Plate Tectonics- Basics Flashcards
The inner core contains…
Nickel and iron
Name the earths structure from inner core to crust, and name whether each layer is solid, semi-molten, molten or rigid.
Inner core (solid) Outer core (semi-molten) Mantle (molten) Asthenosphere (semi-molten) Lithosphere (rigid mantle and crust)
The outer core contains…
Iron and nickel
Two types of crust…
Continental
Oceanic
Oceanic crust is… (thickness, density)
Thinner, 6-10km thick, but more dense
Continental crust is… (thickness, density)
Thicker, 30-70km, less dense
What is the lithosphere?
Rigid upper mantle between asthenosphere and crust.
What is the asthenosphere?
Semi-molten section of mantle.
Mantle contains…
Silicate rocks
The lithosphere is divided up into lots of sections called…
Tectonic plates
The plates move due to _ _ _ _ _ _ _ _ _ _ within the _ _ _ _ _ _ _ _ _ _ _ _ _
Convection currents
Asthenosphere
The place where two plates meet is called a…
Plate boundary or margin
Who came up with the Theory of Plate Tectonics?
Alfred Wegener
Alfred Wegener thought that…
The continents had drifted apart over millions of years from a Supercontinent called Pangaea.
What evidence did Wegener provide to support his theory?
The shapes of the East coast of South America and the West coast of Africa fit together.
Fossils, plant and rock types found on those coastlines suggesting they were once joined.
Why was Wegener’s theory disregarded by the geoscientific community?
He could not provide an explanation as to why the continents were drifting apart.
We obviously now know good old Alfred was barking up the right tree, and that convection within the mantle causes continental drift.
Where is new crust created?
When plates move apart- divergent or constructive boundaries
What is the name for when divergent (constructive) margins occur below water?
Sea-floor spreading
When did Alfred Wegener propose his theory?
1912
What did Bruce Heezen and Marie Tharp discover?
The mid-Atlantic ridge
Palaeomagnetism involves…
Mapping the magnetic fields of the earths surface.
How often do the earths poles switch/ reverse?
Every 200,000 years or so, the earth’s magnetic field reverses polarity (N and S switch)
What does Palaeomagnetism provide evidence for?
Sea floor spreading.
Example of constructive plate margin in the ocean…
Mid-Atlantic ridge
