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techtonics - Coggle Diagram

- - - - 4400c
      - less pressure-iron and nickle melts
      - liquid metal-grows 1mm a year as it solidifies
    - - hottest layer-6000c
      - solid iron and nickle-pressure locks molecules together
      - pressure + friction + radioactivity = heat produces
  - - - 220 +/- 30km depth
      - beneath continent
      - seismic waves-increase in velocity
    - - 2900km depth
      - sesismic waves-primary waves decrease and secondary waves disappear
    - - 8km depth - under oceans
      - 32km depth under continents
      - all waves accelerate
    - - a service which seismic waves change velocity
  - - - african
      - antartic
      - eurasian
      - pacific
      - indo-australian
      - south american
      - north american
    - - arabian
      - carribean
      - cocos
      - nazca
      - juan de fuca
      - phillippine
      - scotia
      - okhotsk
  - - - convection current pushes N American and Eurasian plates apart (ridge push)
        
        relapse of pressure on the rock in the gaps between plates causes it to partially melt > increase in volume > extrude through the gap
        
        extruded rock cools dow forming a ridge at Mid Atlantic ridge > occasionally breaks the surface of ocean > causes volcanoe
        
        cooled rock is compressed by the weight of the water above it > new ocean floor formed
        
        process continues so that newest ocean floor is closest to the ridge and oldest is furthest away
    - - mountain ridge found at plate margin as hot magma forces the crust to budge
        
        as plates move apart the brittle crust fractures > forms parallel faults
        
        areas of crust slowly subside between faults > form rift valley
  - - - slab pull is considered main driving mechanism
        
        stress caused by subduction is too great > contact gives way and crust snaps back into position > releases energy in the form of seismic waves that radiate out from the point the rocks give way
        
        energy travels through crust and the ground as surface shakes > often major earthquake is triggered
        
        as oceanic crust subducts it also starts to melt due to friction in Benioff zone > melting produces granite or andesitic magma that is viscous
        
        continental crust under strain > cracks appear > magma rises and is able to seep to surface causing volcanoes
        
        oceanic lithosphere descends > increase of pressure > puts plates under stress and strain > can cause the continental crust to fold under too
        
        1 more item...
    - - carribean volcanic island
      - 1975-volcano errupted
      - destructive meeting point of techtonic plates (subducting)
      - material comes through crust and causes lots of gas to be released-explosive volcano
      - hot acidic thick lava piles up at top of volcano and traps gas in a 'dome'
        
        1997 collapsed
      - acidic lava - rich in silica and stays liquid
      - pyroclastic flow - hot material moving at <1000km/hour
  - - - both plates have jagged edges so they do not smoothly pass each other > they are 'locked' together > stress on contact causes strain
        
        when stress is too great the plates jolt pass eachother > energy is released through sesimic waves
        
        s waves radiate from the focus > ground shakes and resultant earthquakes can be very high
    - - 12 Jan 2010 earthquake
        
        no warnings
      - 255,000 people died
      - 750,000 people injured
      - emergency aid from all over the world
      - shallow quake by margins and very powerful
      - plates jolt past and send shockwaves
      - strong seismic waves
  - - - 2005 Kashmir earthquake
        
        7.6 magnitude
    - - causes Mt Everist to rise by 2.5cm/year
    - - e.g. Tibetian Plateau
  - - - all continent were once joined together and were intact until 2000million years ago
      - fossil evidence- fossils found in each country far away from each other
      - mountains made from plates smashing together as the shape of continents fit perfectly together
      - Hess
        
        palaeomagnetism-the further away from the North Atlantic plate, the less magnesium in the ground due to seafloor spreading
  - - - hotspot spreads plume and causes stress on the crust > leads to cracking > mantle plume extrudes through crust > volcanos formed
        
        volcanoes are still active and the plate drags them over the hotspot
        
        as the volcano moves away from hotspot they become exstinct as there is no source of heat in the magma chamber
        
        waves erode volcanoes and the become sediments
  - - - Blackpool 2001 (2.2)
- - - - upwelling magma from plates moving apart
      - not explosve
      - steep stampa cones
      - gravel and viscous lava
    - - highly mobile, free flowing lava
      - lava moves away from erupting vent
      - cone with sloping sides
      - lava tubes
    - - stone ripples
      - lava tubes
      - hot bedrock and water
        
        hot springs
      - geezer-hot water blasted in the air
    - - when magma chamber emptied land fell and is now filled with water
      - rift valleys - depressions as techtonic plates slowly move apart
  - - - silica rich acidic lava
      - periods of inactivity
      - often highly explosive
    - - viscous lava stays at top of volcano and builds dome
      - builds and deforms from the inside
      - cools and solidifies when exposed
    - - creates pyroclastic flow - hot material flowing
      - vapourises and burns stuff in the way
    - - ash fall
      - pyroclastic flow
      - gets thicker
      - eroded away with rain
  - - - linear volcanic vent
      - flat shape
      - found on rift zones
      - usually no explosion
      - extend away from volcano summit
      - Iceland
      - Hawaii
    - - scoria - low density balsalt
      - conical shape
      - lava from expanding gas bubbles
      - Mauna Kea, Hawaii
    - - low angle profiles
      - lava flow of basaltic material
      - ground flow of lava that travel great distances
      - Mauna Loa, Hawaii
    - - conical shape
      - silica magma - sticky so builds up pressure
      - Krakatoa
  - - - gases exolve
    - - low visousity
      - iron rich - mantle
      - runny lava - balsalt
      - effusive
      - reduced silica
    - - high visoucity
      - viscous lava
      - more silica content - earths crust
      - explosive
      - gas is trapped = hard to exolve = explosive
    - - chemical properties of magma
      - viscousity of magma
      - behavoiur of gases
  - - - ash fall
      - lava flows
      - pyroclastic flows
      - toxic gasses
    - - volcanic landslides
      - lahars
      - jokulhlaups
  - - - divergent/constructive
      - melts due to lack of pressure from plates moving apart
      - gas exolves fast due to high tempratures
      - very frequent
      - balsalt rock
      - iron rich , low viscousity, runny lava
      - Iceland, Eyjalla Jokulls first phase
    - - convergent/destructive subduction zones
      - plates converge oceanic crust subducts and melts in Benioff zone
      - gas exolves slowly due to high viscousity of lava
      - infrequent
      - Rhiyolite with high sillicon dioxide
      - silica rich lava thats thick and acidic
      - Volcan del Fuego
    - - divergent/constructive
      - lack of pressure due to plates moving apart
      - gas exolves fast due to high temps
      - Balsalt rock
      - frequent
      - iron rich with low viscosity lava
      - Iceland, Eyjalla Jokulls second phase
- - - - new oceanic crust is created
      - EQ tend to be frequent small and low hazard risk
      - do not typically trigger tsunamis
    - - generate some of the largest and most damagging earthquakes
      - 2 plates moving towards eachother
      - megathrust faults-leading edge can lock under friction
      - locked fault can hold for hundreds of years building up enormous stress
      - elastic rebound theory
    - - plates slide past eachother
      - zone of friction occurs where plates move at different speeds
      - stress and strain
  - - - most damaging events have a sallow focus
  - - - cause ground to shake
      - geology can amplify seismic waves
      - magnitude of an EQ is related to the amount of movement in the fault
    - - water - saturated material temporarily loose strength and behave like a liquid
      - unconsolidated rock has pores that water can sit in
      - contact strengh lost when seismic wave occurs
    - - high hazard in mountainous areas
      - Nepal 2015