Restless Earth - created from Mind Map

Seite 1

The Earth

Lithosphere

Mantle

Core

Continental Crust

Oceanic Crust

Solid

Makes up most of the land area of the Earth

Granite

Up to 900 degrees

Between 25-80 km thick

Solid

6-8 km thick

Basalt

Up to 900 degrees

Asthenosphere

Mantle

Partially Molten

Periodotites

1000-1600 degrees

Solid

Silica-based minerals

1600-4000 degrees

Outer core

Inner core

Liquid:Very dense

Iron/Nickel

4000-5000 degrees

Solid: Very dense

Iron/Nickel

4000-5000 degrees

Tectonic Activity

High temperatures in the core are caused by radioactive decay

These create rising limbs of material, called convection currents.

These cool and spread out as they rise before sinking again

Some of this material moves in sheets creating movement in the crust

This is pulled apart, creating new crust

In some places it rises, creating hotspots.

Plate Boundaries

Destructive Margins

Constructive Margins

Conservative Margins

Where Oceanic plates collide with Continental plates

The denser basaltic oceanic plate sinks beneath the constructive

EG: Nazca and South American Plates

This is subduction

This creates a deep ocean trench

As the oceanic plate is subducted into the mantle, pressure and temperature increase.

Lightweight materials rise to the surface, forming volcanoes

The collision also lifts and buckles the continental plate

Long chains of volcanoes (volcanic arcs) are located about subducted plates

Usually above where plates have reached a depth of 100 km

This creates fold mountains

Formed by rising magma splitting the continental crust, forming new oceans,

EG: Mid-Atlantic Ridge

Where plates slide past each other or move in the same direction at different speeds.

No crust is formed or destroyed

Causes strain

No volcanoes formed

Earthquakes are frequent and often large

EG: San Andreas Fault

Hazards and Causes

Impacts depend on

Where they occur

Types of Volcano

Earthquakes can't be predicted so are genererally more dangerous

Impacts of Earthquakes

Size of event

Vulnerability of population

How prepared the country was

Volcanic eruptions generate earthquakes

Earthquakes occur on conservative margins

Not all volcanoes or earthquakes occur on plate boundaries

Some do so at hotspots

Composite

Shield

Steep sided, small area, alternate layers of ash and lava

Viscous/sticky

Flows Slowly

Often freezes in central vent

Granatic or andesitic magma

Infrequent unpredictable explosions

Pressure builds up over time

Gentle slopes

Large area

Almost all lava

Fluid flows quickly from many fissures

Basaltic magma

Very frequent gentle eruptions

Both volcanoes and earthquakes can cause tsunamis

Tsunamis

Are a series of destructive ocean waves

Travel at up to 900 km /h

Can be up to 20-30 m high

EG: Indian Ocean tsunami of 2004 26th December killed 250,000 people in 14 countries.

Factors controlling the severity

The magnitude of the Earthquake on the richter scale

The depth. (Shallow are more destructive)

The distance from the epicentre

The time of day

The level of preparedness

Quality of emergency services

Predicting and Preparing for Hazards

Predicting

Preparing

Bulging of volcanoes can be measured

Tsunami warning sirens help evacuate people

Evacuation routes can be planned

Mitigation

Hazard resistant buildings

Disaster kits

Landuse Planning

Make foundations deep but allow movement

Build in shock absorbers

Cross bracing prevents floors collapsing

Reduce roof weight

Use lighter bricks

Strengthen wall corners with wire mesh and cement

Restless Earth