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Plate Tectonics
Continental crust is also known as sial
and is less dense than sima.

Oceanic crust is known as sima and is
denser than sial.

Oceanic crust is continuous
Continental crust is discontinuous through oceans
Both parts are in a series of interlocked pieces called plates
The point between…

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New parts of a plate rise because they are warm and the plate is thin. As hot magma rises to the
surface at spreading ridges and forms new crust, the new crust pushes the rest of a plate out of its
way. This is called ridge push.
Old parts of…

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It has been proposed that the Earth's magnetic field reverses at intervals ranging from 10000s of
years to millions of years with an average interval of 250000 years. The last event
(Brunhes-Matuyama Reversal) is thought to have occurred 780000 years ago. There is no clear
theory as to how the…

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Viscosity in turn controls the amount of gas that can be trapped in the magma. The greater the
viscosity, the more gas in the magma.

There are three main types of magma:

Basaltic Magma: constructive boundaries - low viscosity, slow cooling, low gas content -
shield volcanoes - gentle eruptions…

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Dyke: magma intrusion into a vertical fault which solidifies. Not usually visible as are small
scale intrusive features. Sometimes a swarm of dykes will form.
Sill: e.g. Great Whin Sill - cooled and solidified magma between two strata (layers of rock)
along the bedding plain. These are not usually visible…

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antisyncinoriums and synclinoriums i.e. a mountain range.

Old and New Fold Mountains

Old Fold Mountains: more weathered and eroded (denudation) and are at lower altitudes
and smoother
o Appolation Mountains
o Scottish Highlands
o Scandinavian Mountains Formed in hercynian orogeny
o Great Dividing Range - Australia
o Urals - Russia…

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Earthquake magnitude is measured using a seismometer or seismograph on a scale of 1-8.

The Mercalli Scale

This measure the intensity i.e. the damage caused rather than the energy
This is a scale of 1-12.

Case Study: The Kashmir Quake 2005

Date: 8th October 2005
Magnitude: 7.6
Depth: 10km

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Case Study: Indonesian Quake 2004

Date: 26th December 2004
Magnitude: 9
Eurasian and Australian Plates
250000 deaths
Strongest earthquake for 40 years
Walls of water tens of metres high hit coastal areas 1000s of miles apart as far away as
Populations were dependant on primary livelihoods meaning they lost…

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Stilts used to prevent damage
Forest planting between the coastline and buildings as trees rapidly slow waves down and
cause them to lose a lot of energy

Continental-Oceanic Convergence

Where oceanic and continental plates meet, the heavier oceanic matter sinks below the
lighter continental plate in the subduction zone.

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Case Study: Mount St. Helens 1980

Major volcanic eruption in Washington state, USA
VEI 5 event
35000 people evacuated
57 people killed
Had been being monitored for 3 months - eruption was predicted
Affected world for 2 years as affected crop production
80000 feet eruption column, depositing ash in 11…


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