* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download File
Survey
Document related concepts
Post-glacial rebound wikipedia , lookup
Physical oceanography wikipedia , lookup
Earth's magnetic field wikipedia , lookup
Age of the Earth wikipedia , lookup
Geochemistry wikipedia , lookup
Magnetotellurics wikipedia , lookup
Oceanic trench wikipedia , lookup
Abyssal plain wikipedia , lookup
History of geology wikipedia , lookup
History of geomagnetism wikipedia , lookup
Geomagnetic reversal wikipedia , lookup
Transcript
WELCOME TO PLANET EARTH ~4.6 BILLION YEARS OLD Inner Core: Solid inner core made up of Iron (Fe) and Nickel (Ni) • Solid due to tremendous pressure Outer Core: molten outer core made up of Iron (Fe) and Sulfur (S) • Semi-solid due to lower pressures Mantle: mostly solid rock • Upper area called Asthenosphere- slowly flowing rock Lithosphere: thin, rigid layer of rock • Outermost layer of the earth • CONTAINS rigid upper mantle and the crust- our solid surface of the earth. The Lithosphere floats atop the asthenosphere ---like a cracker on a layer of pudding. • Lithosphere moves and breaks into pieces called TECTONIC PLATES • ~dozen tectonic plates moving independently from one another • Earth sits on 6 giant plates, rest are under the ocean and continents. Two Types of Plates 1.Oceanic 2. Continental • Under oceans • Under continents • Thin • Thick • Dense and Heavy • Lighter • Always Sinks under • Never Sinks Plate boundaries: edges of the plates Places where two plates touch is where events like earthquakes, volcanoes, sea spreading, and mountains occurs 1.Convergent Boundary 2.Divergent Boundary 3.Transform Fault Boundary (or just transform) Divergent (sea floor spreading) Convergent (with subduction) Transform (San Andreas Fault) Boundaries Summarized Divergent Convergent (normal/constructive) (reverse/destructive) •plates are moving apart •plates are coming together Transform (strikeslip/conservative) •plates are slipping past each other •crust is not created or destroyed •new crust is created •Magma is coming to the surface • No volcanism •crust is returning to the mantle Divergent: Sea Floor Spreading • Mid Atlantic Ocean Ridge • longest topographic feature on Earth (70,000 km!) • 2-3 km above ocean basins Divergent: Sea Floor Spreading Pillow Lava Rocks under water, marine hotspot volcano chains and the constructive plate boundaries of mid-ocean ridges Transform Faults • Plates move past each other • strike slip faults Example: The San Andreas Fault California 3 Types of plate Collisions Oceanic Vs Continental Oceanic subducts or Sinks Continental Vs Continental No Subduction (mountain formed) Oceanic Vs Oceanic One will subducts or Sinks (heaviest) Convergent Plate Boundaries • Ocean-Continent collision • oceanic always subducts or sinks under continental Examples: Nazca plate vs. South American plate (forming the Andes) Convergent Plate Boundaries • Continent-Continent collision • No Subduction Example: Indian plate v.s. Eurasian plate (forming the Himalayas, Mt. Everest) Convergent Plate Boundaries • Ocean-Ocean collision • One of them always subducts or sinks Magma • molten material beneath the Earth’s crust. • collects in a magma chamber beneath a volcano, and can then be injected into cracks in rocks or issue out of volcanoes in eruptions. • temperature of magma ranges between 700 C and 1300 C. When it reaches the surface and comes out of a volcano, magma becomes Lava. So the different between magma and lava is location. Magma is deep underground, in chambers beneath volcanoes, and lava is the stuff that comes out of volcanoes. Post-Pangea movement is supported by evidence, including: 1.Palaeo-magnetism • When hot magma rises to the earth's surface and cools, the minerals themselves (especially magnetite) become magnetized in alignment with the Earth's magnetic field. 2.Palaeontology • Fossil evidence 3.Geological fit • continents seemed to fit together https://www.youtube.com/watch?v=yEYy_nVC4L0 Evidence that the Ocean Floor is Spreading • Magnetic Bands Reversals • • • • • Lava comes up along ridge lines (mostly underwater) as plates separate. In 76 million years there’ve been 171 reversals of the earth’s magnetic field. Lava contains iron. Cooling lava locks in the prevailing magnetism. The ocean floor near the ridges has the prevailing field and the floor further from the ridges shows field reversals: evidence that the ocean floor is spreading. • Rocks and fossils dating • Older as one moves away from ridges • Youngest rock is next to the ridge Earth's Magnetic Field (General) Magnetic field reversal • Proves the Earth magnetic field reverses itself every 27000 years • Another proof that the sea floors are spreading Age of sea floor as measured by fossils - Older as one moves away from ridges - Youngest rock is next to the ridge Hot Spot Formation of Hawaii The Pacific Ring Of Fire • A collection of earthquakes and volcanoes that make a ring around the Pacific ocean • It shows the inter-relation of plate tectonics