Rocks3 Main Types

What are ROCKS?

• A rock is a naturally occurring solid mixture of one or more minerals, or organic matter

• Rocks are classified by how they are formed, their composition, and texture

• Rocks change over time through the rock cycle

Three Major Types of Rocks

• Igneous

• Sedimentary

• Metamorphic

• Formed when magma (or lava) cools and hardens.

• Formed from particles of sand, shells, pebbles, and other fragments of material

• Form under the surface of the Earth from the change due to intense heat and pressure.

Some Characteristics to look for…

Crystals Small, flat surfaces that are shiny or sparkly, like tiny mirrors.

Fossils Imprints of leaves, shells, insects, or other items in the rock.

Gas bubbles "Holes," like Swiss cheese, in the rock.

Glassy surface A shiny and smooth surface, like colored glass.

Ribbonlike layers Straight or wavy stripes of different colors in the rock.

Sand or pebbles Individual stones, pebbles, or sand grains visible in the rock.

How Rocks Change…

• All rocks are constantly changing VERY SLOWLY from one type to another, again and again.

• Rocks change due to:– Heat and Pressure– Melting– Cooling– Weathering and Erosion– Compacting and Cementing

Heat and Pressure

Melting

CoolingLava Cooling

OR

Magma Cooling

Weathering and Erosion

Compacting and Cementing