Types of Rocks

1. Explain how rocks can be formed? 2. What is the rock cycle? Warm-Up:

Describe the texture and composition of the two igneous rocks. A B

How to Classify a Rock Rock - A naturally occurring, solid, mixture of one or more minerals or organic matter 3 Groups (based on formation): igneous, sedimentary, and metamorphic Texture and composition give clues as to how rocks are formed, and are used to classify rocks Composition – the type of material a rock contains Texture – the size, shape and arrangement of the minerals/particles that make up a rock. Rocks are always changing form in a cycle called the Rock Cycle

Web Links (also found on my website) Rock Cycle Interactive e/index.html Rock Cycle Animations rth_science/terc/content/investigations/e s0602/es0602page02.cfm

Igneous Rocks Extrusive rocks- formed by cooling lava Texture: glassy (obsidian) porous (pumice) fine-grained (basalt) Intrusive rocks- formed by cooling magma Texture: coarse-grained (granite)

Formation of Extrusive Igneous Rock

Extrusive Igneous Rock

Formation of Intrusive Igneous Rock

Intrusive Igneous Rock Yosemite N.P.

Obsidian…

Basalt…

Granite… Course Grained Texture

Pumice… Porous Texture

Sedimentary Rocks Formed by: Weathering (breaking down of rock) Erosion (movement of sediments) Deposition (collection of sediments) Compaction & Cementation

Examples of Weathering Mechanical Weathering Root Action Frost Action Moss

Examples of Weathering Chemical Weathering: Oxidation (rock exterior)

Five Agents of Erosion Gravity (Mass wasting) Wind Running water Glaciers Waves

Gravity (Mass Wasting) Slumping Soil creep

Wind

Running Water Yellowstone Canyon & River Niagara Falls

Glaciers

Waves Australia

Examples of Deposition Lateral moraine Cape Cod (spit) Nile River Delta

Compaction & Cementation

Sedimentary Rocks (categorized by composition) Clastic Rocks (rock fragments) Conglomerates (pebbles) Sandstones (sand) Shales (mud & clay) Organic Rocks (once living) Ex: limestone(coral and shells), coal (plants) Chemical Rocks (evaporation) Ex: rock salt, limestone, geodes, gypsum

Clastic Sedimentary Rock… Conglomerate Shale Sandstone

Organic Sedimentary Rocks… Coal (plant mateiral) Limestone (shell & coral)

Chemical Sedimentary Rocks… Limestone Gypsum rock Geode

Metamorphic Rocks Formed by tremendous heat & pressure, and chemical reactions inside the crust. Formed from all three rock types.

Types of Metamorphic Rock Foliated (bands or layers) Ex: schist, slate, gneiss Gneiss Slate

Unfoliated (no bands or layers) Ex: marble and quartzite Types of Metamorphic Rock Quartzite

Closure: Describe the texture and composition of the two igneous rocks. A B

Warm-up / Closure: 1. In igneous rocks how is cooling rate and crystal size related? 2. Which rock type would you have the best chance of finding a fossil? Why?