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Earth and Life Science Week 3 - Rocks and the Rock Cycle.pdf
- 1. ROCKS AND THE ROCK CYCLE
- 2. PETROLOGY Scientific study of rocks
- 3. The Earth as a “rock” • The Earth is a solid rock with a depth of 2900 kilometers, where mantle meets the outer core
- 4. Rocks •Formed from aggregation of one or more minerals and other substances that are cohered into a solid structure.
- 5. Classification of Rocks Igneous Sedimentary Metamorphic
- 6. IGNEOUS ROCKS From the word “ignis/ignus” which means fire
- 7. Igneous Rocks Crystalline Formed from cooled magma or lava • Intrusive and Extrusive Rocks Pyroclastic Formed from consolidated eruption products like volcanic ash.
- 9. Extrusive/Volcanic rock • forms when magma makes its way to Earth’s surface • as lava and then cools. The crystals are very small (fine grained) since the cooling process is fast.
- 11. Extrusive Igneous Rocks •Glassy and fine texture due to the fast-cooling process, crystal formations are small and spread out
- 12. Intrusive/Plutonic FORMED FROM SLOWLY COOLED MAGMA FORMED BENEATH THE EARTH HAVE VERY LARGE CRYSTALS
- 13. Intrusive/Plutonic Rocks Gabbro and Granite This Photo by Unknown Author is licensed under CC BY This Photo by Unknown Author is licensed under CC BY
- 14. Pyroclastic Rocks • Formed on the surface, from consolidation of particle erupted by explosive volcanic activity This Photo by Unknown Author is licensed under CC BY
- 15. Color index of Igneous Rocks FELSIC COMPOSITION -light colors -rich in silica MAFIC COMPOSITION -dark colors -poor in silica but rich in iron and magnesium INTERMEDIATE COMPOSITION -have an intermediate color -gray or consisting of equal parts of dark and light mineral ULTRAMAFIC – very dark in color
- 17. Textures Phaneritic Phaneros-visible Crystals are visible to the eye without the aid of magnifying lens/Coarse grained Pegmatitic When minerals crystallize very slowly Composed of very large crystals (larger than 2 to 3 cm)
- 18. Aphanistic Aphaneros- invisible Fine grained, crystals cannot be distinguished without the use of magnifying tools Porphyritic Combination of fine and large crystals Glassy Non-ordered solid from rapid quenching
- 23. • For millions of years the earth’s surface have been broken down by wind, water, and other agents into smaller particles known as “sediments”
- 24. Sedimentary Rocks ⚫ Particles of sand, shells, pebbles, and other fragments of materials called sediments, accumulate in layers and over long period of time harden into rocks. ⚫ Compaction-due to increase of pressure of layered sediments it bind together to form the sedimentary rocks.
- 25. Formation of Sedimentary Rocks Erosion – wind, water and other agents carry away sediments Deposition – sediments are carried by bodies of water where they settle at the bottom Compaction – as more layers piled up the layers are smashed together therefore compacting it Lithification - complex process whereby freshly deposited loose grains of sediment are converted into rock. https://www.britannic a.com/science/lithificat ion
- 26. SEDIMENTARY ROCKS CLASTIC -from the cementation of sediments that have been deposited, buried, and compacted over a long period of time Examples: conglomerate, breccia, sandstone, shale CHEMICAL SEDIMENTARY ROCKS -from the precipitation of minerals from ion solutions Halite - formed when a body of seawater becomes closed off and evaporates. BIOCLASTIC/ORGANIC -from the compaction and cementation of plants/animal remains Coal - composed of organic matter in the form of plants fragments
- 29. Metamorphic rocks • These rocks are morphed or changed into a different type of rocks. Metamorphic means to change in form. It can be previously be igneous, sedimentary, or another metamorphic rock
- 30. Types of metamorphism Regional-due to changes in pressure and temperature over large region of the crust Contact-mainly by heat due to contact with magma
- 32. Classification: a. Texture - refers to the size arrangement ad grains within the rock. b. Foliation - any planar arrangement of mineral grains or structural features within the rock. *foliated - appeared banded or layered, contains crystals Example: mica • Non-foliated - made up of only few minerals
- 33. Foliated Metamorphic Rocks • Due to temperature and pressure minerals are aligned thus creating a banded appearance similar to pages of a book • Example-gneiss This Photo by Unknown Author is licensed under CC BY
- 34. Non-Foliated Metamorphic Rock • Do not show layers and are made up of only few minerals and shows almost a consistent appearance all throughout. • Example: Marble
- 35. Foliation will manifest physically in the rock’s tendency to separate along parallel planes. If minerals are barely visible to the naked eye, their alignment results in obvious but not clearly- defined foliation. If minerals are visible to the naked eye, their layering is more distinct. If the minerals are visible and elongated, the rock exhibit a coarsely- branded appearance due to alignment of minerals.
- 37. ROCK CYCLE -Model that describes all the processes by which rocks are formed, modified, transported, decomposed, melted and reformed.