11. Tectonics Review

Earthquakes and Volcanoes

Source : http://www.thegeographeronline.net/plate-tectonics.html

​Watch the above YouTube about our earth and try to give me 5 pieces of information about the structure of our planet and the processes that go on inside it.

The Earth's Structure

INTERACTIVE EARTH LAYERS LINK- Go to it....

INteractive Layers site 2

Interactive site #3

Interactive Site #4

INteractive Site 5

CONVECTION CELLS CLICK IMAGE AND FOLLOW LINK- TECTONICS

Tectonic plates and their distribution

GO HERE AND USE THIS SLIDE SHOW TO COMPLETE MAP

Types of Plate boundary

There are different kinds of plate movement creating 3 general kinds of plate tectonic boundaries:

divergent, convergent, and transform plate boundaries.

This image shows the three main types of plate boundaries: divergent, convergent, and transform.

A divergent boundary occurs when two tectonic plates move away from each other. Along these boundaries, lava spews from long fissures and geysers spurt superheated water. Frequent earthquakes strike along the rift. Beneath the rift, magma—molten rock—rises from the mantle. It oozes up into the gap and hardens into solid rock, forming new crust on the torn edges of the plates. Magma from the mantle solidifies into basalt, a dark, dense rock that underlies the ocean floor. Thus at divergent boundaries, oceanic crust, made of basalt, is created.

When two plates come together, it is known as a convergent boundary. The impact of the two colliding plates buckles the edge of one or both plates up into a rugged mountain range, and sometimes bends the other down into a deep seafloor trench. A chain of volcanoes often forms parallel to the boundary, to the mountain range, and to the trench. Powerful earthquakes shake a wide area on both sides of the boundary.

If one of the colliding plates is topped with oceanic crust, it is forced down into the mantle where it begins to melt. Magma rises into and through the other plate, solidifying into new crust. Magma formed from melting plates solidifies into granite, a light colored, low-density rock that makes up the continents. Thus at convergent boundaries, continental crust, made of granite, is created, and oceanic crust is destroyed.

Two plates sliding past each other forms a transform plate boundary. Natural or human-made structures that cross a transform boundary are offset—split into pieces and carried in opposite directions. Rocks that line the boundary are pulverized as the plates grind along, creating a linear fault valley or undersea canyon. As the plates alternately jam and jump against each other, earthquakes rattle through a wide boundary zone. In contrast to convergent and divergent boundaries, no magma is formed. Thus, crust is cracked and broken at transform margins, but is not created or destroyed.

Did You Know?

The Chile triple junction is the only modern site on Earth where an actively spreading mid-ocean ridge crest is being swallowed by a subduction zone at a continental margin. This is a particularly interesting area to study because we can observe two types of plate boundaries (divergent and convergent) and their processes in very close proximity.

There are three different types of plate movement. These create five different types of boundaries.

Different types of plate boundary (movement)

Draw and explain the 4 types of plate boundary seen above. Diagrams need to be detailed and labelled.

Types of Volcanoes

Volcanoes are categorized in many different ways. The main ones are:

• Activity level
• Shape and composition

Activity Level

This looks at how long ago the volcano exhibited any sort of life.

• Active: Have erupted in the last 80 years - there are about 540 of them in the world.
• Dormant: Resting but which may erupt again in the future.
• Extinct: Dead and will not erupt again

Note: How active a volcano is largely depends on where it is found in the world. Certain regions are more volcanically active than others, for example the Ring of Fire which runs all the way round the edges of the pacific ocean.

Create an information leaflet with labelled diagrams explaining the difference between:

​(all diagrams should be hand drawn)

Features and Dangers of a volcano

Reduction of Risks and Advantages of living in a volcanic area

Using pages 99 - 101 of your textbook 'Complete Geography for Cambridge IGCSE' identify and explain (create a MindMap):

Volcano Case Study

Earthquakes

INTERACTIVE QUIZ

Earthquake: a series of vibrations induced in the earth's crust by the abruptrupture and rebound of rocks in which elastic strain has been slowly accumulating.

Explain what is an earthquake, how does it occur? (Draw a labelled diagram)

See page 88 in your Textbook (Geography 2nd Edition, Hodder)

Monitoring Eathquakes

​Examine the two photographs below . What information do seismographs tell us?

Tsunami

A tsunami is also known as a seismic sea wave, is a series of water waves caused by the displacement of a large volume of a body of water, generally an ocean or a large lake. Earthquakes, volcanic eruptions and other underwater explosions (including detonations of underwater nuclear devices), landslides, glacier calvings, meteorite impacts and other disturbances above or below water all have the potential to generate a tsunami.

Earthquake hazards and responses

Class project:

This is an assessed piece of work (work to be completed individually or in pairs). Your task is to create a presentation covering the areas below. You will need to research this on the internet.

It will be scored out of 20 marks [5 for presentation, 5 for completeness, 2x5 for content in areas 1 and 2] (see below)

1. Outline what hazards earthquakes can cause (building collapse, liquifaction, tsunamis etc - list with brief description)
2. Seperate the hazards into primary and secondary
3. What methods are available to reduce their impact (anti seismic structures, hazard mapping etc)

Possible source:

METHODS OF REDUCING EARTHQUAKE HAZARDS

Play the Earthquake game

Earthquake Case Study

Create a detailed case study of the Nepal 2015 earthquake

Test Yourself - Revision