The Rock Cycle & Igneous Rocks

Warm Up Videos

• http://youtu.be/lE3jR_RhxO4Types of Rocks Video

https://www.youtube.com/watch?v=iPqEbcMYBOoStudent videos

• http://youtu.be/PrN7jygu4cQ Igneous Rocks

The Rock Cycle • Scientists define rock as a naturally occurring mixture of one or

more minerals and organic matter. ROCKS ARE MADE OF MINERALS… and they are always changing.

• The rock cycle is the series of processes in which a rock forms, changes from one type to another, is destroyed, and forms again through geological processes.

Processes that Shape the Earth

• There are many ways that rock can be broken down and reshaped.

• Erosion – the process where wind, water, ice, or gravity transports soil and sediment from one location to another.

• Deposition – the process where material is laid down after transport.

• Rock pieces can be cemented and compacted together after weathering and erosion. This usually happens with sediment to form sedimentary rocks.

• Heat and pressure can turn igneous rocks and sedimentary rocks into metamorphic rocks.

• Too much heat can cause melting, which can turn any rock into magma. This would then cool to form an igneous rock.

Round and Round it goes… • As you can see, the rock cycle can just keep

going on and on. • We divide rocks into 3 main categories…

Igneous, Sedimentary, and Metamorphic. As you can see from the rock cycle, they form in different ways.

• The composition of a rock is the chemical make up (what its made of). This describes the types of minerals or other material in the rocks.

Where do igneous rocks come from?• Igneous Rocks form when hot, liquid

rock (magma or lava), cools and solidifies. The type of igneous rock depends on the magma composition and how long it takes to cool.

• Not all igneous rocks are made of the same minerals.

• FELSIC ROCKS - Light colored rocks are less dense. Consist of elements like Aluminum, potassium, sodium. Granite. Rhyolite.

• MAFIC ROCKS – Rich in calcium, iron, magnesium, and are darker in color. More dense than felsic rocks. Gabbro. Basalt.

• Intrusive Igneous Rocks – When magma pushes into surrounding rock below earth’s surface and cools slowly. Course grained texture, larger crystals.

• Extrusive Igneous Rocks – When magma erupts (lava) onto the Earth’s Surface. Cools quickly, very small or no crystals.

Types of Igneous Rocks

Below, you will see different parts of the volcano, and the intrusive bodies where igneous rocks can form.

Plutons are large and irregular-shaped intrusive bodies. Batholiths are the largest of the intrusive bodies. Dikes are sheet like intrusions that cut across previous rock units.Sills are sheet like intrusions that are parallel to previous rock units. Laccoliths are an intrusive body between two layers of sediment.