What separates the crust from the mantle?
114510
Like pauliegone said, the lithosphere does in a way seperate the crust from the mantle.  The tectonis plates (crust) are supported by this semisolid layer.  However, the lithosphere is considered, by some scientists, part of the mantle.  So, it depends on which scientists you believe, although I believe that pauliegone is correct.
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
735109
Mountains are formed in the process known as plate tectonics. The earth is made of 6 major plates which are located on the earths crust. below the crust is an area known as the mantle which is lava which is very viscous. The Mantle has whats know as convection currents. these are slowly spinning sections of the mantle. Some are spinning clockwise and others counter. During mountain building there are 2 plates, one on the are of the mantle which is spinning clockwise and another on the current which is spinning counter clockwise. This allows the 2 plates to move in opposite directions which are known as divergent boundary's. Some areas however and spinning in a way to allow the plates to push together known as convergent boundaries. When this occurs you get mountains forming because the 2 plates are pushing together with a lot of force and over millions of years you get mountains rising.
79926
Careful: The questioner is correctly stating that magma is inside the earth's crust (or lithosphere).  Lava is magma that has erupted.  Magma rises up from within the lithosphere because it is more bouyant (wants to float) that the dense rock around it.  Lava is different, once it's on the surface, it does tend to flow with gravity, like water.
29120
Here is a chart of various estimates of the mantle's composition that have been made:\nhttp://www.mpch-mainz.mpg.de/~jesnow/Ozeanboden/2004/Lecture4/Composition.html\n\nThe answer in terms of minerals is (I quote) "The uppermost mantle is comprised of a peridotite with about 60% olivine 30% enstatite 6% clinopyroxene, 2% plagioclase and 2% spinel. At slightly greater depth, the plagioclase disappears and is replaced by spinel and clinopyroxene. Deeper still, garnet appears." from the above site. \n\nThe other thing you should realize is that while the earth's mantle may be 'plastic' it is not molten. From Wikipedia: "Although these temperatures far exceed the melting points of the mantle rocks at the surface, particularly in deeper ranges, they are almost exclusively solid. The enormous lithostatic pressure exerted on the mantle prevents them from melting."  From: http://en.wikipedia.org/wiki/Mantle_%28geology%29\n\nMagma coming from volcanoes actually originates in the asthenosphere, which is above the mantle.
1150478
It's widely believed in the scientific community that the earth has a liquid mantle (that's where magma/lava comes from) and a solid super-hot iron core.  Good luck digging through that.
575540
Divergent Boundaries...\n\nContinental/Continental: rift valleys i.e. East African Rift Valley\n\nOceanic/Oceanic: new crust is being formed on the ocean floor at oceanic ridges. The Mid-Atlantic Ridge is an example. The U.S. moves about 5cm away from Europe each year b/c of this.\n\nConvergent Boundaries...\n\nContinental/Continental: Both are of the same density & both are less dense than the molten material beneath so neither will be subducted. They form folded mountain chains such as the Appalachians of the U.S. & the Alps of Europe.\n\nContinental/Oceanic: Ocean crust is much denser & will be subducted under the continental. Friction from plate movement underneath the crust will cause melt & the crust will thin causing some volcanic mountains to appear.\n\nOceanic/Oceanic: One of the oceanic crusts will be subducted & a trench will be created. Volcanic island arcs are associated w/ this type of boundary.
716343
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.
369103
Well, the upper mantle, more specifically the asthenosphere, is a plastic- by which I mean solid but able to flow- layer on which all of the crustal plates "float". Therefore, you can say that the asthenosphere is responsible for continental drift, and is thus the direct cause of earthquakes, volcanoes, and all other geologic events on our fair blue planet. Come to think of it, the mantle can be said to be one of the factors that influenced life itself in its long development over the past 3.8 billion years! As the earth's crust cooled, volcanoes-caused by upwellings in the mantle- released carbon dioxide and other compounds into the primordial atmosphere that were used by early life for nourishment. They also released a portion of the water vapor that now exists as a liquid across 2/3 the Earth's surface as water. Therefore, the mantle, in a way, is directly related to the origin of life, and, in turn, human life.
751689
The crust and mantle are generally solid.  The inner and outer core are molten rock and metal...very dense, but still liquid.
108402
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).
603848
Continental/Continental plate convergence.\n\nThis happens during mountain building episodes called orogenies.
985501
Nice idea.... but there is a BIG hole in your theory:\n\nThe moon broke off from the earth somewhere between 3.5 and 4.5 billion years ago.... i.e. the Hadean... the more specific name for the earlier Precambrian.\n\nPangaea didn't even begin moving together until 1.1 billion years ago, and wasn't together as one continent until about 500 million years ago.... during the Permian.\n\nOh... and tectonic plate movement is a result of thermal flows in the mantle.\n\nPangaea has nothing to do with the moon, sorry to say.
870655
Magma, or molten rock located beneath the earth's surface, cools upon reaching the surface to form the crust. This crust is moved away from the location of upwelling by thermal convection currents in the semi-plastic mantle. The crust is then resorbed back into the mantle upon meeting another, less dense (more buoyant) crust. \n\nThere are two types of crust: oceanic and continental. Each are made from different minerals, resulting in oceanic crust being 'heavier' (denser) and thus sinking below the 'lighter' (less dense) continental crust at convergent boundaries. The earth's crust is in a state of constant motion (or, in some places, no motion, but a building up of energy) called plate tectonics. \n\nSee the wikipedia link below for more details. Hope that helped.
169484
Asthenosphere. \n\nThe asthenosphere is believed to be a ductile zone, probably around 1400-1600 degrees C, that flows slowly in response to stress. It is not liquid. The applied pressures are above 100 MPa (14,500 psi). Various sources estimate its thickness at 180-200 km.\n\nI've added a link to one of my previous answers explaining plate tectonics, and a definition from Schlumberger, and another from USGS.
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.
655694
It cools as it nears the atmosphere, and finally where we are it's cool enough for us to have evolved to ask the question.\n\nIn fact, the crust is maintained at a rather low temperature  - around 50 degrees F all the time - just 50 to 100 feet down or so. After that the temperature starts increasing. At between 18 and 1800 miles down, it's up at around 212 F (boiling point of water) due to pressure of that 18-1800 miles of rock (the range is wide because at some points in the ocean the mantle is closer to the crust). That's where mantle takes over.\n\nThe basic answer is that we're at least 1000 miles from the mantle. So when you say the mantle is "just" beneath the crust, you're talking about a pretty significant distance.