Term 4 Exam Year 8 Semester 2

Question 1

What causes earthquakes?

Answer 1

Earthquakes are caused by the build up and release of stress within strata.

Question 2

What is elastic rebound?

Answer 2

As stress accumulates in ricks either side of the fault the rocks bend and distort until the earthquake occurs and the rocks snap back to their original state releasing energy that produces seismic waves.

Question 3

What is the epicentre?

Answer 3

The epicentre is the place in the earths surface where the earthquake is first felt.

Question 4

What is the focus?

Answer 4

The focus is the place inside the earth where the earthquake originates.

Question 5

What are seismic waves?

Answer 5

Seismic waves are energy released during an earthquake.

Question 6

What are the three different types of seismic waves?

Answer 6

P Wave - Primary Waves
S Wave - Secondary Waves
L Wave - Surface Waves

Question 7

What is a P Wave?

Answer 7

Primary Waves
Fastest
Compressional 
Weakest 
Travels through fluids and solids

Question 8

What is an S Wave?

Answer 8

Secondary Waves
Slower
Shearing (pulls rocks in opposite directions)
Stronger 
Only travels through solids

Question 9

What is an L Wave?

Answer 9

Surface waves
Slowest
Compressional and shearing
Strongest 
Travels through solids only

Question 10

What is the asthenosphere?

Answer 10

The layer of slow flowing hot semi-solid rock in the upper mantle.

Question 11

What is a seismograph?

Answer 11

A machine that records earthquake activity.

Question 12

What is a seismogram?

Answer 12

A record of earthquake activity.

Question 13

What are the different types of plate boundaries?

Answer 13

Transform
Divergent
Convergent (oceanic oceanic, continental continental and oceanic continental)

Question 14

What is a transform plate boundary?

Answer 14

When two plates slide against each other, these don’t make mountains or volcanoes but do produce lots of earthquakes. An example in real life is Los Angeles close to San Francisco (extra marks) where the North American plate is slowly moving downwards and the Pacific plate is slowly moving upwards, causing a transform boundary.

Question 15

What is a divergent plate boundary?

Answer 15

A divergent plate boundary is where two plates move away from each other causing constant creation of new land. Plates move apart and the crust expands. When two pieces of crust move away from each other, molten rock rises into the opening. An example of this in real life is Iceland because Iceland is constantly growing in size due to it being in the middle of the North American plate and the Eurasian plate.

Question 16

What is a convergent plate boundary?

Answer 16

A continental plate boundary is when two plates move toward each other?

Question 17

What are the three types of convergent plate boundaries?

Answer 17

Continental continental, when to continents converge
Oceanic oceanic, when two oceanic plates converge
Oceanic continental, when an oceanic plate and a continental converge

Question 18

What is a continental continental convergent plate boundary?

Answer 18

A continental continental plate boundary is when two continents meet head-on, the crust tends to buckle and be pushed upwards or sideways p. A real life example of this is the Himalayan mountains.

Question 19

What is an oceanic oceanic convergent plate boundary?

Answer 19

An oceanic oceanic convergent plate boundary is when two oceanic plates converge, one is usually subducted under the other and in the process a deep oceanic trench is formed. Oceanic oceanic plate convergence also results in the formation of undersea volcanoes. A real life example of this is Mid-Oceanic ridges or rift valleys. Such as Mt. Kilimanjaro, Dead Sea, Sea of Galilee.

Question 20

What is an oceanic continental convergent plate boundary?

Answer 20

An oceanic continental convergent plate boundary is when oceanic and continental plates move towards each other. When an oceanic plate pushes I to and subducts under a continental plate. Because it is more dense. The overriding continental plate is lifted up and a mountain range is created. A real life example of this is the Andes mountains.

Question 21

What is convection?

Answer 21

Convection is when particles rise because they are heating up, they then move across as they start to cool and fall once it has cooled down, this process continues. One the particles have reached the top they have nowhere else to go forcing the tectonic plates to move apart. This happens in the mantle.

Question 22

What is Sea floor spreading?

Answer 22

Sea floor spreading is when the old crust sinks down and new crust rises from the mantle to create new crust. This happens when the crust spreads out and new crust is formed.