Metamorphic rock

Coulter

Types of metamorphic rocks

0Heat and pressure deep beneath Earth’s surface can change any rock into metamorphic rock.

0Geologists classify metamorphic rocks according to the arrangement of the grains that make up the rocks.

Foliated rock

0Metamorphic rocks that have their grains arranged in parallel layers or bands.

0They split in layers.0Foliated rocks include: slate, schist, gneiss0Slate comes from heat and pressure changing the

sedimentary rock shale. Slate is a denser more compact version of shale.

Nonfoliated rocks

0The mineral grains in these rocks are arranged randomly.

0These do not split in layers.0Marble and quartzite are two metamorphic rocks that

are non-foliated.0Quartzite comes from sandstone. The quartz particles

recrystallize to form quartzite.

Rock cycle

0Forces deep inside Earth and at the surface produce a slow cycle that builds, destroys, and changes the rocks in the crust.

0 Is a series of processes on Earth’s surface and in the crust and mantle that slowly change rocks from one form to another.

Beginning

0 In the case of stone mountain, the rock cycle began millions of years ago.

0First a huge piece of granite formed underground. 0Then the mountain building slowly pushed the granite

upward. 0Over millions of years weathering and water began to

wear away the granite, forming sediment.

Continuing

0Over millions of years, layers of sandy sediment pile up on the ocean floor.

0Slowly the sand will compact by its own weight.0Dissolved calcite will cement the particles together.0Eventually that granite will form into sandstone, a

sedimentary rock.

Continuing

0More and more sediment will pile up on the sandstone. As it becomes buried pressure will increase.

0The rock will become hot.0Silica will replace the calcite holding the rock together

and the texture will change from gritty to smooth.0After millions of years the sandstone will change into

quartzite (metamorphic rock)

Rock cycle