Rocks formation and cycle

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.Formation of rocks, Rock cycle, types of rocks. …

.Formation of rocks, Rock cycle, types of rocks.
Intended for Year 8 level - science

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  • 1. 3 types of rocksIgneous rocks - produced when magma from themantle cools and solidifies.Sedimentary rocks - formed by burial,compression, and chemical modification ofdeposited weathered rock debris or sediments atthe earths surface.Metamorphic rocks - created when existing rock ischemically or physically modified by intense heator pressure.
  • 2. •Where rocks come from.•Importance of rocks.•Types of rocks.•Formation of rocks.
  • 3. The crust is like a thin skin, with an average thickness of about 30 kilometres. Beneath the crust is themantle—about 3000 kmthick. It consists of solid rock, but under certain conditions it can bend and flow like a thick paste
  • 4. The crust and the top of the mantle is called thelithosphere which means ‘rocky sphere’.Below the lithosphere therocks are under immense pressure. They are veryhot, and in parts molten.This molten rock is called magma. It also contains dissolved gases.
  • 5. A rock is a solid substance that occurs naturallybecause of the effects of three basic geologicalprocesses; Magma Solidification; Sedimentation of weathered rock debris; Metamorphism.
  • 6. 3 types of rock formationsIgneous rocks - produced when magma from themantle cools and solidifies.Sedimentary rocks - formed by burial,compression, and chemical modification ofdeposited weathered rock debris or sediments atthe earths surface.Metamorphic rocks - created when existing rock ischemically or physically modified by intense heator pressure.
  • 7. Rocks can tell us many stories;Where the rock was formed;The general water depth (if marine or fresh water)The relative age of the rock (using fossils)Or it’s absolute age (if radioactive materials arepresent)Its original position and orientation on the surfaceof the earth
  • 8. Igneous rocks – 2 typesIntrusive (Plutonic) rock the magma has cooled andsolidified within the earths crustExtrusive (Volcanic) rock the magma cools andsolidifies on the earth’s surface.
  • 9. Rate of cooling & temperature changes determine thetexture & degree of crystallizationThe composition of the magma will determine thecomposition of the igneous rock
  • 10. Volcanoes form through weak spots in the earth’scrust.These may crack and allow magma to flow fromthe mantle to the surface.When this happens a volcano forms.The pressure inside the Earth pushes the magmaupwards. Sometimes the molten rock oozes outsteadily. At other times it blasts out with incredibleforce.Usually have no or small crystals
  • 11. Intrusive (Plutonic) rock the magma has cooledand solidified within the earths crust
  • 12. The longer Magma has to cool down thelarger the crystals will form in the rock.The size of the crystals demonstrates whereit came from
  • 13. What rock can float on water?C)AeroliteD)PumiceE)ChalkF)Eolianite
  • 14. Pumice is a type of lava full of gas bubbles. It canbe as light as Styrofoam, or nearly as dense asnormal rock.Aerolite is an old name for meteorites, andEolianite is any rock type that is made ofwindblown sediment. Chalk is a lightweight rock,but not that light.
  • 15. There are sometimes weak spots in the Earth’scrust that may crack and allow the magma to flowfrom the mantle to the surface. When this happensa volcano forms.The pressure inside the Earth pushes the magmaupwards. Sometimes the molten rock oozes outsteadily. At other times it blasts out with incredibleforce. Above ground = from lava (extrusive igneous rock) Usually have SMALL or NO crystals (they cooled too quickly)
  • 16. Basalt Granite1. Dark color 1. Light color2. High specific gravity 2. Low specific gravity3. Fine grained 3. Coarse grained4. Forms at the surface,principally in the ocean basins, 4. Forms on the continentsbut also in isolated "hot spots" deep undergroundon the continents.
  • 17. Why do we seeintrusive igneous rocks at the surface of the earth? 
  • 18.  Once a rock is formed, does it stay the same rock forever?
  • 19. 3 types of rocksIgneous rocks - produced when magma from themantle cools and solidifies.Sedimentary rocks - formed by burial,compression, and chemical modification ofdeposited weathered rock debris or sediments atthe earths surface.Metamorphic rocks - created when existing rock ischemically or physically modified by intense heator pressure.
  • 20. How many main types of Rocks are there?Igneous rocks are formed sediments?Rocks can break down from rain?The Majority of rocks found on the surface of theplanet are Metamorphic rocks.2 Types of Igneous Rocks are?How are extrusive (plutonic) rocks exposed?
  • 21. Igneous rocks – 2 typesIntrusive (Plutonic) rock the magma has cooled andsolidified within the earths crustExtrusive (Volcanic) rock the magma cools andsolidifies on the earth’s surface.
  • 22. Do you know the Rock Cycle?How are sedimentary rocks formed?What can sedimentary rock tell us?How are Metamorphic rock formed?What change occurs to the mineral grains when aSedimentary or Igneous rock changes tometamorphic rock?
  • 23. ormed from sedimentsrock fragments, mineral grains,animal & plant remains) thatare pressed or cementedtogether or when sedimentsprecipitate out of a solution.
  • 24. hese sediments are moved by wind, water, iceor gravity.edimentary rocks represent 7% of the Earth’scrust, but they cover 70% of the Earth’ssurface.edimentary rocks are
  • 25. As sedimentary rocks are deposited, theyform horizontal layers Scientists know thatthe layers on top (and the fossils in the top layer) are YOUNGER than the fossils in lower layers.
  • 26. ater or wind breaks down and deposits sediment(erosion & deposition)
  • 27. The heavy sediments press down on thelayers beneath (compaction)
  • 28. Dissolved minerals flow between the particlesand cement them together (cementation)
  • 29.  Clastic (also called Detrial)—made of broken pieces of other rocks
  • 30. Organic—remains of plants and animals are deposited in thick layers Examples Fossil rich limestone is made from the shells of ocean animals; used to make chalk
  • 31.  Chemical—minerals dissolved in lakes, seas, or underground water Mineral crystals are made as the shallow water that has flooded the bottom of Death Valley evaporates. Click on image for full size (66K JPG) Courtesy of Martin Miller, University of Oregon
  • 32. Examples Limestone made when calcite mineral precipitates from sea water Rock Salt— made from evaporation of sea waters
  • 33.  Rocks that have changed due to intense temperature and pressure Igneous, sedimentary and other metamorphic rocks can change to become metamorphic rocks Meta” means “change” andmorphosis means “form”in Greek
  • 34.  Places that are covered miles thick with other rock causing pressure Near colliding plates (near mountain ranges) Where magma intrudes relatively cool rock When hot water intrudes rock Where a meteorite strikes Earth (rare) Where lightning bolts strike rocks (rare)
  • 35.  Pressure from overlying rock layers High heat, but not enough to melt the rock Rocks may be flattened or bent or atoms may be exchanged to form new minerals.
  • 36. The minerals grains in rocks subjected to extreme pressure oftenrearrange themselves in a parallel fashion, creating a foliated texture(Image A - before metamorphism; Image B - after metamorphism).
  • 37.  Foliated—mineral grains are flattened and line up in parallel bands Example: gneiss formed from rearrangement of minerals in granite into bands
  • 38.  Non-Foliated—No bands are formed Example: marble formed from limestone
  • 39.  Write down what type of rock you think it might be. Based on what reason have you suggested what type of rock it is? Hint: Explain what features you observe for each rock Draw a simple picture of each rock No. Type of rock Rational Diagram 1 Sediment Has a grain appearance – looks like compressed grains 2 Igneous - Plutonic Has medium sized crystals. Coarse grained
  • 40. • No set path a rock takes to become another kind of rock
  • 41. http://www.classzone.com/books/earth_science/terc/content/investigations/es06
  • 42. IGNEOUS 1Weathering, Erosion, Compaction, Recrystallization Cementation Melting, Solidification Melting, Solidification RecrystallizationS E D 2M E N T A I 3 M E TA M O R P RY H IC Weathering, Erosion, Compaction, Cementation
  • 43. P226 – Q1, 2, 3, 5, 8P232 – Q1 – 12P240 – Q1 - 8
  • 44. Rocks are continually changed by many processes,such as weathering, erosion, compaction,cementation, melting, and cooling