plate tectonics Flashcards
earth’s internal crust
crust
Mantle
Outer core
Inner core
Lithosphere
Earth’s crust and rigid upper mantle
Asthenosphere
it is in a molten state and the lower mantel and lithosphere float on top of it
describe the continental crust
Thick, averaging between 30 km and 70 km in thickness
Made up of light rocks, e.g. granite
Made from silica and alumina (SIAL)
MOHO line
the boundary between earth’s crust and the mantle
describe the oceanic crust
Thinner than the continental crust, averaging between
3 km and 10 km
Made up of heavy rocks,
e.g. basalt
Made from silica and magnesium (SIMA)
who came up with the idea of continental drift and when
Alfred Wegener 1912
what was the supercontinent called
Supercontinent Pangaea
what did the supercontinent split in
Laurasia and Gondwanaland
Proof of continental drift
Continental fit
Fossil distribution
Common rock types
Matching glacial deposits
when did pangaea split apart
200 million years ago
why is continental drift happening
The continents were fuelled by the convection currents and so they began to drift apart
who came up with the idea of seafloor spreading and when
Harry Hess 1960s
what is seafloor spreading
New rock is formed where plates were split apart
Ocean floor widens; magma rises from within the mantle and fills the opening
Magma cools; new ocean floor formed
New ocean floor is youngest at the mid-ocean ridge
Older crust moves away towards continents
There are three types of plate boundaries:
Divergent
Convergent
Transform
