2.1 – Types of Rocks Objectives: • Define rock and describe what rocks are made of. • Know how to classify and describe rocks. • Explain how each of the three main rock types formed. • Describe the rock cycle.

What are Rocks? Naturally-formed, non-living earth material Collection of mineral grains (can be the same type of mineral grains or more than 1 type) Are the rocks in these pictures made from one type of mineral grain or several types? The different colors and textures seen in this rock are caused by the presence of different minerals. A pegmatite from South Dakota with crystals of lepidolite, tourmaline, and quartz (1 cm scale on the upper left). Rocks are made of minerals. The mineral grains in a rock may be so tiny that you can only see them with a microscope, or they may be as big as your fingernail or even your finger.

3 Main Types of Rocks Rocks are classified into 3 major groups according to how they form: Igneous Rocks Sedimentary Rocks Metamorphic Rocks

This diorite statue was made in approximately 2120 BC. Igneous Rocks Form when molten rock cools Make up most of the rocks on Earth Most are buried beneath sedimentary rock or ocean water Extrusive Igneous Rocks form from lava on Earth’s surface cool faster / form smaller crystals Intrusive Igneous Rocks form from magma beneath Earth’s surface cool slower / form larger crystals Uses: Buildings and Statues (ex. granite) Abrasives (ex. pumice) This diorite statue was made in approximately 2120 BC. This video discusses how to identify igneous rocks: http://www.youtube.com/watch?v=Q0XtLjE3siE .

Igneous Rocks Giant’s Causeway (hexagonal basalt formations) Northern Ireland (video)

Sedimentary Rocks form by the compaction and cementing together of sediments (broken pieces of rock-like gravel, sand, silt, or clay) that build up layer by layer May contain fossils of ancient organisms Uses: Construction - Buildings, Concrete, Asphalt The White House of the USA is made of a sedimentary rock called sandstone. Cliffs of Mohr, Ireland

Metamorphic Rocks form when the minerals in an existing rock are changed by heat or pressure within the Earth without melting. Uses: Building (ex. slate, marble) Art (ex. Marble) Toothpaste, plastics, paper = contain marble Pencil “lead” = graphite Quartzite is a metamorphic rock formed when quartz sandstone is exposed to heat and pressure within the Earth. This video discusses how to identify a metamorphic rocks: http://www.youtube.com/watch?v=qs9x_bTCiew .

Review: 3 Types of Rocks A simple explanation of the three rock types and how to identify them can be seen in this video: http://www.youtube.com/watch?v=tQUe9C40NEE . This Science Made Fun video discusses the conditions under which the three main rock types form : http://www.youtube.com/watch?v=G7AWGhQynTY (3:41).

The Rock Cycle Natural, never-ending cycle that changes the physical and chemical properties of rocks One type of rock is transformed into another type Takes place over millions of years

Annenberg Learner Interactives: The Rock Cycle http://www.learner.org/interactives/rockcycle/about.html

Processes of the Rock Cycle Crystallization Erosion and Sedimentation Metamorphism

Crystallization Crystals form at different temperatures as molten rock cool Rate of cooling determines size of crystals Slow cooling = large crystals Fast cooling = small crystals

Erosion and Sedimentation Weathering - wears rocks at the Earth’s surface down into smaller pieces called sediments. Erosion – transports sediments from one place to another via running water, ice, gravity, wind, etc. Sedimentation - sediments are laid down or deposited layer by layer.

Metamorphism Heat and pressure may cause the mineral composition and texture of rock to change