Answer to Question 1
Igneous rocks crystallize from molten material called magma, which originates from melting rock within Earth. Magma may erupt at volcanoes, as lava and volcanic ash, or remain underground to solidify. There are two general kinds of igneous rocks. Volcanic rocks solidify at the surface whereas plutonic rocks solidify beneath the surface.
Sedimentary rocks form by deposition and precipitation of minerals grains that originated by the breakdown of older rocks under the conditions found in Earth's surface environment. Rocks of any kind, when exposed at Earth's surface, slowly deteriorate due to the processes of weathering. Physical weathering causes rocks to disintegrate into rock fragments or mineral grains. Chemical weathering involves reactions between minerals, the atmosphere, and water, which produce dissolved ions and new minerals.
Metamorphic rocks result from changes to preexisting rocks. These preexisting rocks may be sedimentary, igneous, or older metamorphic rocks. The changes typically occur at temperatures in excess of 200C, which distinguishes metamorphic rocks from the lower-temperature weathering and lithification processes that form sedimentary rocks. Importantly, however, the temperatures are not high enough to cause the rock to melt, which distinguishes metamorphic processes from those that form igneous rocks. A rock changes appearance when the minerals that compose it are changed or rearranged or both.
Answer to Question 2
A
The carbon cycle.
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