1. 3 Types of Rocks December 9, 2015 7 th grade Chapter 9.3-9.5

2. Scientist of the Day

3. Rita Levi-Montalcini Wanted to be a writer; twin sister a painter Friend died of cancer – decided to be a doctor instead Lost job in WWII Italy because she was Jewish Started working in her bedroom, then as a refugee Discovered how nerves grow Won 1986 Nobel Prize in medicine

4. Rocks vs Minerals Rocks are usually mixtures of minerals and other components o Can be 1 mineral or several 4 main traits to classify rocks: 1.Mineral composition 2.Color 3.Texture 4.Origin

5. Rock Origins 3 major groups for rocks Determine rock group based on other properties Igneous rock: formed from cooling magma or lava Sedimentary rock: forms when particles of other rocks, plants, or animal remains are pressed and cemented together Metamorphic rock: when a rock is changed by heat, pressure, or chemical change, usually deep underground

6. Igneous Rocks Formed from magma or lava, which is high in silica When it forms below the crust, it’s called intrusive Above the crust, extrusive Trends (Not Always True): High in silica = dark rocks Low in silica = lighter-colored rocks When it cools quickly, it’s hard to form big crystals, so very fine grains in the texture. Hard, dense, and durable = good for arrowheads, countertops, fortresses

7. Sedimentary Rocks Sediment: small, solid particles of rocks or living things Sedimentary rocks form when sediment is deposited by water or wind and eventually stuck together Usually soft Sandstone and limestone are important building materials – sometimes used to make concrete too

8. Forming Sedimentary Rocks Weathering & Erosion DepositionCompactionCementation

9. 3 Types of Sedimentary Rocks Clastic rock: rock fragments are squeezed together. Classified according to how big the particles are. E.g. conglomerate, shale, sandstone Organic rock: formed when remains of plants or animals are pressed together. E.g. coal from swamp plants, limestone from shells & skeletons that are high in calcium Chemical rock: usually formed from solutions. E.g. Rock salt, limestone when it’s from evaporation

10. Metamorphic Rocks Start off as sedimentary or igneous rocks, then are changed by heat, pressure, chemical changes, or a combo of these processes. E.g. marble, slate Appearance, texture, and crystal structure of the minerals changes Classified by pattern of the grains Used as building materials, old blackboard, etc. Most metamorphic rocks are foliated Foliated: thin, flat layers in a rock