Igneous Rocks that are formed from melted rocks Magma or lava cools There are two types of igneous rock

Intrusive- Igneous rocks that cooled and formed underground. 2 Types of Igneous Rocks Extrusive- Igneous rocks that cooled and formed above ground. Intrusive- Igneous rocks that cooled and formed underground.

Intrusive Igneous Rocks Cool slowly, underground. Slow cooling = LARGE crystals Crystals are visible to eye Example: Granite, Diorite

Extrusive Igneous Rocks Lava cools quickly on surface. Microscopic crystals= FAST cooling Often looks like glass Example: Obsidian

Extrusive Lava often cools quickly, trapping air bubbles (vacuoles) in the rock. These air bubbles make the rock feel very light. Example: Pumice

Sedimentary Rocks that are formed from pieces of rocks or organic matter. Compacted and cemented together.

Types of Sedimentary Clastic – sedimentary rocks from deposition of rock particles Biochemical – sedimentary rocks from deposition of organic matter

Fossils If the sample contains fossils, it must be sedimentary. Only sedimentary rocks have fossils.

Sometimes layered Grains can be large (coarse) or small (fine) Cemented Grains Sometimes layered Grains can be large (coarse) or small (fine)

Examples Coquina - Small shells cemented together. Layered Sandstone Conglomerate – meaning all different sizes Shale or slate

Rocks that have been changed by heat and/or pressure. Metamorphic Rocks that have been changed by heat and/or pressure.

Common Metamorphic Rocks Limestone becomes Marble Shale and Slate become Schist Sandstone becomes Quartzite Granite becomes Gneiss

How do metamorphic rocks form? The parent rock can be “cooked” by a nearby magma intrusion. Called contact metamorphism. High pressure from rocks crashing together at convergent plate boundaries.

What clues do I look for? Foliated – metamorphic rocks that are layered Crystals squeeze flat and connect into a banding pattern

Nonfoliated – metamorphic rocks that are not layered What clues do I look for? Nonfoliated – metamorphic rocks that are not layered

The Rock Cycle

What you will learn… What are the 3 types of rocks? How are each formed? What clues do they give about their formation? How can I use physical characteristics to identify them?

How is this a cycle ? The rocks are constantly being recycled. Almost all of the Earth’s crust has been recycled (re-melted and began again as igneous rocks)