Magma That Solidifies Below Ground Forms Geological Features Different From Those Formed At The Surface

Submitted By bethy213
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Magma that solidifies below ground forms geological features different from those formed by magma that cools at the surface.
Plutons- Most of Earth’s volcanism happens below the surface because not all magma emerges at the surface. Magma can force the overlying rock apart and enter the newly formed fissure. Magma can also cause blocks of rock to break off and sink into the magma, where the rocks will eventually melt. Magma can melt its way through the rock into which it intrudes. When magma cools slowly, it will crystallize. Over time, minerals in the magma solidify, forming intrusive igneous rock bodies. Some have ribbonlike features only a few cm thick and several hundred meters long. Others are massive and range in volume from about 1 km3 to hundreds of cubic kilometers. These are called Plutons, eventually reaching the Earth’s surface as a result of uplift and erosion. These are classified based on their size, shape, and relationship to the surrounding rock.
Batholiths and stocks-The largest Plutons are called batholiths which are irregularly shaped masses of coarse-grained igneous rocks that cover at least 100 km2 and take millions of years to form. Found in major mountain chains. Irregular shaped Plutons that are similar to batholiths but smaller are called stocks.
Laccoliths- Sometimes when magma intrudes into parallel rock layers close to Earth’s surface, some of the rocks bow upward. When the magma solidifies, a laccolith forms. Laccoliths are a lens shaped pulton with a round top and a flat bottom.
Sills- A sill forms when magma intrudes parallel to layers of rock. A sill can range from a few centimeters to hundreds of meters in thickness.
Palisades sill- The rock that was originally above the sill eroded. Because it takes great amounts of force to lift entire layers of rock, most sills from relatively close to the surface and some can metamorphose the surround rock.
Dikes- Dikes are pluton that cut across preexisting rocks. Dikes often form when magma invades cracks in surrounding rock bodies. Dikes range from a few