The Rock Cycle

A. Igneous Rocks

C. Metamorphic

B. Sedimentary

Melted rock cools and hardens underground or as lava

Higher pressures and temperatures cause rocks to melt

Higher pressures and temperatures

Weathering and Erosion

Sediments

Buried, compacted, and changed into rock

Higher pressures and temperatures

To the surfaceTo the surface

Igneous Rocks

• “From Fire”

• Made from molten rock

• This rock’s temperature is so hot that it melted.

www.usgs.gov

Igneous Rocks

• Two types of igneous rocks:– Rocks made from Magma (underground)– Rocks made from Lava (above ground)

www.windows.ucar.eduwww.usgs.gov

Intrusive Igneous Rocks• Intrusive igneous rocks are made underground

out of magma.• Since they are not ever exposed to air or water,

they cool very slowly. This allows minerals in the rocks time to form large crystals.

• These rocks are also called coarse grained rocks because they have large crystals.

• Most common intrusive igneous

rock is granite.

www.panet-terre.com

Extrusive Igneous Rocks• Made on the surface of the Earth out of lava.• These rocks cool quickly (small or no crystals).

Sometimes the lava cools so quickly that bubbles form from escaping gas. Some rocks are more than 50% holes!

• If the lava cools rapidly in water, the resulting rock can look like glass.

Obsidian Pumice

Sedimentary Rocks

• Rocks made from sediments that were either pressed together or cemented together.

• Most sedimentary rocks form under water.

www.earthsci.org

Sedimentary Rocks

• Layers of sediment compacted and cemented

www.usgs.gov

www.calstatela.eduSandstone

Limestone along the Katy Trail

Types of Sedimentary Rocks

• Clastic – composed only of rock fragments

• Organic – rocks that contain organic, or once material that was once living.

• Chemical rocks formed by a chemical process.

Clastic Sedimentary Rocks

• Rocks that are exposed at the surface of the Earth are subjected to weathering. This breaks the rocks into smaller pieces.

• The process of erosion then moves the pieces to another location where they are deposited.

• These pieces become compressed and cemented together to form a clastic sedimentary rock. The size of particles that make the rock is what identifies the rock type.

Non-Clastic Sedimentary Rocks• Organic – are made either directly or

indirectly from material that was once alive.

• Examples of materials that make up organic rocks are leaves and shells.

seis.natsci.csulb.edu

Non-Clastic Sedimentary Rocks Continued

• Chemical - Formed by a chemical process that do not involve living organisms.

• An example of these would be would be evaporites, which form when water evaporates out of a solution leaving the minerals behind.

• When the element Calcium (Ca) and the compound Carbonate (CO3) get dissolved in water, the water evaporates, the mineral Calcite (CaCO3) is left behind.

www.caverntours.com

Bonneville Salt Flats

When water containing sodium and chloride evaporates, the mineral Halite is left behind.

Metamorphic Rocks

• Meta- Change

• Morph- Form

• Metamorphic rocks are rocks that have changed form due to tremendous heat, great pressure, and chemical reactions.

• The mineral crystals in the rocks may change their size or shape, or become separated into layers.

Examples of Metamorphic Rocks

• Shale Slate

• Limestone Marble

• Sandstone Quartzite

Heat & Pressure

Heat & Pressure

Heat & Pressure

Foliated Metamorphic Rocks• Mineral crystals are arranged in parallel

bands. Rocks can break along these bands.

GneissSlate

Slate

Unfoliated Metamorphic Rocks

• Do not have bands of crystals and do not break into layers.

SerpentintiteMarble