ECGS Module 6A
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This document discusses the formation of rocks from minerals and their classification into three main groups: igneous, sedimentary, and metamorphic rocks. It describes how igneous rocks form from the cooling of magma, either deep underground or at the Earth's surface. Sedimentary rocks form from the compression of sediments and can contain fossils. Metamorphic rocks are formed from the alteration of existing igneous and sedimentary rocks through heat and pressure in the Earth. The document provides examples of common rock types in each category and their distinguishing features.
ECGS Module 6A
- 1. Exploring CCrreeaattiioonn wwiitthh GGeenneerraall SScciieennccee Foundations of Geology I Science is Organized Knowledge
- 2. What Are Rocks ? ...and Where Do They Come From?
- 3. Most rocks are formed from two or more minerals.
- 4. Minerals Minerals: naturally occurring, solid, inorganic substances with a definite chemical composition and an ordered internal structure. • Naturally occurring: not man-made, they can be found in nature • Solid: not liquid or gas at room temperature • Inorganic: not from living or dead organisms • Definite chemical composition: made from specific elements found in nature • Ordered internal structure: atoms arranged in a repeating patter
- 5. Minerals Some common minerals: • Halite (salt) - sodium and chloride • Calcite (antacid tablets) - calcium, carbon, & oxygen • Graphite (pencil lead) - carbon and clay • Rutile (white food pigment) - titanium and oxygen • Gypsum (drywall) - calcium, sulfur, oxygen & water • Talc (baby powder) - magnesium, silicon, oxygen & hydrogen
- 6. Rocks • Most rocks are a combination of minerals: • This rock, a granite pegmatite, is a mixture of mineral grains. – It contains pink orthoclase, milky quartz, black hornblende and black biotite.
- 7. Oddball Rocks • Some rocks don't fit the general description: – Coal is a rock made from organic materials. – Obsidian does not have a definite composition or ordered internal structure.
- 8. Experiment 6.1 Demo Alum Crystallization
- 9. • Inner core: SOLID iron-nickel alloy (750 miles across, 3,200 mi. deep) • Outer core: 1,400 miles of LIQUID iron and nickel
- 10. • Mantle: 2,220 miles of SEMI-SOLID rock (thick, molten magma) • Crust (lithosphere): 22 miles of SOLID rock (thinner on ocean floor)
- 11. Soil Layers • Rocks form the outer crust of Planet Earth. – Different types of soil lie above solid rock layers – Humus is nitrogen-rich soil made from the decaying remains of various organisms
- 12. Three Types of Rock • Igneous Rock • Sedimentary Rock • Metamorphic Rock
- 13. Igneous Rock • Igneous rocks form when molten lava or magma cools. • Color, density, & texture is determined by: – mineral composition – speed of crystallization
- 15. Igneous rocks: varied in texture, color & density. Scoria Granite Basalt Obsidian Pumice Gabbro
- 16. Sedimentary Rock • Sedimentary rocks form when pieces of rock or shell are deposited and pressed down under water, then cemented together by minerals in the water. • Texture and color determined by: – sediment size – mineral composition
- 18. Sedimentary rocks: soft, grainy or powdery, and may contain fossils. Breccia Sandstone Coal Limestone Flint Shale
- 19. Metamorphic Rock • Metamorphic rock forms when heat and pressure smash, fold, and transform igneous or sedimentary into a new (hard) type of rock. • Amount of heat and direction of pressure determines changes in the rock.
- 20. Metamorphic Rock Tectonic pressure causes: • Many thin layers (lamina) • Wavy/warped lamina • Flakes (foliation) • Usually deep below Earth's surface.
- 21. Metamorphic Crystalization • Crystals form in the spaces of sedimentary rock as liquid evaporates from a solution that contains a dissolved mineral. • Slow-growing crystals are larger than those that form quickly.
- 22. Metamorphic rocks: hard and may have thin layers (straight or wavy), shiny specks or sparkly crystals. Marble Amphibolite Gneiss Quartzite Schist Slate
- 23. Review: Major Rock Groups • Igneous – Formed from magma (molten rock) – Intrusive (plutonic): slowly cool underground – Extrusive (volcanic): quickly cool at the surface • Sedimentary – Form in layers at Earth’s surface, usually under water – May contain fossils • Metamorphic – Rocks changed by pressure and heat
- 24. WWhhaatt TTyyppee ooff RRoocckkss AArree TThheessee??
Editor's Notes
- #8: What is Coal? Coal is an organic sedimentary rock that forms from the accumulation and preservation of plant materials, usually in a swamp environment. Coal is a combustible rock and along with oil and natural gas it is one of the three most important fossil fuels. Coal has a wide range of uses; the most important use is for the generation of electricity.How Does Coal Form? Coal forms from the accumulation of plant debris, usually in a swamp environment. When plant debris dies and falls into the swamp the standing water of the swamp protects it from decay. Swamp waters are usually deficient in oxygen, which would react with the plant debris and cause it to decay. This lack of oxygen allows the plant debris to persist. In addition, insects and other organisms that might consume the plant debris on land do not survive well under water in an oxygen deficient environment. What is Obsidian? Obsidian is an igneous rock that forms when molten rock material cools so rapidly that atoms are unable to arrange themselves into a crystalline structure. It is an amorphous material known as a "mineraloid". The result is a volcanic glass with a smooth uniform texture that breaks with a conchoidal fracture. Where Does Obsidian Form? Obsidian is usually an extrusive rock - one that solidifies above Earth's surface. However, it can form in a variety of cooling environments: along the edges of a lava flow (extrusive), along the edges of a volcanic dome (extrusive), around the edges of a sill or a dike (intrusive), where lava contacts water (extrusive), where lava cools while airborne (extrusive)
- #10: Gravity: a result of Earth's MASS Magnetism: a result of the LIQUID outer core spinning around the SOLID iron inner core ~4,000 miles to center of Earth's core
- #11: Scale: 3,000 miles from Portland to Boston, 2,150 to Chicago, and 1,100 to San Diego
- #16: They may have tiny holes or a glassy surface, can be dense or frothy, or either solid-colored, streaked, or speckled.
- #25: Anybody know what type of rocks these are?