Earth’s History

1. Earth’s History

2. Slow Changes in earth’s crustal plates: mountain formation • Four different kinds of mountains: • Volcanic mountains – a.k.a. volcanoes (areas in which lava and magma move to the surface and burst through the crust). Way of releasing the planet’s internal heat. • Erosional mountains - formed by wind or water wearing down weak spots in land and carrying it away. • Fault-block mountains - formed by the vertical faulting of large blocks of earth. (Rocky Mountains) • Folded Mountains - formed by tectonic plates pushing against each other. Most common mountain. This causes immense pressure, and the only direction for these mountains to move is up.

3. Slow changes in Earth’s Crustal plates: ocean basins • The latest phase of ocean basin growth began with the breakup of the supercontinent Pangea (the landmass that existed when all continents were joined, from about 300 to 200 million years ago). • Involves subduction - a geologic process in which one edge of one crustal plate is forced below the edge of another. • Mostly all changes in ocean basins happen over millions of years. • Many parts of the ocean floor (such as the Pacific) is experiencing seafloor spreading (oceanic crust forms along the mid-ocean ridge system, and spreads out laterally away from them.)

4. Rapid changes in earth’s crustal plates: earthquakes • Earth’s surface = plates/tectonic plates (massive slabs of rock) • These plates are always moving. Sometimes they slide past one anotheror collide. • Plate movement causes the buildup of gigantic quantities of energy and when it’s released, it produces vibrations. • These vibrations produce earthquakes. • Faults, or giant cracks, are produced by the pressure.

5. Weathering • Weathering – mechanical and/or chemical breakdown of rock material that creates sediments at or near the surface of the Earth • 2 types of weathering: • Mechanical weathering - physical disintegration of a rock into smaller fragments. Also known as physical weathering. • Chemical weathering - process by which the internal structure of a mineral is altered by the addition or removal of elements. • Water initiates chemical weathering.

6. Erosion • Erosion – the incorporation and transportation of weathering products by a mobile agent such as wind, water, ice. • Forms of Erosion: • Running water/rivers • Wind • Wave currents • Gravity • Glaciers

7. Deposition of Sediments • Deposition – laying down of sediments at final erosion destination • Depositional environment – the type of location at which sediments are deposited. Depositional environment can be continental, coastal, or marine • 3 types of depositional environment: • Continental – deserts, lakes, stream beds, swamps, caves • Coastal – deltas, lagoons, sandbars • Marine – slope, ocean bottom

8. Rock formation • The Earth was formed about 4.6 billion years ago. • In that point of time, Earth was molten or liquid. • As the Earth cooled, the lightest materials floated to the top and the heaviest materials sank to the center. • The crust consists of the lightest rock.

9. Sedimentary rocks • Sedimentary rocks – rocks formed from existing sediments through lithification. (The processes by which loose sediment is hardened to rock.) • Pieces of Earth have eroded by braking down or warring away by elements like wind and water. • The pieces are washed downstream where they settle to the bottom of water sources. • Layer after layer of eroded earth is deposited on top of each. • The layers are pressed down with a lot of force. • As time passes, the process continues until the bottom layers slowly turn into a rock.

10. Igneous rocks • Formed either underground or above ground. • Underground- formed when the melted rock(magma)becomes trapped in small pockets. As magma cools slowly, it becomes igneous rocks. • Above ground - Also formed when volcanoes erupt. When the magma reaches the surface it is now call lava. The rock then forms when the lava cools. • Volcanoes are an example of a rapid change in Earth’s crustal plates because it is forming layers of crust quickly.

11. Metamorphic rocks • Have "morphed" into another kind of rock. • Could come from either Sedimentary or Igneous rocks • When rocks are under tons and tons of pressure, which creates heat to build up, and then forms the new rock. • Grains in these rocks appear flattened.

12. How fossils indicate earth’s movements • Since it is believed that the continents were once conjoined, fossils of species can be found on different continents because of the movement of the continents. • If the fossil of an animal that lives in a warm climate is found in a very cold region, it demonstrates how the animal’s remains have moved on the piece of the Earth to another region.

13. Questions • What change in the Earth’s surface creates ocean basins? (Click for answer.) • What types of rock have grains that appear to be flattened? (Click for answer.) Slow changes in the Earth’s crustal plates because the edge of one crustal plate is forced below the edge of another. (subduction.) Metamorphic rocks have grains that appear to be flattened because other kinds of rocks are forced together and they create layers.

14. Questions • How are underground igneous rocks formed? (Click for answer.) • What are 5 forms of erosion? (Click for answer.) Underground igneous rocks form when the melted rock becomes trapped in small pockets. As magma cools slowly, it becomes igneous rocks. Five forms of erosion are running water/rivers, wind, wave currents, gravity, and glaciers.

15. Sources • http://www.soils.wisc.edu/courses/SS325/weathering.htm • http://www.ux1.eiu.edu/~cfjps/1300/weathering.html • http://volcano.oregonstate.edu/vwdocs/vwlessons/lessons/Rocks/Rocks6.html • http://www.fi.edu/fellows/fellow1/oct98/create/ • http://itc.gsw.edu/faculty/bcarter/physgeol/sedrx/lith.htm • http://www.eduplace.com/kids/sla/6/volcanoes.html • http://external.oneonta.edu/hessf77/students/scottbliss/mountain.html#hamf • http://www.britannica.com/EBchecked/topic/424338/ocean-basin/285026/Evolution-of-the-ocean-basins-through-plate-movements • http://cartage.org.lb/en/themes/sciences/Paleontology/FossilsAndFossilisation/ProcessofFossilisation/Whatcanfossilstellus/Whatcanfossilstellus.htm