The Earth's Surface 

\

Structure of the earth

• [[The crust[[
    * The crust is the outside layer
    * Made of solid rock
    * Oceans and continents lie on top of the crust
• ]]The mantle]]
    * The mantle lies under the crust
    * Made of magma
    * The magma is moved around by convection currents
• {{The core{{
    * The centre of the earth
    * Made of iron and nickle
    * Hottest part => 6000 degrees
    * Can be divided into the inner core and the outer core

Plates

• The earths crust is broken into plates
• Plates with land on top = $continental plates$
• Plates with ocean on top = $oceanic plates$
• The line where two plates meet = $plate boundary$

Convection currents

• The plates lie on top of the mantle
• Magma in the mantle is moved around by convection currents = causes plates to move
• Plates can
    * $Collide$
    * $Separate$
    * $Slide$

Plate tectonics

The study of plates and their movement is called $plate tectonics$

$Pangaea$: All the continents joined together

• Pangaea then broke up by $continental drift$
• Proof: Mid-Atlantic Ridge

What happens at each of the plate boundaries?

Plates collide

• $Destructive$ boundaries
• Crust is $destroyed$
• $Subduction$: Heavier plate (oceanic) is pushed under the lighter plate (continental)
• Colliding plates cause:
    * $Fold mountains$
    * $Earthquakes$
    * $Volcanoes$
• Example:
    * The Andes

Plates separate

• $Constructive$ boundary
• New crust is $formed$
• Plates move apart and magma moves in to fill the gap, which cools and hardens to form new crust
    * When this happens under the sea it’s called $sea-floor spreading$
• Separating plates cause:
    * $Volcanic mountains$
    * $Volcanic islands$
• Example:
    * The Iceland

Plates slide

• $Passive$ boundary
• Crust is $neither created or destroyed$
• Plates lock and release a huge amount when the $pressure$ is released
• Sliding plates cause:
    * $Earthquakes$
    * $Fault line$
• Example:
    * San Andreas Fault

Volcanic Activity

$Ring of fire:$ the edge of the pacific where most volcanic activity happens

Volcanic activity causes:

• $Mid-oceanic ridges$
• $Volcanic island$
• $Volcanic mountains$

Mid-oceanic ridges

Hot molten magma rises up from the mantle, through the cracks in the crust. This mama cools, hardens and builds up, forming a ridge of rock

Example:

• The $Mid-Atlantic Ridge$
• Where the South American Plate from the African/Eurasian Plate

Volcanic island

When underwater mountains rise above the surface of the ocean

Example:

• $Iceland$

Volcanic mountain

Formed when magma rises up from a magma chamber through a vent to reach the Earth’s surface. When magma reaches the surface of the earth it’s called lava.

When lava, hot ash and rocks are throw into the air from the vent we call it an eruption. After many eruptions, layers of material build up around the vent to form a a cone shaped volcanic mountain or volcano.

Parts of a volcano

Example:

• Mount St Helens, USA

Types of volcano:

• %%Active%%
    * Erupt regularly
    * Example: Mount St Helens, USA
• $Dormant$
    * Might not erupt for a long time but might erupt again
    * Mount Vesuvius, Italy
• ==Extinct==
    * Extinct volcanoes will not erupt again
    * Croghan Hill, Co. Offaly

Socio-economic effects of volcanoes

$Socio-economic$: to do with both social factors and economic factors and how they relate to eachother

%%Positive effects:%%

• The soils near volcanoes are $rich in minerals$ and are very suitable for $agriculture$. This means that people can farm and sell more produce
    * Campania in Italy has very fertile soils as it lies next to mount Vesuvius
• Volcanic regions are very good $tourist$ sites
• Water heated underground by volcanic activity can be used to make $geothermal energy$ to heat peoples home’s
    * Geothermal energy is very popular in $Iceland$

==Negative effects:==

• $Sulfur dioxide$ is produced by volcanoes and can poison people nearby and can cause $acid rain$
• Lava flow burns everything in it’s path and can result in huge $loss of life$
• When volcanic matter mixes with rain or snow it can result in a $lahar$

Volcanic activity in Ireland

• Evidence for extinct Irish volcanoes 450 million years ago:
    * The Giant’s Causeway: Igneous rock
    * Lambay Island, Co. Dublin

Case Study: Volcanic activity in Iceland

The physical landscape, social and economic activities are very influenced by volcanic activity as Iceland is located on the $Mid-Atlantic Ridge$

Geothermal energy

• $Geothermal energy$ is one of the $cheapes$t and most $sustainable$ forms of energy
• $Steam$ from geothermal energy is used to create $electricit$y which provides factories, offices and houses with power
• $Water$ heated by geothermal energy can be used to $heat homes$

Agriculture

• Iceland is self-sufficient in the production of meat
• $Self sufficient:$ does’t need to import products
• Crops are grown in $greenhouses$ that are heated by $geothermal energy$
• Water is used $sustainably$
• Ireland doesn’t receive much daylight in winter, however $cheap geothermal energy$ can be used to create $artificial light$ in greenhouses

Tourism

• Natural tourist attractions:
    * $Black sand beaches$
    * $Geysers$
    * $Geothermal spas$
• %%Positive impacts%%
    * Tourism provides $jobs$
• ==Negative impacts==
    * $Soil erosion$ and litter from tourists

Case Study: Natural disaster: Mount St Helens

%%Short-term responses%%

• As the volcano was $monitored$ and predicted to erupt, people were $evacuated$
• $Ash$ took 10 weeks and millions of dollars to remove
    * Provided 200,000 $jobs$
• $Electricity$ was restored

^^Long term responses^^

• Millions of $trees$ were $replanted$
• Farmers were given $compensation$ for their losses
• Government gave money to $rebuild damaged buildings$ and $transport$

Earthquakes

• Earthquakes are sudden $tremours$ in the Earth’s crust
• Caused by $released pressure$ of $colliding$ or $sliding plates$
• 
• Smaller tremors after an earthquake are called $aftershocks$

Measuring earthquakes

• $Seismologist$: A person who studies earthquake activity
• $Seismograph$: Used to measure tremors in the earth’s crust
• $Richter$ scale: A scale ranging between 1-10, each unit is 10 times stronger than the one before it
• $Moment magnitude scale$: Mw

Damage caused by earthquakes

• $Loss of life$
• Building can $collapse$ or get $damaged$
• Damage to electricity lines or gas pipes can cause $fires$
• Damage to $sewers$ and water supplies can spread $disease$
• When $bridges$, $roads$ and $railways$ are broken it can effect $transport$ in and out of the area
• $Landslides$ and $avalanches$ can be triggered
• $Tsunami$: huge wave caused by an earthquake underwater

How to reduce the damage caused by earthquakes

• Earthquake resistant buildings
    * $Shock absorbers$
    * $Reinforcing walls with steel$
    * $Tuned mass dampers$
• Earthquake and tsunami drills
• Early-warning systems

Case study: Earthquake in Japan

On March 11 2011 an 8.9 earthquake hit Japan which also caused a tsunami

%%Short term responses%%

• After the earthquake a $tsunami warning$ was issued and coastal areas were $evacuated$
• People living near the nuclear power plant were checked for signs of $radiation$
• $Temporary camps$ were set up for the $homeless$
• $Debris$ was cleaned up
• Other countries offered $emergency aid$

^^Long term responses^^

• Electricity and water supplies were restored
• Roads and airports were repaired
• Houses and other building were repaired or rebuilt

Fold mountains

When two plates collide with each other a fold mountain forms

• Heavier plate sinks under the lighter plate
• Lighter plate $buckles$ because it has nowhere to go making $fold mountains$

or

• If two lighter plates collide they both $buckle upwards$

Example:

• The Andes

Periods of folding

$Alpine$

• Highest mountains
• 30-35 million years ago
• Examples:
    * The Alps
    * The Andes
    * Himalayas

@@Armorican@@

• When Eurasian and African plate collided
• 250 million years ago
• Examples:
    * MacGillycuddy’s Reeks
    * Black forest, Germany

==Caledonian==

• When Eurasian Plate and American plate collided
• 400 million years ago
• Examples:
    * Dublin and Wicklow mountains

Mountains and people

Tourism

• People are attracted to the $beautiful scenery$
• $Leisure activities$
    * Hill walking
    * Skiing
    * Rock climbing
• Provides $employment$
• $Pollution$ and littering

Farming

• $Cattle$ and $sheep$
• Difficult to use $machinery$

Forestry

• Forestry is usually the only suitable economic activity
• Felling of trees can cause soil $erosion$ and $landslides$

\