How do the three main types of rocks form?

• How are rocks classified?

• What is the rock cycle?

Rocks and the Rock Cycle

• rock

• grain

• texture

• magma

Rocks and the Rock Cycle

• lava

• sediment

• rock cycle

• A rock is a natural, solid mixture of minerals or grains.

• Geologists call the fragments that make up a rock grains.

• Geologists use a grain’s size, shape, and chemical composition to classify rocks.

• Earth’s surface can cause rocks to break apart into many different-sized fragments.

Rocks

• The grain size and the way grains fit together in a rock are called texture.

• When a geologist classifies a rock by its texture, he or she looks at the size of minerals or grains in the rock, the arrangement of these grains, and the overall feel of the rock.

• Texture can be used to determine the environment in which a rock formed.

Rocks (cont.)

• The minerals orgrains in a rock help geologists classify its composition.

• Composition can be used to determine where a rock formed, such as inside a volcano or in a river.

Rocks (cont.)

Nancy Simmerman/Getty Images

Rocks (cont.)

How are rocks classified?

• The three major groups of rocks are igneous, sedimentary, and metamorphic rocks.

• When magma or lava cools and crystallizes, it creates igneous rock.

• Magma is molten or liquid rock underground.

• Lava is magma that erupts on Earth’s surface.

Three Major Rock Types

• Rock fragments, mineral crystals, or the remains of certain plants and animals, are the building blocks of sedimentary rocks.

• Sedimentary rocks form where sediment is deposited.

• Sediment is rock material that forms where rocks are broken down into smaller pieces or dissolved in water as rocks erode.

Three Major Rock Types (cont.)

Three Major Rock Types (cont.)

deposit

Science Use sediment or rock added to a landform

Common Use to put money in a bank

Sediment can be deposited in environments like rivers and streams, deserts, and valleys.

• Metamorphic rocks can form from any igneous or sedimentary rock or even another metamorphic rock.

• When rocks are exposed to extreme temperature and pressure, such as along plate boundaries, they can change to metamorphic rocks.

• Chemical fluids can also cause rocks to become metamorphic rocks.

Three Major Rock Types (cont.)

The series of processes that change one type of rock into another type of rock is called the rock cycle.

The Rock Cycle

• Forces on Earth’s surface and deep within Earth drive the rock cycle.

• On the surface, rocks can change due to natural processes, such as weathering, erosion, deposition, compaction, and cementation.

The Rock Cycle (cont.)

• Some rock cycle processes occur only beneath Earth’s surface, such as those that involve extreme temperature, pressure, and melting.

• Uplift is a tectonic process that forces these rocks onto Earth’s surface.

The Rock Cycle (cont.)

What is the rock cycle?

The Rock Cycle (cont.)

• Rocks are a natural solid mixture of minerals or grains.

• Texture describes the size and arrangement of minerals or grains in a rock.

Nancy S

imm

erman/G

etty Images

• The rock cycle represents a series of processes that change one rock type into another.

A. minerals

B. magma

C. igneous rock

D. grains

What do geologists call the fragments that make up a rock?

A. lava

B. sediment

C. metamorphic rock

D. magma

What is rock material that forms where rocks are broken down into smaller pieces by water erosion?

A. metamorphic rock

B. igneous rock

C. sedimentary rock

D. volcanic rock

When rocks are exposed to extreme temperature and pressure they can change into which of these?