a kind of force that gets exerted as tectonic plates push against each other?
103247
The kind of force? This is normal force - the deformation incurred along a plate boundary (be it convergent or strike-slip) is caused by the repulsive force of particles of baryonic matter. It's the exact same force that is exerted when you push your hand against a wall.\n\nWhat drives plate motion is convection of the underlying magma, which is heated by nuclear decay deep in the earth.\n\nEarthquakes are the result of stored energy from continued strain on a region. They aren't really a force themselves, they are simply the result of a release of stored energy when rock surfaces slip suddenly and release P and S waves. (Along with a whole bunch of other waves, Love and whatnot, I can't remember everything)
668139
I remember reading somewhere that the great New Madrid earthquake in the early 1800s was so powerful that it caused the Mississippi River to flow in the opposite direction for a time.  I imagine that tectonic activity - movement that changes the shape of the earth's crust - would do it.
809527
I think its called 'subduction', where one tectonic plate goes under another. It occurs at 'subduction zones', such as on the west coast of the United States. The reason it occurs is that one plate is expanding and the edges need to go somewhere (under another plate). For example, the Atlantic plate is expanding from the center because there is a north-to-south line of underwater volcanoes, spewing out magma and forcing the 2 halves of the plate apart to the west and east.
92719
Let's consider a deep-sea diver. The pressure pushing on the diver is less at shallow depths than at greater depths. This is because at shallow depths, there is a shorter column on water above the diver than there would be at greater depths. But the pressure the diver feels is not just felt from above! The force is transmitted through the fluid and pushes the diver from all directions, even from below. \n\nPressure within the Earth can be thought of the same way that we think of water pressure on a diver. Under the surface of the ocean, you are under pressure from all directions because of the weight of the column of water above you. Within the Earth, an object is under pressure from all directions due to the weight of the column of rock above the object. This pressure is often called confining pressure, because it is the push from all directions that tends to confine material to the smallest possible volume (space).
819002
When two plates collide, they BOTH begin to go under a bit.  However, when a continental, and an oceanic plate collide, the oceanic plate ends up going under more.  Why?\n\nFor one thing, the continental plate is up higher than the oceanic plate to begin with.  After all, continental plates are always above sea level, and oceanic plates are always below sea level.  With the advantage of heighth, the continental plate usually pushes the oceanic plate below.\n\nFor another thing, the continental plate is thicker than the oceanic plate, and therefore is going to be harder to crumple, squish, or flatten.\n\nAlso, the oceanic plate is already under an enormous downward pressure from all of the ocean on top of it.\n\nAdditionally, continental plates are lighter.  They were formed by materials on the primordial earth that had floated to the surface, while oceanic plates are formed out of the magma from the center of the earth, which was below the continental plates because it was heavier at the time the plates were forming.\n\nAnd finally, wet rocks are a great deal softer than drier rocks, so the continental plate is harder to bend or break than the oceanic plate, which is soaked all the way through.
854011
Earthquakes are the Earth's natural means of releasing stress. When the Earth's plates move against each other, stress is put on the lithosphere. When this stress is great enough, the lithosphere. \n\nAs the plates move they put forces on themselves and each other. When the force is large enough, the crust is forced to break. When the break occurs, the stress is released as energy which moves through the Earth in the form of waves, which we feel and call an earthquake. \n\nThe earth is made of around 7 major plates. These plates are part of the earths crust and are floating of top of an area of the earth known as the mantle. This is the driving mechanism for the plates. Most Earthquakes are caused by Plate Tectonics. The earth's crust consists of a number of sections or plates that float on the molten rock of the mantle. These plates move on convection currents caused by heat rising from the center of the earth. The hot magma rises and spreads out on the surface, creating new crust. The crust spreads out forming a new plate until it meets another plate. One of the plates will be pushed down into the interior of the earth and reabsorbed into the mantle. Plates can also be compressed to push up mountains when they collide or move sideways along what are known as transform faults. the other 2 faults are known as divergent faults which is when 2 paltes slowly move away from each other and converegent faults which is when 2 plates push against each other.\n\nThe plates are the Earth's crust that float on the molten rock in the center of the Earth. Most of the inside of the Earth is so hot that the rock just simply melts away. The molten rock, which is also known as magma, bubbles up very slowly in great currents under the surface of the Earth. The crust that floats on the magma moves with it. The Plates are just pieces of the crust. Just like a giant jigsaw puzzle. The part that makes it hard to understand is that it all moves extremely slowly. Just a few cm a year, roughly at the same rate a your finger nails are growing. \n\nHope this has helped you out a bit
168771
The outer crust of the earth is made up of sections of crust.  These sections are called tectonic plates and they float on the magma (lava) below.  When the plates shift, the friction between them causes earthquakes.
24692
The best answer from the above choices: \nSlow moving convection currents within the molten aesthenosphere supply new material to the spreading centers in the earth's ocean floors and other places. These currents are thought to provide force to cause the motion of the oceanic plates, either directly, or indirectly through the mid ocean ridge building process. \n\nSubduction is only one part of the process of plate tectonics, that does provide some driving force by pulling the subducting plate downward. \n\nGravity has a role as well, as without gravity, the mid-ocean ridges would not have the weight to provide force with which to push the plates apart at the spreading centers, and the subducting plates would not have the force to pull plates. \n\nThe earth's magnetic field may have the least to do with plate tectonics, possibly no role at all.
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.
813186
a counterbalancing force or system of forces.
919770
It is a force that pulls you to the earth.
363137
I think Stillkelsie and GruHairy have the best answers.  \n\nIf one (or both) of the colliding plates are oceanic plates (thinner and a bit denser), one will slide underneath the other and be pushed down.  You'll typically get a subsea trench where the two plates meet, such as the Marianas Trench in the western Pacific Ocean.  After the sliding's gone on long enough, some of the "pushed-down" plate will melt, and the lighter melted rock will try to rise to the surface, where it can form volcanoes or cool underground as granites and such.\n\nIf two continental plates (thinner and less dense than oceanic plates) collide, they'll tend to mash each other and "pile up".  The Himalaya Mountains, earth's tallest, were formed when the Indian continental plate collided with Asia.\n\nYou get earthquakes associated with both types of collisions.
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!
797755
It happens in the brittle part of the crust, which is not usually deeper than 20 km.\n\nHere's the jist:\n\nIt all comes down to stress and strain. It is not 'the plates rubbing together' as many people say; or at least that's a very simplistic view.\n\nPlate tectonics causes stress on the continents and oceans, all over the surface of the earth. In some places, the stress is very small (usually within the plates). Elsewhere, the stress is high, usually where the plates meet each other. Since each plate moves, when two come in contact, the stress each other. They can push on each other and cause compressional stress, they can pull with extensional stress, and they can slide past or shear each other with tensional stress.\n\nFaulting, causing earthquakes, comes from the fact that this stress is building up all the time, but rocks and continents are strong materials. Just like hitting a rock with a small hammer, you do put stress on it, but a small amount. It would take a sledgehammer to put enough strain (effects and accumulation of stress) to build up and cause breakage. In the earth, the area around an active fault builds up strain from the stress of plate tectonics. Most faults become locked, because of this strength, and thus can not release their strain. Away from the fault, the stress produces very small and slow movement of the rock masses as a whole. Eventually, the strain is too much and the rest of the plate has moved too far and the fault releases the strain build-up all at once in a big stress release called an earthquake. This is called the elastic rebound theory, and it explains most (but not all) movements.\n\nThis is why an earthquake's size is relative to the fault size. The bigger the fault, the bigger the strain build up, and the bigger the release in an earthquake. Subduction zones and collision zones, where large portions of plates actually can rub together as a whole, have the really big earthquakes, like the 2004 Sumatra earthquake. In other plate boundaries, the entire plate boundary does not act together, so the faults become spread out and many faults take up the strain from the tectonic stress, like with the San Andreas Fault in California (it only takes up ~3/4 of the stress between the plates).\n\nEarthquakes are really tricky things; there is still so much we need to learn. As of now, there is no way to predict them, but we can say where the danger is highest and about how long between events.
119467
Plate tectonics is deeply connected with physics, and was discovered by geophysicists using techniques from physics.\n\nFor example:\n\n1. Fluid mechanics\n2. continuum mechanics\n3. electromagnetism\n4. newton's laws\n\nPlate tectonics was discovered by looking at stripes of magnetization on the sea floor. These are from the earth's field, which is caused by a dynamo, which is very complicated physics, involving electromagnetism and fluid mechanics. The plates move because of entrainment by moving fluids beneath. There is a lot of thermodynamics involved in the heat transfer and the cooling of the plates after they emerge from a midcean ridge; they contract as they cool. There is continuum mechanics involved in the deformation of the plates as they collide or get subducted. Islands on the plate surface can cause the plates to flex, and this is studied by continuum mechanics. One could make a very extensive list, that would probably include quantum mechanics, and even nuclear physics (which creates the heat that drives the plates), and only exclude quantum effects.
950622
the tectonic plates that shift happen  underground, if your lucky to see a plate shift at ground level your truly lucky, these plate shifts cause earthquakes so please be careful.
525704
look up plate tectonics