If there is lava inside earth why it comes out of earth's crust
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due to temperature it comes out of the earth crust
raunaksankhwar:
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Well, volcanoes. And the lava in volcanoes comes from deep in the earth where everything is molten, right? Wrong! It’s true that as you go deeper into the earth, things heat up, but the earth isn’t a crispy rock shell around a gooey molten center. The crust, mantle and inner core of the earth are all solid rock (or iron in the case of the core). The only large portion of the earth’s interior that is liquid is the outer core, and lava does not come from there (again, if it did, it would be molten iron).
People get confused on this point because in school we learn that the mantle flows and convects heat from the core to the surface. Well, that’s true, but it’s misleading. The mantle flows over timescales of millions of years. If you could dig down and pick up a piece of the mantle and whack it with a hammer, it would break. See, hot rocks are a lot like silly putty. Set a ball of silly putty on a table and don’t touch it and it will slowly deform and flow and flatten. Whack that same silly putty with a hammer or pull it really sharply and it will shatter or snap. So that’s how the mantle can flow, given billions of years, but still act like a hard, brittle rock over shorter time periods. The same happens with lava on the surface.
So if the whole mantle is solid, where does hot, molten, fluid lava come from? Well, in certain places, the crystals in the mantle or lower crust can begin to melt. This can happen if there is a hot upwelling from deeper in the earth, as is the case for the Hawaiian islands, or if continental crust is being dragged down into the hot mantle. Temperature, pressure and water are the three main culprits in melting rock, and I’ll explain why.
Temperature is the obvious case: heat something up and eventually it will melt. This is the main source of melting for Hawaii, since it is sitting on a mantle “hot spot” but the other two play a role as well.
People get confused on this point because in school we learn that the mantle flows and convects heat from the core to the surface. Well, that’s true, but it’s misleading. The mantle flows over timescales of millions of years. If you could dig down and pick up a piece of the mantle and whack it with a hammer, it would break. See, hot rocks are a lot like silly putty. Set a ball of silly putty on a table and don’t touch it and it will slowly deform and flow and flatten. Whack that same silly putty with a hammer or pull it really sharply and it will shatter or snap. So that’s how the mantle can flow, given billions of years, but still act like a hard, brittle rock over shorter time periods. The same happens with lava on the surface.
So if the whole mantle is solid, where does hot, molten, fluid lava come from? Well, in certain places, the crystals in the mantle or lower crust can begin to melt. This can happen if there is a hot upwelling from deeper in the earth, as is the case for the Hawaiian islands, or if continental crust is being dragged down into the hot mantle. Temperature, pressure and water are the three main culprits in melting rock, and I’ll explain why.
Temperature is the obvious case: heat something up and eventually it will melt. This is the main source of melting for Hawaii, since it is sitting on a mantle “hot spot” but the other two play a role as well.
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