Unit 3 - Rocks (2017/2018)
- 1. Rocks Unit 3
- 2. 2.1 The Rock Cycle •Rocks – a naturally occurring solid collection of one or more minerals. •Three Major Types of Rock • Igneous Rock • Sedimentary Rock • Metamorphic Rock
- 3. 2.1 The Rock Cycle •Igneous Rock – rocks that forms when magma cools and solidifies.
- 4. 2.1 The Rock Cycle •Sedimentary Rock – rocks formed by the compaction and cementation of sediments.
- 5. 2.1 The Rock Cycle •Metamorphic Rock – rocks formed when existing rock is changed by heat and/or pressure.
- 6. 2.1 The Rock Cycle •Rock Cycle – shows the processes in which rocks form, are destroyed, and form again.
- 7. 2.1 The Rock Cycle •Much of the rock in Earth’s crust has passed through the rock cycle many times, but some rock does not pass through each stage in the rock cycle.
- 8. 2.2 Igneous Rocks •Igneous Rock – rocks that forms when magma or lava cools and solidifies.
- 9. 2.2 Igneous Rocks •Identity of an igneous rock is determined by… • the chemical composition of minerals in the rock. • Felsic = rich in feldspar and silica = lighter color • Mafic = rich in magnesium and iron = darker color • the rock’s texture. • Fine grained • Coarse grained
- 10. 2.2 Igneous Rocks •Magma forms when rock melts. •Three factors that cause a rock to melt. • Temperature • Pressure • Presence of fluids in the rock
- 11. 2.2 Igneous Rocks •Igneous rocks are classified according to where the magma cools and hardens. • Intrusive Igneous Rock • Extrusive Igneous Rock
- 12. 2.2 Igneous Rocks •Intrusive Igneous Rock – rock that cools deep inside the crust.
- 13. 2.2 Igneous Rocks •Extrusive Igneous Rock – lava that cools at Earth’s surface.
- 14. 2.2 Igneous Rocks •Igneous rocks are also classified according to the texture and crystal size.
- 15. 2.2 Igneous Rocks •Course Grained Texture • Intrusive igneous rocks normally have large crystals because they cool very slowly within the Earth. • Granite
- 16. 2.2 Igneous Rocks •Fine Grained Texture • Extrusive igneous rocks normally have small mineral grains too small to see. • Basalt, Rhyolite
- 17. 2.2 Igneous Rocks •Porphyritic Texture • Both large and small crystals • Diorite, Porphyritic Granite
- 18. 2.2 Igneous Rocks •Glassy Texture • When magma cools quickly few crystals are able to grow and a glassy texture forms. • Obsidian
- 19. 2.2 Igneous Rocks •Vesicular (Porous) Texture • If there are a lot of dissolved gases in the magma and the magma cools rapidly this can produce a rock full of holes, or vesicles. • Scoria, Pumice
- 21. 2.3 Sedimentary Rocks •Sedimentary Rock – rocks formed by the compaction and cementation of sediments.
- 22. 2.3 Sedimentary Rocks •Sediments – loose fragments of rock, minerals and organic material that result from the breakdown of rock by weathering.
- 23. 2.3 Sedimentary Rocks •Processes that convert loose sediment to sedimentary rock… • Weathering • Erosion
- 24. 2.3 Sedimentary Rocks •Weathering – when wind and water break rock down into smaller pieces, or sediment.
- 25. 2.3 Sedimentary Rocks •Erosion – the movement of sediments by wind, water, gravity, or other natural forces.
- 26. 2.3 Sedimentary Rocks •Deposition – the depositing and accumulation of sediment in an area.
- 27. 2.3 Sedimentary Rocks •Compaction – the process in which sediment is squeezed and the space in between grains is reduced by the weight of the overlying layers.
- 28. 2.3 Sedimentary Rocks •Cementation – the process in which sediments are glued together by minerals as water evaporates.
- 29. 2.3 Sedimentary Rocks •Types of sedimentary rocks are determined by processes in which the rocks form and their composition. • Chemical Sedimentary Rock (CSR) • Organic Sedimentary Rock (OSR) • Clastic Sedimentary Rock (CSR)
- 30. 2.3 Sedimentary Rocks •Chemical Sedimentary Rock (CSR) – forms from minerals that were dissolved in water and as water evaporates minerals are left behind. • rock salt, gypsum, dolomitic limestone, stalactites, and stalagmites
- 31. 2.3 Sedimentary Rocks •Organic Sedimentary Rock (OSR) – forms from the remains of living things. • coal, chalk, and shell limestone Coquina, made with shells
- 32. 2.3 Sedimentary Rocks •Clastic Sedimentary Rock (CSR) – formed by rock fragments that are carried away from their source by water, wind, and ice and are compressed and glued together by minerals. • Groups of CSR based on the size of the sediments • Conglomerates: large grains • Sandstones: sand sized grains • Shales: fine grained
- 36. 2.4 Metamorphic Rocks •Metamorphic Rock – rocks formed when existing rock is changed by heat and/or pressure. •Metamorphism – the process in which heat, pressure, and chemical processes change existing rock.
- 37. 2.4 Metamorphic Rocks •Types of Metamorphism • Contact Metamorphism • Regional Metamorphism
- 38. 2.4 Metamorphic Rocks •Contact Metamorphism – a change in the texture, structure, or chemical composition of a rock due to contact with magma. • Only a small area of rock is changed by the heat. • Often occurs near volcanoes.
- 39. 2.4 Metamorphic Rocks • Regional Metamorphism – a change in the texture, structure, or chemical composition or a rock due to changes in temperature and pressure over a large area. • Large area of rock is changed. • Result of tectonic movement.
- 40. 2.4 Metamorphic Rocks •Metamorphic Rock Classification • Foliated Rocks • Nonfoliated Rocks
- 41. 2.4 Metamorphic Rocks •Foliated Rocks – occurs when rocks are arranged into bands under great pressure and some heat. • Slate, Schist, Gneiss
- 42. 2.4 Metamorphic Rocks •Nonfoliated Rocks – rocks that do not have bands because they formed under little pressure and great heat. • Rock does not melt • Marble