Earth

Question 1

List the layers of the Earth in order.

Answer 1

Crust, mantle, outer core and inner core.

Question 2

What is the Earths core made of?

Answer 2

Iron, nickel, alloy and some light elements.

Question 3

List the seven major tectonic plates.

Answer 3

• African plate
• Antarctic plate
• Eurasian plate
• Indo-Australian plate
• North American plate
• Pacific plate
• South American plate

Question 4

List the seven secondary tectonic plates.

Answer 4

• Arabian plate
• Caribbean plate
• Cocos plate
• Juan de Fuca plate
• Nazca plate
• Philippine plate
• Scotia plate

Question 5

List and define the 3 different types of tectonic plate boundaries.

Answer 5

Convergent- when plates are colliding into each other

Divergent- when the plates are moving apart from each other in opposite directions.

Transform- when plates are sliding parallel to each other but in opposite directions.

Question 6

Explain the process of sea floor spreading.

Answer 6

Magma rises up through mid ocean ridges in-between 2 plates (divergent boundary), cools rapidly and solidifies with the instant contact of the cool sea water, forming old oceanic crust. As the oceanic plates continue to move apart, more magma rises to fill the gap. This cycle continues and over time new crust forces the new oceanic crust further apart. This process results in seafloor spreading. At the end of the other plate where the oceanic plate meets a continental plate and collides. The oceanic plate is forced down (subduction) into the mantle and melts;it is recycled forming new magma.

Question 7

Explain the idea of continental drift.

Answer 7

Continental drift is the idea that all continents were once part of a super continent - Pangaea. This then split into 2 smaller continents - Gondwanaland consisting of what we now know as Africa, South America, Antarctica and Australia - Laurasia consisting of what we now know as Europe, Asia and North America. The idea also states that the continents are constantly moving.

Question 8

How was Harry Hess’ theory supported about sea floor spreading?

Answer 8

Frederick Vine and Drummond Matthews hypothesised the symmetrical pattern of stripes formed by the sea floor was no accident, but indicated that the Earth’s magnetic field switched direction over time, from its current direction to the opposite direction. When materials from the mantle rised up through mid ocean ridges, it cooled and conserved a record of the polarity of the Earth’s magnetic field. This is because magnetite in the basalts (which was in the magma from beneath the Earth’s surface) are of strong magnetics, and align themselves with the field when it cooled. Vine and Matthews noticed there was a symmetrical pattern of magnetic stripes on both sides of the mid ocean ridge, proving Harry Hess’ theory was relatively to almost certainly correct.

Question 9

What are the 2 types of the Earths crust and describe them?

Answer 9

Oceanic crust- the relatively thin part of the earth’s crust which underlies the ocean basins. It is geologically young compared with the continental crust and consists of basaltic rock overlain by sediments.

Continental crust- the relatively thick part of the earth’s crust which forms the large land masses. It is generally older and more complex than the oceanic crust.

Question 10

How are volcanos formed?

Answer 10

A plate boundary being subducted under another plate then eventually melts as it gets deeper in the mantle. The melted crust (then created magma) then bursts through a weakness in the Earths crust. More and more lava burst through this weak spot then solidifies and over time newer layers are added over the old, cool layers. This them creates a volcano.

Question 11

What materials come out of a volcano?

Answer 11

Ash, steam, lava, dust, projectiles, volcanic rock and gas.

Question 12

Why can lava be different viscosities?

Answer 12

Lava viscosity depends on how much silica in the lava. If the lava has high silica content, the lava would be very sticky and have high viscosity. If the lave has low silica content, it would be very runny and have low viscosity.

Question 13

Why are some volcanoes explosive?

Answer 13

Because gas in magma which is rich in silica (making it crucially viscous) build up in pressure and explode to release all this pressure.

Question 14

List the colour changes in lava as it cools.

Answer 14

Appears out of the volcano as bright orange, then as it cools it changes to bright red,then dark red, then brownish red and then when fully solidified it goes black.

Question 15

How fast and hot is a pyroclastic flow and what’s in them?

Answer 15

They can reach speeds up to 700 km/h and can reach temperatures of up to 1300*c. They consist of gases, ash, projectiles and volcanic rock.

Question 16

What are, where are and why do earthquakes happen?

Answer 16

Earthquakes result from movements in the Earths crust up to 700km below the surface. These movements cause vibrations or tremors on the Earths surface. Fortunately most of the tremors are too weak to be felt. When the tremors are sudden and stronger they are called earthquakes. They happen at or near plate boundaries when they are either pushing against each other in subduction zones, spreading apart to form ocean ridges or slipping and sliding against each other in sudden jolts. Tremors and minor earth quakes can take place wherever there is a weakness in the Earths crust, especially along fault lines. The epicentre of an earthquake is directly above the point below the surface where movement in the crust begins. The point at which the earthquake begins is called the focus.

Question 17

List and describe 3 types of waves that occur after an earthquake.

Answer 17

Primary waves (P-waves) - cause particles in rock to move back and forth in the same direction the wave is travelling.

Secondary waves (s-waves) - cause particles in rock to move at right angles to the direction of the wave travel.

Surface waves - move rock particles in a backward, rolling motion and a sideways swaying motion.