Molten rock can either be an “inny,” intruded into another rock, or an “outty,” extruded onto the surface of the earth. Just like an old-fashioned lava lamp, molten rock originating in the mantle or lower crust of the earth, is forced up because of its buoyancy. Molten rock is lighter than solid rock so it’s pushed upward by the extreme pressure inside the earth.
The molten rock advances by going up cracks, fissures and weak spots in the earth. It can even melt the rock above and advance that way. Javascript is required for you to be able to read premium content.
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