Plate movement

Plate movement

1. Earths Structure

   • Crust
     • Coldest layer of earths structure
     • Thinnest
     • 3 types of rock found are:
       • Metamorphic
       • Sedimentary
       • Igneous
     • different sections of crust
       • Oceanic
         • Basaltic
         • Least dense
         • 6-10km thick
         • constantly changing
       • Continental
         • Older than oceanic
         • approx. 70km thick
         • much denser
   • Mantle
     • convection currents
       • these currents are believed to be the reason why the plates move apart, together or to the side of one another
     • molten and liquid
     • estimated at 5000 degrees celsius
     • asthenosphere
       • The upper layer of the earth's mantle, below the lithosphere, in which there is relatively low resistance to plastic flow and convection is thought to occur.
     • Lithosphere
       • The rigid outer part of the earth, consisting of the crust and upper mantle.
   • Outer core
     • Liquid/semi-molten
   • inner core
     • Solid
     • estimated at 6000 degrees celsius
   • general
     • Earth is approx. 4.6 billion years old
     • the oldest rocks found are 3.8 billion years old
     • earliest Human remains are 2 million years old
     • earliest fossils of plants are 6 million years old

2. Plate Tectonic Theory

   • Palaeomagnitism
     • the branch of geophysics concerned with the magnetism in rocks that was induced by the earth's magnetic field at the time of their formation.
     • bands found on either side of the ocean
     • youngest rocks have been found near atlantic ridges and subduction zones
     • About every 400 thousand years polarity switches from north to south
     • magnetic surveys done in 195o
       • study magnetic force in rocks
     • magma has polarity
   • Alfred Wegener
     • suggested that land masses move apart
     • 1912
     • pangaea
   • Evidence
     • Biological
       • same animal fossil found on 2 different continents
         • The 'Measourus' was found on 2 different continents which were to far away to swim and it had no wings to fly and it couldn't have run there then swam as sell the distance is ,now, to far
       • Same plant fossils have been found on different continents
     • geological
       • the same rock type and age can be found in africa and south America
       • Glacial deposits
     • Climatological
       • different rocks
       • lime stone
       • Coal Deposits
         • They need tropical plants and conditions to be made yet we have coal under us
   • Frances Bacon
     • Suggested world was a jigsaw
     • 1620
   • Continental Drift
     • Radio Active decay releases heat creating convection currents
     • Always moving
       • Moves at the pace of a snail (approx)

3. Vulconicity

   • Lavas
     • Lahars
     • Basaltic
       • Known as basic Lava
       • found at spreading ridges
       • Material comes straight from the mantle
     • Andesitic
       • Destructive Margins
       • known as intermediate lava
     • Rhyolitic
       • Found at destructive and collision plate margins
       • Acid Lava
   • Minor extrusive features
     • fumeroles
       • superheated water turns to steam with sulfur
       • high sulfur content
       • sulphur turns the rock green
     • geysers/hot springs
       • super heated water heated by magma chamber or steam
       • escapes as hot water or steam
       • when pressure changes
       • can be active for long periods of time and in some places are predictable
     • solfataras
       • group of fumeroles
         • examples in the USA and Turkey
   • Intrusive features
     • Sills
       • horizontal layers running between layers of country rock
     • Dikes
       • runs against the layers/grain of the country rock
     • Batholiths
       • plume of magma slowly cooled under the surface
       • granite
     • Magma cools into igneous rock
   • Volcano Shape
     • composite
       • Andesitic lava (thick)
       • Explosive
       • made form layers of ash
       • most common on land
     • acid/dome
       • Explosive
       • Rhyolitic
       • steep sided
       • runny or thick and viscous lava
     • fissure
       • Basaltic lava
       • crack in crust volcanos e.g.; Iceland
       • runny lava
       • gentle/low viscosity
     • caldera
       • Andesitic lava
       • gases build up behind a blocked vent
       • Eg; Crater lake, USA
       • andesitic
     • shield
       • Thin Lava
       • Gentle slopping
       • Basaltic lava
       • Gentle explosion
       • Eg; Hawaii/ hotspots
       • vesuvius
   • Forms of Erruption
     • Icelandic
     • Hawaiian
     • Pelean
     • Plinian aka Vesuvian
     • krakatoan

4. Plate margins

   • Hotspots
     • eg; Hawaiian Islands
       • Island chains
       • in the middle of the pacific
         • doesn't sit on a plate boundary
     • Plumes of magma
       • weak part of the crust VS strong convection currents
     • thin lava
       • flat land
   • transform plate/ Conservative
     • only causes earthquakes (no volcanos)
       • no crust destroyed
         • 1 moving slightly faster that the other
     • aka slip margins
     • Eg: San Andres Fault line in California, USA
     • slide side by side
   • Divergent/Consructive
     • They Have Valleys
       • Rift valleys
       • Oceanic ridges
         • Submarine Volcanos
         • Eg; Iceland
       • cause both volcanos and Earthquakes
       • largest continuous up lift ridges
       • aka transform faults
   • Convergent/ Destructive
     • movement builds up friction
       • = Earthquakes
     • can have earthquakes and volcanos
     • It's when 2 plates meet
       • ocean - ocean
         • can give us Island archs
           • eg: Mariana Trench and japan
             • new land from material from the sea bed rises to the surface
         • Denser/ faster plate is subdected
       • ocean - land
       • land - land
         • Both rise up - fold mountains
           • eg; himalayas, Mt Everest
             • Isostatic Uplift
         • collision margins