Earth's Structure And Plate Boundaries

Question 1

Name the earth’s layers (inner to outer)

Answer 1

Inner core, outer core, mantle, crust, asthenosphere, lithosphere

Question 2

Earth’s energy

Answer 2

• earth’s heat move continents, creates mountains & earthquakes
• a lot of heat is from when earth was created 4.5 billion years ago. when bombarding planetesimals stuck together.
• radioactive decay (eg of uranium) means more heat and seismic activity.
• seismic data shows core is between 5000-7000 degrees, 6350km deep

Question 3

Paleomagnetism

Answer 3

New material created at mid ocean ridge and takes magnetism of earth at that time. Earth’s magnetism randomly flips creating stripped pattern, can match to age. Possible due to ridge push

Question 4

Slab pull

Answer 4

At subduction zones gravity pulls ocean plate into mantle. This destroys crust material and keeps earth in shape

Question 5

Continental crust

Answer 5

Thicker than oceanic, about 40% of earth’s surface, most 1 billion years old but some 4 billion, less dense (approx 2.7/cm^3), SiAl, granite

Question 6

Oceanic crust

Answer 6

Thinner than continental, brand new-260 million years, denser (approx 3 g/cm^3), Sigma (Si,Mg), basalt

Question 7

Conservative boundary

Answer 7

Plates slide past each other along a fault, example is San Andreas Fault, only get powerful earthquakes

Question 8

Constructive boundary

Answer 8

2 plates are moving apart leaving a gap in the middle for magma to rise through, example is mid-Atlantic ridge and Iceland. Volcanoes, mid ocean ridges and rift valleys form here

Question 9

Destructive boundary

Answer 9

More dense oceanic plate descends below less dense continental plate, as plate descends it melts due to friction forming magma which rises through cracks in continental plate, example is where Pacific plate meets Eurasian in Japan. Powerful earthquakes, volcanoes, fold mountains and ocean ridges form here

Question 10

East African rift

Answer 10

Active continental rift zone, began developing 22-25 million years ago, a developing divergent constructive boundary where the African plate is splitting in two, rift extends 3000 km from Ethiopia to Mozambique with extension of 0.5 cm/ year, helps us to understand why continents break apart

Question 11

Rift valleys

Answer 11

On constructive margin plates move apart, crust warms as magma rises, due to convection currents the plates are thinned out, tension along faults occur and crackers appear allowing gas and steam eruptions, magma rises through cracks and erupts, horst (blocks squeezed up) and graben (blocks that descend)