Tectonics Lesson 1: Global Distribution

Question 1

Define intra-plate earthquakes

Answer 1

Occur in the middle or interior of tectonic plates. Much rarer than boundary earthquakes e.g. Church Stratton, Shropshire

Question 2

Define volcano

Answer 2

Landforms that develop around a weakness in the Earth’s crust from which molten magma, volcanic rock and gases are ejected and extruded

Question 3

Define seismic hazards

Answer 3

Generated when rocks within 700km of the Earth’s surface come under stress that they break and become displaced

Question 4

Define tectonic hazards

Answer 4

Includes earthquakes and volcanic eruptions, as well as secondary hazards like tsunamis and represent a significant risk in some parts of the world in terms of loss of life, livelihoods and economic impact

Question 5

% of earthquakes found on Pacific Ring of Fire

Answer 5

70%

Question 6

% earthquakes found on plate boundaries

Answer 6

95%

Question 7

Where are earthquakes distributed?

Answer 7

1) Oceanic fracture zone - found along mid ocean ridges
2) Continental fracture zone - found in mountain ranges
3) Scattered earthquakes in continental interiors / intra-plate earthquakes

Question 8

Example of oceanic fracture zone

Answer 8

Mid-Atlantic Ridge

Question 9

Example of continental fracture zone

Answer 9

Himalayas

Question 10

Example of intra-plate

Answer 10

Church Stretton, Shropshire

Question 11

How are volcanoes distributed?

Answer 11

Mainly along plate boundaries, but the type of plate boundary can determine whether a volcano exists
Some found away from plate boundaries in areas called hot spots

Question 12

How many active volcanoes are there?

Answer 12

500

Question 13

How many volcanoes erupt each year?

Answer 13

50

Question 14

What determines the violence of a volcano?

Answer 14

Amount of dissolved gases in the magma and how easily the gases escape

Question 15

What causes intra-plate earthqaukes?

Answer 15

1) stress building in ancient fault lines - become active again
2) fracking - stress caused by human activities - active again

Question 16

What are hot spot volcanoes?

Answer 16

An area in the mantle from which the heat rises as a hot thermal plume from deep in the Earth

Question 17

How are hot spot volcanoes formed?

Answer 17

Lithosphere is thinner, high heat and low pressure enables the melting of the rock.
Magma rises through the melted lithosphere and erupts as an active volcano on the surface.
Convection currents move tectonic plates over stationary hot spots, the volcanoes are rafted away, and new volcanoes form in there place over millions of years.
These volcanoes cool and subside, producing older islands, atolls and seamounts.
A chain of islands forms over time.

Question 18

Example of hot spot volcanoes

Answer 18

Hawaiian Islands

Question 19

Describe the structure of the crust

Answer 19

Solid
Composed of O2, Si, Al, Fe, Ca, Na, K, Mg
100km thick
200-400 C

Question 20

Describe the structure of the mantle

Answer 20

Solid in the asthenosphere
Liquid magma in the rest
Composed of Si, Mg and Fe
2900km thick
84% of Earth's volume
1000-3700 C

Question 21

Describe the structure of outer core

Answer 21

Liquid
Composed of Fe and Ni
2200km thick
4500-5500 C

Question 22

Describe the structure of the core

Answer 22

Solid
Composed of Fe
1278km thick
4400-6000 C