why do plates float on the lothosphere?
138727
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.
236062
Because of its shape. \n\nA ship, when placed in water, forces some volume of the water to move (displace) and make place for the ship. If the weight of the displaced water is more than that of the ship, the ship will float. \n\nIn other terms, the average density of the ship is less than that of water and hence it floats on water.
810641
Use Archimedes's buoyancy principal.  The weight outside represents the response of mass to the Earth's gravity.  The weight in water represents the displaced water's weight.  Use the ratio to get the answer.  HINT: if you convert to mass, the answer almost gives itself away.\nThe displaced water has a well known density.  That density will give the volume of the both the displaced water and the object displacing it.
710689
It does not help.  It is the LACK of sufficient conduction in the mantle that forces the core to get rid of its heat by mantle convection instead.  If the mantle conducted better, it wouldn't need to convect, and then there would be no plate tectonic movement at all.
219728
Maybe you have a large ore deposit beneath your location. This could generate a strong field that the polarized molecules would be attracted to. If it's closer to the upper part of the hill and big enough, it could also provide a small amount of gravitational attraction that could be pulling the water uphill.\n\nThe gravitational field of the Earth varies from place to place at the surface. We see this all the time when we take very sensitive readings. It is possible that a gravitational anomalies can be enough to cause odd effects at the surface.
109251
plate tectonics provides an explanation for the continental drift hypothesis.
404666
By the pull of earth's gravity
155676
This is the Wilson Cycle, and it is driven by plate tectonics. \n\nContinents are composed of relatively light weight felsic igneous rocks such as granites and granodiorites. Ocean basins are composed of mafic igneous rocks like basalt and gabbro that are heavier than continental crust. Since the earth's mantle is plastic, these different masses of rock tend to 'float' at different levels. This is called isostacy.\n\nOceanic plate motion originates at the mid-ocean ridges, pushing oceanic plates outward towards the continents. This motion and force is far from being uniform from one ocean basin to another, and is not even consistent along the length of the mid-ocean spreading centers. \n\nWhere oceanic plates meet continental plates there is a convergent plate boundary and generally this leads to subduction of the oceanic plate. There is considerable force however, and the style of subduction does vary. Since the forces that are being applied, as well as the resistance of the continental plates all are varied, there are inequities that cause the continents to move in one direction. Eventually this motion results in a collision of continents called a supercontinent because continents will not subduct under one another. India and Asia, and the Himalayas are a great example of a continental convergent plate boundary. Eventually the convection forces that cause the supercontinent to form will begin rifting it apart again creating new smaller continents. \n\nHere is a model of the Wilson Cycle:\nhttp://csmres.jmu.edu/geollab/vageol/vahist/wilsonsimp.html
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.
794138
The continental plates do not actually 'drift' as you may think of an ice cube 'drifting' in water. Nor are the plates all connected together like one would view a jigsaw puzzle.\n\nThe first idea you have to realize is that the continental plates overlap each other. The 'outlines' you see that appear jigsaw-like are more often than not areas where two plates meet, and one plate is actually going under  the one next to it- this is called 'subduction'.\n\nWhich plate goes under which plate depends on the age and weight of the plates-- continental crust is lighter than oceanic plate, so more often than not it is the oceanic piece of the plate that will 'subduct'.\n\nThere are areas, however, where the plates do actually meet like a jigsaw puzzle-- these places are known as "Strike-slip" faults, where two plates slide past each other rather than 'subducting'.\n\nAs for the plates moving, that happens due to the upper mantle (the liquid part under the crust) creating convective currents-- these 'currents of mantle material' cause the plates to move and subduct (or slide past each other!)\n\nAnd yes, there are plates where continental crust and continental crust meet. What happens then? More often than not, mountains form-- The Himalayas are a prime example of this situation (the Indian plate smashed into the Asian plate).\n\nThere's more to it, but I hope this helps a little bit!
327692
because there is a subduction zone. One plate goes under the other and melts into the earth's mantle.
738049
b) changes\n\nwhen a plate moves it can do a number of things. it can make a mountain, volcano, island, etc.\n\nit doesnt collapse (stupid answer), it wont melt (why would it? all thats happening is a plate moving, that wouldnt melt earth) and it doesnt shrink just because it moves.
195652
the earth is a oblate spheroid....we do not fall to the edges because of the gravitational pull...
514578
Yes, Gravity works everywhere, but there are some kinds of gas that result lighter than gravity so they float or even goes up.
594942
It is said that the SHIP sinks in the water in that area.\nThat's may be due to higher gravity or some other force which is still unknown.
958787
Mantle convection moves the plates\n\nAt plate boundaries, there are many forces at work: ridge push, slab pull, trench suction, slab roll back and basal shear resistance to name a few.\n\nThe links go into more detail about the forces and where they working.
704408
wikipedia.org\n\n"On Floating Bodies (2 volumes) \nIn the first part of this scroll, Archimedes spells out the law of equilibrium of fluids, and proves that water will adopt a spherical form around a center of gravity. This was probably an attempt at explaining the observation made by Greek astronomers that the Earth is round. Note that his fluids are not self-gravitating: he assumes the existence of a point towards which all things fall and derives the spherical shape. One is led to wonder what he would have done had he struck upon the idea of universal gravitation. \nIn the second part, a veritable tour-de-force, he calculates the equilibrium positions of sections of paraboloids. This was probably an idealization of the shapes of ships' hulls. Some of his sections float with the base under water and the summit above water, which is reminiscent of the way icebergs float, although Archimedes probably was not thinking of this application. "\n\n\nOK - I thought that this might be easy to research, however, your teachers have come up with a good one as it does not seem that you can use a direct search to find much.  So, now we try some other ideas:\n\n* my gut feel is that you should turn up the edges of the foil to create a pan type struture (think of your mothers deep pans with 3" to 4" side - roll the edges for strength and bold the corners in).  This would be a version of a flat boat.  You should practice to ensure that it works.\n\n* also, why not try to contact some actual boat engineers!  - try searching under "aluminum boats" and see if you can sent them emails to try to talk to an actual boat engineer.\n\n* I would also suggest trying to contact makers of aluminum foils to see if any of their engineers could give you any ideas.\n\n* Since this type of contest is run at other locations, you might also try tracking down some of the past winners to see what they learned and what their secrets were.\n\n* then try looking for foil boat !!!\nhttp://juniorengineering.usu.edu/workshops/buoyancy/boats.html\nhttp://www.new-sng.com/foilboat.cfm\nhttp://www.sciencenetlinks.com/Lessons.cfm?DocID=143\nhttp://pbskids.org/zoom/activities/sci/boatsafloat.html\nhttp://www.newton.dep.anl.gov/askasci/phy00/phy00291.htm\nhttp://www.nps.gov/archive/miss/programs/brj/brjactivities/aluboat.html\nhttp://education.jlab.org/beamsactivity/6thgrade/designandengineering/designandengineering.pdf\nhttp://www.sciencenetlinks.com/lessons.cfm?BenchmarkID=3&DocID=143\nhttp://www.lessonplanspage.com/ScienceWillTheBoatSinkOrFloat4.htm\nhttp://www.monroe2boces.org/programs.cfm?subpage=955\nhttp://www.nps.gov/archive/miss/programs/brj/brjpdfs/aluboat.pdf\nhttp://users.marshall.edu/~bady/rsi/4th/4bouyancy.html\nhttp://www97.intel.com/en/ProjectDesign/UnitPlanIndex/FloatThatBoat/\n\n\n* Ah Ha - and the secret is (as I suspected):\nhttp://www.nps.gov/miss/forteachers/brjralumboat.htm\n\nNote to teacher:\n\nGive students the opportunity to be as creative as possible with the hull shape. Make no suggestions, unless to show how to fold up one side to make an edge. The best designs are flat barges with small sides. The placement of pennies also makes a difference in the number held. The record for one sheet of 8" x 12" foil is around 280 pennies. Recycle the foil along with your pop cans.\nScience Museum of Minnesota, 2001.\n\n\nOK, now that you know how to win the contest, I would still recommend contacting the engineers at the boat companies and the aluminum foil companies and be ready to talk about what you learn as you win the contest.  You will impress the judges so much with your knolwedge and skill of floating all those pennies that they will have to give you the prize.\n\n\nGood Luck.