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Adrian Clamonte
TA: 30
Lg 18 notes
Evidence of continental drift
* Continents were one joined together , but drifted
* Coast of continents can aligned
* Regions of some continents that are far apart have similar rocks, mountain ranges, fossils, patterns of pale glaciation
* Sea floor spreading provides a mechanism for continental drift
* Continents attached to tectonic plates (huge slabs of rock)
* Tectonic plates carry continents with them as they move across earth's surface
* Fossils matched
* Paleoglaciation : the extent of ancient glaciers and rock markings left behind
* Coal deposits in Antarctica
* Volcanoes and earthquakes caused by movement of tectonic plates
* Mid-atlantic ridge : a long mountain range running north to south down the Atlantic ocean
* Magnetic reversal : earth's magnetic can reverse
* Paleomagnetism: study of the magnetic properties of ancient rocks
* Sea floor spreading: convection current under earth's surface cause magma to rise, causing sea floor to spread apart
* Geological hot spot: area where molten rocks rises to earth's surface
Features of plate tectonics
* Layers: atmosphere, lithosphere
* Tectonic plates coverage = forming mountains
* Tectonic plates diverge = forming rifts on land, ridges in ocean
* Tectonic plates slides past at transform boundary building up pressure= earthquakes
* Tectonic plate boundaries / geological hot spots where magma is coming up the earth's crust = volcanoes
Tectonic plates
* Outer layer: several large plates
* Crust/ upper mantle: plates form lithospehere (12 major plates and many smaller ones)
* Oceanic plates contains dense rock basalt
* Continental plates contain granite
The crust
* Outer most layer
* Made from solid, brittle rock
* Thickness and type of rock varies in different parts of the crust
* Continental crust made from a lighter type of rock called granite and can be thick as 70 km
* Oceanic crust is made from a dense, dark rock called basalt and can be thick as 10 km
The mantle
* Earths thickest layer
* About 2900 km thick and it makes 70% of earth's volume
* 2 sections of mantle : upper and lower mantle
* Upper mantle is composed of partly molten rock containing iron and magnesium ; magma flows like thick toothpaste
* Transition zone separates upper mantle from lower mantle which begins a depth of about 660 km
* Lower mantle is made of solid, dense material that contains the elements magnesium and iron
The outer core
* The layer below the mantle
* About 2300 km thick
* Composed mainly mixture of iron and nickel
The inner core
* Earths centre
* Spehere with radius of about 1200 km
* Composed mainly iron and some nickel
* Temperatures at the core range from 5000 c to 6000 c
* Four times the melting point of iron
Plate motion
* Asthenosphere a partly molten layer in the upper mantle
* Geologists believe that this is because large quantities of radioactive elements such as uranium occur in some areas
* Convection current results as the hotter, and therefore less dense, material in the mantle rises, cools and then sinks again
* Mantle convection is one of the driving forces behind plate movement
Push and pull
* Rift valley rising currents of magma reach earth's surface at spreading centres on land (in ocean = spreading ridge/oceanic ridge)
* Ridge push = magma cools at surface becoming new rock, and new material at ridge, rift push old material aside moving tectonic plate away from the ridge
* Subduction: action of one plate pushing below another
* Subduction zones: experience earthquakes and volcanic eruptions
* Slab pull edge of tectonic plate subducts into mantle, pulling the rest of the plate with it
Plate interactions
* Plate boundary: region where 2 tectonic plates are in contract
* 3 types of plate interaction:
+ Divergence (spreading apart)
+ Convergence (moving together)
+ Transform (sliding by)
Divergent plate boundaries
* Mark the areas where tectonic plates are spreading apart
* Diverging plates: plates that are spreading apart
Convergent plate boundaries
* Where tectonic plates collide
* Converging plates: plates that are converging
Oceanic- plate convergence
* Cooling causes one plate to be denser, sliding deep into the mantle
* Produces long chain of volcanoes
* Force of collisions between oceanic and continental plates create mountain ranges when the continental rock crumples and folds
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