6th Grade - Rocks

Rock

A solid mixture of minerals and other materials. Earth's crust is made of rocks.

Grains

The particles of minerals or other rocks that give a rock its texture.

Texture

The look and feel of a rock's surface, determined by the size, shape, and pattern of a rock's grains.

Igneous rock

A type of rock that forms from the freezing of molten rock at or below the surface.

Sedimentary rock

A type of rock that forms when particles from other rocks or the remains of plants and animals are pressed and cemented together.

Metamorphic rock

A type of rock that forms from an existing rock that is changed by heat, pressure, or chemical reactions. The heat and pressure can result from collisions between continental plates.

Extrusive Igneous rock

Igneous rock that forms when lava freezes on Earth's surface.

Intrusive Igneous rock

Igneous rock that forms from magma freezing beneath Earth's surface.

Sediment

Small, solid pieces of material that come from rocks or organisms.

Erosion

The process in which water or wind carries away fragments of rock.

Deposition

The process by which sediment settles out of the water or wind that is carrying it.

Compaction

The process by which sediments are pressed together under their own weight.

Cementation

The process by which dissolved minerals crystallize and glue particles of sediment together into one mass.

Clastic sedimentary rock

Sedimentary rock that forms when rock fragments are squeezed together under pressure.

Organic sedimentary rock

Sedimentary rock that forms from remains of organisms deposited in thick layers.

Chemical sedimentary rock

Sedimentary rock that forms when minerals crystallize from a solution.

Foliated metamorphic rock

Term used to describe metamorphic rocks that have grains arranged in parallel layers or bands.

Nonfoliated metamorphic rock

Metamorphic rock that doesn't have grains arranged in parallel layers or bands.

Rock cycle

A series of processes on the surface and inside Earth that slowly changes rocks from one kind to another.

Mineral Composition

Along with texture and color, geologists use this characteristic to help classify rock.

Breccia

Sedimentary rock made up of rock fragments with sharp edges.

Marble and slate

The two most useful metamorphic rocks.

Mantle

This is where the heat that changes a rock into metamorphic rocks comes from.

Heat and pressure

Deep beneath Earth's surface these can change rock into metamorphic rock.

Conglomerate

A sedimentary rock made up of rock fragments with rounded edges.

Size, shape, and pattern

These are used to describe a rock's texture which geologists use to determine a rock's grain.

Weathering

When heat, cold, rain, snow, freezing etc. break down rock into smaller pieces of rock.