Hazards- Plate Tectonics

Question 1

What are the 3 types of Natural Hazard?

Answer 1

• Geophysical
• Atmospheric (hurricanes etc)
• Hydrological (unstable ground avalanches etc)

Question 2

What was Alfred Wegners Theory of Plate Tectonics?

Answer 2

• He discovered the jigsaw puzzle fit of the continents
• Was the first person to describe “Pangea” where the continents once made up one island by using Fossil Evidence to see how continents had drifted apart that once used to be joined
• Founded the theory of Continental Drift and how the tectonic plates have moved apart

Question 3

When and why was Wegners Theory finally accepted?

Answer 3

-Americans explored the ocean floor and discovered a Ridge of Volcanoes under the Atlantic. Further study shows that this is the Mid-Atlantic Ridge, the Earths Longest mountain range.

-Found that age of ocean floor increases either side of ridge, leading to “Sea Floor Spread”, that sea floor was created at a central point and has spread out.
Today new crust is formed at the ridge.

Question 4

What is the Continental Shelf?

Answer 4

A big drop off under the sea that is Continental Crust that has flooded.
Is around 250,000,000 years old

Question 5

What is Palaeomagnetism?

Answer 5

The study of the magnetic structure of the rocks.
As molten rocks cool down the ions in the rock are set, Positive Ions pointing out to the Magnetic Pole.
Today Positive Ions point North and Negative Ions point South.

Approximately every million years the Magnetic Poles switch.

Question 6

What other evidence is there to support the theory?

Answer 6

• Volcanoes and Earthquakes
• Ocean trenches
• Fold Mountains
• Oil in Antarctica and Coal in Sweden- used to be on the Equator
• Evidence of Glaciation in Southern India/ Northern Australia
• Limestone in the Dales

Question 7

Describe the structure of the Earth.

Draw a diagram.

Answer 7

Diagram must include:

• Upper Mantle
• Asthenosphere
• Inner Core
• Outer Core
• Mantle
• Mohorovicic Discontinuity (Moho)

Question 8

What do the Upper Mantle and Core form?

Answer 8

The Lithosphere

Question 9

Describe the Inner Core.

Answer 9

• Made up of Iron and Nickel in a solid dense state
• In excess of 6000c
• 1000 miles across

Question 10

Describe the Outer Core.

Answer 10

• Molten metals that are responsible for the Earths Magnetic Field
• In excess of 5000c
• 1130 miles thick

Question 11

Describe the Mantle.

Answer 11

• The largest layer by far
• Made of Less Dense Materials- Rock, Silicon and Oxygen etc
• 1420 miles thick
• Causes Convection Currents

Question 12

Describe the Asthenosphere.

Answer 12

• Semi molten state
• The section that continents move and float on
• 125 miles thick

Question 13

Describe the Upper Mantle.

Answer 13

• Is cooled and solidified to form a mesh with the crust known as the Lithosphere
• 30-60 miles thick
• Plates moving are actually the Lithospheric Plates

Question 14

Describe the Mohorovicic Discontinuity.

Answer 14

The divide/ transition between the Mantle and the Crust

-Where there is a Physical, Chemical and Structural Change

Question 15

What is Basalt?

Answer 15

Molten rock that comes directly from the Mantle.

Question 16

Name the 4 types of plate boundary.

Answer 16

• Oceanic Crust
• Continental Crust
• Destructive Boundary
• Collision Boundary

Question 17

What are Tensional Boundaries?

What are the two types of plate boundary that are Tensional?

Answer 17

Boundaries where there is a divergence of plates, they are pulling apart (constructive plate margins)

Oceanic Crust and Continental Crust

Question 18

What are Compressional Boundaries?

What are the two types of plate boundary that are Compressional?

Answer 18

Boundaries where there is a convergence of plates, plates are ,plates are moving towards each other.

Destructive Boundary and Collision Boundary