Plate tectonics
Plates <ul><li>2 plates meet and push together </li></ul><ul><li>The continental plate folds upwards </li></ul><ul><li>The...
Evidence of Plate tectonics <ul><li>Jigsaw like fit of continents </li></ul><ul><li>Fossils found only in certain parts of...
Structure of Earth <ul><li>Solid Inner core- pressures so great its unable to melt even at extremely high temperatures. </...
How the plates move <ul><ul><li>Core is extremely hot </li></ul></ul><ul><ul><li>Upper mantle relatively cool </li></ul></...
Location of plate margins <ul><li>Location of volcanoes and earthquakes </li></ul><ul><li>Ocean trenches </li></ul><ul><li...
Fissure eruptions <ul><li>Occur where fissure in the earths crust dominate volcanic activity </li></ul><ul><li>Currents fr...
Conservative boundaries + Hot Spots <ul><li>Conservative boundaries  are formed when Plates move alongside each other and ...
Sea Floor Spreading <ul><li>Rising magma in mantle causes a bulge in the crust </li></ul><ul><li>The crust will eventually...
Case study – Mt St Helens May 18 th  1980 <ul><li>Buildings buried </li></ul><ul><li>More than 200 houses destroyed </li><...
Earthquakes <ul><li>3 types are: constructive (extensional), destructive (compressional) and conservative (transform) </li...
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Plate techtonics

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Plate techtonics

  1. 1. Plate tectonics
  2. 2. Plates <ul><li>2 plates meet and push together </li></ul><ul><li>The continental plate folds upwards </li></ul><ul><li>The oceanic plate sub ducts, this forms a deep ocean trench. </li></ul><ul><li>The 2 plates keep moving towards each other and this causes friction. </li></ul><ul><li>Friction causes heat which melts the plates </li></ul><ul><li>The magma created, forces its way out, causing the volcano to erupt </li></ul><ul><li>The force of the 2 plates rubbing against each other causes earthquakes. </li></ul><ul><li>Sea floor sediments are scrapped off and folded into mountain </li></ul>
  3. 3. Evidence of Plate tectonics <ul><li>Jigsaw like fit of continents </li></ul><ul><li>Fossils found only in certain parts of the world that are separated by sea, also with certain rock types and formations. </li></ul><ul><li>Glacial deposits is more tropical conditions </li></ul><ul><li>Coal deposits in colder countries (UK) </li></ul><ul><li>Long line of volcanoes down the mid-Atlantic ridge, suggesting movement of plates. </li></ul>
  4. 4. Structure of Earth <ul><li>Solid Inner core- pressures so great its unable to melt even at extremely high temperatures. </li></ul><ul><li>Liquid outer core – pressure slightly lower so is molten </li></ul><ul><li>Mantle – thickest layer, dense and mainly solid </li></ul><ul><li>Asthenosphere – Upper portion of mantle, molten, this allows plates to move </li></ul><ul><li>Lithosphere – the solid rocks of earths surface </li></ul><ul><li>Crust – tectonic plates. </li></ul>
  5. 5. How the plates move <ul><ul><li>Core is extremely hot </li></ul></ul><ul><ul><li>Upper mantle relatively cool </li></ul></ul><ul><ul><li>Hot material from mantle rises to surface </li></ul></ul><ul><ul><li>As material gets to top, it cools and sinks again. </li></ul></ul><ul><ul><li>This causes convection currents. </li></ul></ul><ul><ul><li>Some think the diverging currents cause the crust to split and diverge </li></ul></ul><ul><ul><li>Others believe that the sinking material drags the plate under, could be a combination </li></ul></ul>
  6. 6. Location of plate margins <ul><li>Location of volcanoes and earthquakes </li></ul><ul><li>Ocean trenches </li></ul><ul><li>Gravity anomalies </li></ul><ul><li>Active faults </li></ul>
  7. 7. Fissure eruptions <ul><li>Occur where fissure in the earths crust dominate volcanic activity </li></ul><ul><li>Currents from the mantle slowly push the 2 crusts apart, certain area’s split into a series of fissures </li></ul><ul><li>Fissures will then begin to erupt with 100m high of lava. </li></ul><ul><li>After several weeks eruptions stop, lava cools and seals up the fissures </li></ul><ul><li>A row of small cinder cones can be seen </li></ul>
  8. 8. Conservative boundaries + Hot Spots <ul><li>Conservative boundaries are formed when Plates move alongside each other and crust is neither created or destroyed </li></ul><ul><li>Evidence of this – a fault or contrasting geology either side of fault </li></ul><ul><li>Hotspots are a point in the middle of a plate where eruptions occur </li></ul>
  9. 9. Sea Floor Spreading <ul><li>Rising magma in mantle causes a bulge in the crust </li></ul><ul><li>The crust will eventually break due to the rising magma’s pressure </li></ul><ul><li>Magma will escape through faults in boundary </li></ul><ul><li>Magma cools quickly (as it is underwater) </li></ul>
  10. 10. Case study – Mt St Helens May 18 th 1980 <ul><li>Buildings buried </li></ul><ul><li>More than 200 houses destroyed </li></ul><ul><li>More than 185 miles of highway destroyed or damaged </li></ul><ul><li>Wildlife suffered – no home and death, salmon </li></ul><ul><li>Forrest damage – timber </li></ul><ul><li>Caused avalanche, mudflows and flooding </li></ul><ul><li>Crusting of ash helped grow crops in summer </li></ul><ul><li>Ash fall caused transportation problems – highways and roads closed, Airports shut due to lack of visibility </li></ul><ul><li>Ash caused pollution And damage to electrical systems many blackouts experienced </li></ul><ul><li>Unemployment rose in Mt St Helens region </li></ul><ul><li>Tourism down </li></ul>
  11. 11. Earthquakes <ul><li>3 types are: constructive (extensional), destructive (compressional) and conservative (transform) </li></ul><ul><li>Compressional cause the most damage </li></ul><ul><li>Quakes tend to occur in clusters, that strike the same area within a limited time period </li></ul><ul><li>Largest quake in the cluster is called the mainshock, those before are called foreshock and those after the aftershock </li></ul><ul><li>Undersea tremors can cause tidal waves (seismic sea waves or tsunami) </li></ul>

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