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Agenda Jan. 29, 2013 Mr. King 1. Rock Powerpoint – take notes 2. Assignment #15: Rock or Mineral Lab 3. Fossil Vocabulary 4. Homework: #19 Fossil Vocabulary Flash Cards ROCKS TYPES OF ROCKS AND THE ROCK CYCLE Rocks or Mineral? Rocks • No definite composition Minerals • Definite composition • Can have organic parts • Inorganic – • No definite properties • Definite properties • Classified by how formed • Classified by composition and crystal shape • no living remains TYPES OF ROCKS • Unlike minerals, rocks cannot be classified by their properties • Rocks are classified by HOW they formed TEXTURE tells the pressure & temperature; COMPOSITION tells where formed: Igneous: Melting & Cooling Sedimentary: Compacting & Cementing Metamorphic: Heat & Pressure IGNEOUS ROCKS Rocks that have been MELTED and COOLED • magma: molten rock below earth’s surface • lava: molten rock above earth’s surface IGNEOUS ROCKS MELTED & COOLED Classified by HOW FAST and WHERE they cool: • Intrusive rocks - cooled INSIDE the earth Cooling takes a LONG time because the earth insulates the heat; Slow cooling time means LARGE crystals • Extrusive rocks - cooled OUTSIDE the earth’s crust They are cooled quickly and form SMALL crystals IGNEOUS ROCKS MELTED & COOLED Granite Intrusive Large grains IGNEOUS ROCKS MELTED & COOLED Basalt* Extrusive Small grains *makes up new ocean floor Gases released near the surface of a lava flow create bubbles or that are “frozen” in stone IGNEOUS ROCKS MELTED & COOLED Pumice Extrusive - Small grains IGNEOUS ROCKS MELTED & COOLED Obsidian Extrusive Small grains - glassy Snowflake IGNEOUS ROCKS Summary HOT MAGMA When magma (melted rock) cools & crystallizes underground crystals grow large, and the rock is called GRANITE. When magma breaks through a weak part of the earth's crust the rock is called LAVA. Crystals are too small to see because volcanic rocks cool quickly. Examples: BASALT, SCORPIA, TUFF, PUMICE, and OBSIDIAN SEDIMENTARY ROCKS • Formed by COMPACTION & CEMENTATION • Composed of layers of sediments • Process : 1. Weathering: breaking down of rock at the Earth’s surface (mechanical or chemical) producing Sediments (rock fragments, sand, mud) 2. Erosion: transportation of weathered rock pieces 3. Deposition: eroded particles settle (often in layers) 4. Compaction: pressure applied squeezes out water 5. Cementation: fills in the gaps and “glues” rock SEDIMENTARY ROCKS COMPACTED & CEMENTED How to recognize sedimentary rocks: • Composed of various rock fragments • Composed of layers (strata) • Can contain fossils • Crumble easily SEDIMENTARY ROCKS COMPACTED & CEMENTED CONGLOMERATES form in stream beds and pebble beaches SEDIMENTARY ROCKS COMPACTED & CEMENTED SANDSTONE made up of fine-grained particles, has a sandy texture (feels gritty) Sandstones form in sandy environments such as beaches, sand bars, deltas and dunes SEDIMENTARY ROCKS COMPACTED & CEMENTED LIMESTONE – chemical weathering SEDIMENTARY ROCKS Summary Sedimentary Rocks, like sandstone, shale, & limestone are made from PIECES that were buried COMPRESSED) & CEMENTED together. METAMORPHIC ROCKS Rocks changed by heat and pressure • NO MELTING • Recrystallization: the crystals of old rock reform into new crystals and sometimes new minerals • Occurs below earth’s surface, usually between plates • Foliated (distinct layers of flatten minerals) vs. Nonfoliated (no layers) METAMORPHIC ROCKS PRESSURE & HEAT SLATE - foliated Parallel planes. Gray, black, green or red. Uses include roofing, fireplaces, and “blackboards”. METAMORPHIC ROCKS PRESSURE & HEAT GNEISS – foliated • Black and white banding • Banding is “squiggly” because heat makes the rock “plastic (flexible)” METAMORPHIC ROCKS Summary METAMORPHIC ROCKS have been CHANGED because of HEAT & PRESSURE Sedimentary Rocks Metamorphic Rocks Igneous Rocks THE ROCK CYCLE The Story of METACONGLOMERATE Conglomerate Once was a SEDAMENTARY conglomerate..... • It was subjected to high temperatures and pressure; • The pebbles squished and elongated to form layers (foliated) • Kept pebbly appearance • It became a metamorphosed conglomerate, and received a new name: metaconglomerate. THE ROCK CYCLE limestone The Story of Marble Once was a SEDAMENTARY limestone ..... • It was subjected to high temperatures and pressure; • The layers were flattened and twisted • It became a metamorphosed limestone, and received a new name: marble. • People polished it and used it in their homes as tiles. Some marble was even carved into statues! Metamorphosis of Shale to Gneiss From Sedimentary to Metamorphic SHALE is the most common sedimentary rock. Through pressure and heat, (metamorphism), it changes into other rocks. These changes take place without melting the rock! Shale Increasing Temperature and Pressure Slate Phyllite SHALE becomes SLATE Schist SLATE becomes PHYLLITE PHYLLITE becomes SCHIST SCHIST becomes GNEISS Gneiss Metamorphosis of Gneiss to Granite Gneiss When gneiss melts and cools, it becomes granite! Granite From Metamorphic to Igneous! THE ROCK CYCLE A model that sums up the formation, breakdown, and reformation of rock • Series of changes that “recycle” rocks from one type to another Assignment #15: Rock or Mineral Lab Fossil Vocabulary (p. 30) • Law of Superposition: Top layer is the youngest in undisturbed layers of rocks • Strata/Stratified/Stratification: Layer of rocks • Fossils: Remain or trace of living thing • Index Fossil: Fossil remains of organism that lived a very brief time – often found in only one layer of rock • Mass Extinction: Disappearance of large number of species over short time Fossil Vocabulary Cont. • Relative Time: Time compared to another time; younger or older than _____ • Resident Time: Time an element occupies a place • Absolute Time: Exact time – usually AD or BC are specified • Geologic Time Scale: Outline of major events in Earth’s history – based upon mass extinction periods Homework: #19 Fossil Vocabulary Flash Cards