Rocks come from magma, which is the molten material found within the earth. When magma cools, either above or below the earth's surface, it crystallizes and forms the igneous rocks that can later be changed into metamorphic or sedimentary rocks. Magma, which can be considered molten rock, is referred to as lava when it reaches the earth's surface.Continue Reading
The igneous rocks initially formed from cooled and crystallized magma can eventually be weathered down into fragments by the forces of erosion. They then become sedimentary rocks through the additional processes of compaction and cementation. Both igneous and sedimentary rocks can be transformed into metamorphic rock when subjected to pressure and temperature conditions other than those which originally formed them. Heat is produced by the friction generated by movements of Earth's tectonic plates, and the creation of mountains creates pressure. An intrusion of magma into surrounding rock can also be a source of heat. Overall, the temperatures and pressures needed to produce metamorphic rocks are much greater than those found on the earth's surface.
Each of the three major classes of rock can be transformed into one of the other classes through the continuing processes of heat, pressure and erosion. This ongoing transformation of rocks is referred to as the rock cycle.Learn more about Geology
The rock cycle explains the changes rocks undergo from the time they are expelled from the earth's mantle in the form of magma to the time that they return to the mantle and become magma once more. This process takes place over millions to billions of years, depending on the conditions the rocks are subject to. Weather, heat, water and pressure are all forces that affect the rock cycle.Full Answer >
When water combines with melted rocks in the magma chamber of the volcano, it pushes magma upward. Gas molecules form bubbles that expand as they rise. The pressure from the bubbles becomes stronger than the surface rock and it fractures, allowing the magma to reach the surface.Full Answer >
Granite and gabbro are igneous rocks formed through the cooling and crystallization of magma in the Earth's crust. They are identified by their specific mineral content and composition.Full Answer >
The specific type of rock that forms when magma cools at the Earth's surface is extrusive igneous rock. Igneous rock forms when magma cools, but where the magma cools determines the type of igneous rock that forms. Igneous rock gets its name from the Greek word for fire and is so called due to the extremely hot liquid from which the rocks originate.Full Answer >