. An ocean therefore is partly in two or more different plates. On the other hand, seas are bodies of water that are on one continental plate only, or on two plates were no new crust is formed.\n\nHere is a pictures of the different continental plates:\n http://en.wikipedia.org/wiki/Image:Plates_tect2_en.svg
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Composite volcanoes typically form along subduction zones (ocean - continent plate boundaries).  They tend to have higher viscosity magma (andesite and dacite) which allows for more gas pressure to develop.  This produces more explosive eruptions.\n\nSome examples of subduction zones are the western coast of the USA and South America.  The Cascades and the Andes were and are currently being formed by subduction related processes.
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It erupts from he center point of the ridge from underneath the crust of the Earth. The center is the oldest point, seeing as how the material flows away from the peak of the ridge. It's like Earth's pressure valve, Hawaii was formed a bit like this.
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It becomes rock on the surface of the ocean floor. It is eventually carried further & further away.\n\nSome older rock created by this process has already been "recycled" in the rock cycle; it became molten when it was subducted under continental plates.\n\nAn interesting fact is that as new rock is being created at the Mid Atlantic Ridge, the earth's magnetic field is being recorded right into the rocks. Any time there is a change in the direction of the earth's magnetic field it has been recorded.\n\n:)
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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.