Chapter 6 Notes: Rocks

1. Chapter 6 Notes: Rocks Earth Science

2. 6.1 Objectives • Differentiate among the 3 major types of rocks. • Compare and contrast the processes in the rock cycle.

3. What is a rock? • A group of minerals bound together. • Consists largely of 1 mineral or of several different minerals in different quantities. • Igneous: formed from the cooling and hardening of hot, magma from inside Earth. • Sedimentary: formed from compaction and cementing of layers of sediment. • Metamorphic: formed by the effect of heat and pressure on other rocks.

4. The rock cycle • The repeated series of events that rocks change from 1 type to another.

5. The rock cycle 1. Magma is the source of all Earth’s rocks. 2. Cools when it reaches surface = igneous 3. Broken down by weathering forming sediments 4. Sediments compact and cement together = sedimentary 5. Gets buried under other sediments and exposed to high pressure and temp = metamorphic 6. Crustal movements force rocks deep into Earth, forming back into magma. 7. Rock cycle begins all over again

6. 6.2 Objectives • Distinguish between intrusive and extrusive igneous rocks and how they form.

7. Igneous rock formation • Intrusive: form from underground magma. • Form at Earth’s surface (volcanic ash). • Magma is felsic, mafic, or intermediate form: • Felsic: thick & slow moving. Large amounts of silica (SiO2). • Mafic: hotter, thinner, and more fluid. Higher amounts of iron, magnesium, and lower silica.

8. Igneous Rock formation cont. • Intrusive rocks = coarse grained texture b/c of longer cooling time. • Extrusive rocks = tiny crystals and fine grained texture. Can be smooth and glassy.

9. Igneous rock descriptions • Granite Family: form from felsic magmas • Coarse grained • Contain quartz, , feldspar, mica, and hornblende. • White, gray or pink color from feldspars • Intrusive • Obsidian, pumice, felsite, rhyolite

10. Igneous Rock Description cont. • Gabbro Family: Consists of mafic rocks. • Dark and denser than granite family rocks. • Contains pyroxene, olivine, plagioclase feldspar, biotite • Basalt is the most common rock.

11. Igneous Rock Descriptions Cont. • Diorite Family: has characteristics of both mafic and felsic. • Medium grays-green colors • Coarse grained member • Andesite

12. 6.3 Objectives • Distinguish among the 3 types of sedimentary rocks and how they form.

13. Sedimentary rocks • Covers most the Earth’s surface. • Classified by 3 basic formation processes. • Clastic rocks: Formed from fragments of other rocks due to weathering. • Fragments moved by H20 • Minerals fill in spaces between sand grains = cementation • Conglomerate: large fragments • Sandstone: small fragments, porous and permeable • Shale: smallest fragments, not porous or permeable

14. Sedimentary Rocks cont. • Chemical Rocks • RockFormed when minerals fall out of solutions (evaporation or chemical action). • Rock salt (halite), rock gypsum, limestones • Organic Rocks • Form from sediments made of plant & animal remains. • Limestone & coal (fossilized plants)

15. 6.4 Objectives • Explain the processes involved in the formation of metamorphic rocks.

16. Metamorphic rocks • Formed from preexisting rocks called parent rocks. • Metamorphism: the process where a rock’s structure is changed by pressure, heat, & moisture. • 2 types: regional & local

17. Metamorphic Rocks • Regional Metamorphism: Large areas of rock change form after exposure to intense heat & pressure. • Local metamorphism: 2 types contact & deformational • Contact: Hot magma moves into rock, heating it and changing it. • Causes fewer changes • Deformational: Occurs at low temps. & high pressure caused by stress & friction

18. Metamorphic rock descriptions • Foliation: the tendency of a rock to form bands of minerals or split along parallel layers. • Sandstone is the parent rock for quartzite. • Seashells formed by marine animals out of carbon and calcium ions form sedimentary rock limestone, which becomes marble.