Tectonic processes and Hazards (EQ 1)

Question 1

Causes of Earthquakes

Answer 1

Earthquakes are primarily caused by the movement of Earth’s tectonic plates and the stress that accumulates along faults, volcanic activity and human activities can also contribute to seismic events.

Question 2

Causes of Volcanic eruptions

Answer 2

Volcanic eruptions are primarily caused by the movement of magma from the Earth’s mantle to the surface due to pressure build up and geological processes associated with tectonics plates.

Question 3

Causes of Tsunami’s

Answer 3

Tsunamis are primarily caused by the sudden displacement of a large volume of water, often resulting from underwater earthquakes, volcanic eruptions and landslides, the displacement of water sets off a series of powerful waves in both directions that can travel across entire ocean basins, posing significant threats to coastal areas.

Question 4

Global Distribution patterns of volcanos and earthquakes

Answer 4

Plate Boundaries: The majority of volcanoes are located along tectonic plate boundaries
Anomalies being from intraplate earthquakes and hotspots

Question 5

What are Convergent Plate Boundaries

Answer 5

Convergent boundaries occur where tectonic plates move toward each other. This motion results in the collision or subduction of plates, leading to intense geological activity.

Question 6

What are Divergent Plate Boundaries

Answer 6

Divergent boundaries occur where tectonic plates move away from each other. This motion is typically associated with the upwelling of material from the mantle, creating new crust.

Question 7

What are Conservative Plate Boundaries

Answer 7

Conservative boundaries occur where tectonic plates slide past each other horizontally. This lateral motion results in strike-slip faulting and seismic activity

Question 8

Distribution of Convergent Plate Boundaries

Answer 8

Commonly located around the edges of ocean basins there are 3 main types being : Ocean-ocean convergence , ocean-continent convergence and continent-continent convergence

Question 9

Distribution of Divergent Plate Boundaries

Answer 9

Divergent plate boundaries are often found along mid-ocean ridges, which are long underwater mountain ranges that traverse the ocean basins

Question 10

Causes of volcanoes associated with hot spots from mantle plumes

Answer 10

When one of the Earth’s plates moves over an unusually hot part of the Earth’s mantle. These hot areas are usually relatively stationary and result in large amounts of magma rising up, piercing a hole in the plate to form a volcano

Question 11

7 Factors that influence the severity of an earthquake on a place

Answer 11

• Tectonics and the global distribution of earthquakes
• earthquake magnitude and depth
• Population density
• Building and structural vulnerability
• Extent of earthquake awareness
• levels of development
• Governance

Question 12

How is the force of an earthquake measured

Answer 12

On the Richter scale

Question 13

How does the depth of the earthquake cause greater loss of property and life

Answer 13

Shallow earthquakes that occur close to the surface tend to result in a greater intensity of surface shaking and often cause the greatest loss of life and damage to property

Question 14

How do shallow earthquakes occur

Answer 14

Destructive margins where the subducting plate descends at a slight angle thereby creating stresses close to the surface.

Question 15

What is liquefaction and how does it exacerbate impacts of earthquakes

Answer 15

Some materials are vulnerable to becoming jelly-like when shaken, commonly associated with clays and silts. causing foundations of certain areas to become unstable and slopes become vulnerable to mass movement

Question 16

Explain why hotspots occur

Answer 16

An area on Earth over a mantle plume or an area under the rocky outer layer of Earth, called the crust, where magma is hotter than surrounding magma. The magma plume causes melting and thinning of the rocky crust and widespread volcanic activity.

Question 17

Evidence for continental drift

Answer 17

• Jigsaw fit
• Geological fit
• Tectonic fit
• Glacial deposits
• Fossil evidence

Question 18

What is isostatic change

Answer 18

• layers of ice weigh down plates during ice ages
• when the ice melts, the land rises again

Question 19

What is slab pull

Answer 19

Theory of plate tectonics which occurs at subduction zones. The thinner denser oceanic crust subducts below the thicker less dense continental crust. Convection currents move this crust, causing the subduction to become deeper. Gravity causes the subducted crust to be pulled down further and at a faster rate than the convection current

Question 20

What is ridge push

Answer 20

• Due to convection currents in the mantle, hot magma rises and at divergent boundaries along mid ocean ridges, the magma erupts through and cools, forming dense volcanoes. gravity acts on the volcanoes and pushes them down and away form the ridge causing the plates to move apart

Question 21

What is a tsunami

Answer 21

A series of waves, generated by a sudden displacement of water in the ocean.

Question 22

Why were the tsunamis from the Indian ocean in 2004 so devastating

Answer 22

-there is no early warning system for the Indian ocean unlike the pacific basin due to the infrequency of tsunamis here, unprepared.
-Earthquake its self was a 9.0 on the Richter scale
Island chains were low lying
-Densely populated
- Extremely poor countries were affected such as Indonesia and Sri Lanka

Question 23

How did the world respond to the 2004 disaster

Answer 23

Over £700 million had been committed for the recovery by foreign governments. £300 million in the first seven days
Emergency supplies being flown in

Question 24

How can the tsunami hazard be reduced?

Answer 24

-One is behavioural and relates to forecasting, warning and evacuation. Such an approach also encompasses land use management, public awareness and education.
- The other is structural and involves the building of structures to physically withstand tsunami and protect coastlines.

Question 25

Tsunami mitigation in Japan

Answer 25

• Dwelling houses to high ground
• Evacuation roads
• flood proof buildings
• Sea walls up to 10 metres high
• Offshore breakwaters

Question 26

Explain the global distribution of earthquakes

Answer 26

The global distribution of earthquakes is predominantly associated with tectonic plate boundaries, where the movement and interaction of Earth’s plates generate stress along faults and release it in the form of seismic events. However, intraplate earthquakes, hot spots, and human-induced seismicity can also contribute to earthquake activity around the world.

Question 27

Explain the causes of intra-plate earthquakes (4 marks)

Answer 27

The reactivation of ancient fault lines within a tectonic plate. These fault lines formed millions of years ago and since have become locked. Over time, stress accumulates along the faults due to movement of the earth’s interior, eventually leading to fault slippage and an intra plate earthquake.

Question 28

What is palaeomagnetism and sea floor spreading?

Answer 28

• Mid ocean ridges are formed when hot magma from the asthenosphere rises and forms new oceanic crust
• The new crust pushes the tectonic plates apart in a process called sea floor spreading
• Magnetic materials in the magma align themselves in the direction of the earths magnetic field, which cool and solidify once becoming crust
• Alternating magnetic stripes in the sea floor indicated that crust has formed at different times of polarity.
• Age of rocks mirrored either side of the mid ocean ridge