Plate Tectonics Flashcards
Crust
Earths outer shell
Made of 14 plates
Oceanic (5km thick)
Continental crust (30 to 70km thick)
Mantle
Essentially a solid but behaves like a liquid (semi-molten layer of rock) 1000C 2885km Magma here
Outer Core
Liquid metal is in motion
Mainly iron
2270km thick
4000C
Inner Core
Solid Metal Iron/Nickel 1216km 5000C - 7000C Heat source that drives convection
Asthenosphere
Soft plastic like rock
The upper mantle, just below the lithosphere
Lithosphere
The solid top layer of crust in which plates are formed
Consists of crust and upper mantle
Oceanic Crust Thickness
6-10km thick
Oceanic Crust Age
<200million years old
Oceanic Crust Density
Very Dense
3g/cm3
Oceanic Crust Mineral Content and Rock Type
Si Mg
Basalt
Which is denser oceanic or continental crust?
Oceanic
Continental Crust Thickness
30-70km
Continental Crust Age
1500 million - 3.8 billion years old
Continental Crust Density
Less dense than oceanic crust
2.7g/cm3
Continental Crust Mineral Content and Rock type
Si Al
Various Rocks, e.g granite
Convection currents
Draw and label a convection current’s diagram with arrows
Explain Earths heat source.
Heat is being produced through radioactive decay of naturally radioactive elements, eg uranium.
Subatomic particles are produced and collide with surrounding material inside Earth, motion equals heat
List 5 pieces of evidence supporting continental drift.
Fossil Fit Geological Fit Tectonic Fit Jigsaw Fit Paleomagnetism
Jigsaw fit example
Eastern South America and west Africa
Coastlines are matched at a depth of 1000m below sea level
How can gaps and overlaps in jigsaw fit be explained?
- Sea level rise
- coastal erosion
- Coastal deposition
- Land level changes
Geological Fit Example
Geology of eastern South America and west Africa were mapped and that ancient rock (2,000 million years old) were continuous from 1 continent to another
Tectonic Fit example
Fragments of an old fold mountain belt between 400 and 450 million years ago are found in a variety of continents
Caledonian Mountain In Greenland, England, Canada etc
Fossil Evidence
Fossils found on separate continents, (once connected)
They cannot swim or fly
How are paleomagnetism and continental drift linked?
New material @ mid oceanic ridge
Earths magnetism randomly flips
Striped pattern in magnetism and match it to age
Due to sea floor spreading
Slab Pull
@ subduction zones, gravity “pulls” the oceanic plate down into the mantle.
This destroys crust material
Ridge push
Material pushing out from the ridge
Sea Floor Spreading
Movement of oceanic crust away from constructive plate margins at mid-ocean ridges
Benioff Zone
Where plates melt in the mantle due to friction and heat
Constructive Margin
2 plates move apart leaving a gap in the middle or magma to rise from the asthenosphere and fill the gap
Constructive Margin Features
Shield Volcanoes - Eyjafallajokull
Earthquakes
Rift Valleys -East African Rift Valley
Mid-ocean Ridges - Mid-Atlantic Ridge
Destructive Margin
Dense oceanic plate descends beneath less dense continental plate
SUBDUCTION
Magma can rise through cracks in the continental plate and form volcanoes upon reaching the surface
Destructive Margin Features
Earthquakes
Volcanoes
Fold Mountains
Ocean Trenches
Conservative Margin
2 plates slide past each other along a fault line
Conservative Margin Features
Shallow Earthquakes
Fault line - San Andreas
Collision Boundary
2 plates of similar densities move towards each other causing the material between them to buckle upwards and form fold mountains.
Collision Boundary Examples
The Himalayas, (fold mountains)
Oceanic - Oceanic Margin
2 oceanic plates move towards each other
Faster/denser is subducted
Melts in Benioff zone
Less dense molten material arises
Oceanic - oceanic Margin Features
Ocean trenches - Mariana Trench Island arcs - West Indies Earthquakes Composite volcanoes - Montserrat Tsunamis
Oceanic - Continental Margin
Oceanic and continental Move towards each other
Denser oceanic subducts
Melts in Benioff Zone
Less dense molten material rises
Oceanic - continental Margin Features
Ocean trenches - Peru/Chile Trench
Composite volcanoes - Cotopaxi
Fold mountains – Himalayas
Continental- continental Margin
Continental plates move towards each other
Both plates have a lower density than asthenosphere
Can’t subduct
Collide and rise upwards
Continental - continental Margin Features
Earthquakes
Fold mountains – Himalayas
Hotspots
Small area with unusually high concentration of radioactive elements below the surface
Hotspot features
Shield volcanoes - Mauna Loa, Hawaii
Magma plume
Rising column of hot rock at plate margin or through a plate
