1.1 revision class 2013

Year 11 GeoSeptember Exam 2013

When Tuesday 17th September 1pm

What do I need ? PenS (more than one) Coloured pencils Ruler Calculator

1.1 Extreme Natural Events

How have natural processes led to your natural event

Explain the effects of the natural event on the cultural environment

Explain the effects of the natural event on the natural environment

Chosen extreme natural event Our chosen extreme natural event is

……… VOLCANIC ERUPTIONS

You need to know about volcanic eruptions and you also MUST bring name at least one case study example in your answer

E.g. Mt Tarawera in 1886 or Mt Pinatubo in 1991 or Nevada del Ruiz in 1985

How have natural processes led to your natural event? This question is asking about the

sequence of events that cause a volcanic eruption.

What processes do you remember that cause volcanic eruptions?

The earth is made up of 12 major plates that float on the earth’s semi liquid mantle layer. NZ sits between the Pacific plates and Australian plates

Plates can be either CONTINENTAL (mostly land) - these are thicker but less dense or OCEANIC (mostly sea) – these are thinner but more dense/heavier

The earth’s plates move independently of one another at rates of 1-15 cm per year as convection currents occur in the mantle. The mantle is heated by the core causing it to rise and fall

When an oceanic and continental plate are pushed together by convection currents, subduction occurs. This is when the denser, oceanic plate is forced below the lighter, continental platee.g. this happens off the east coast of the North Island of NZ

where the Pacific plate subducts below the Australian plate at a rate of 8cm a year

As the oceanic plate is forced beneath the continental plate, intense friction and heat is caused as the plates rub together. This heat then melts the plate as it sinks into the mantle, creating magma which collects in a magma chamber

e.g. Mt Ruapehu’s magma chamber sits 100km below the earth’s surface

Pressure builds up in the magma chamber as gases are produced like carbon dioxide and sulfur dioxide

This pressure builds up then forces the magma to make its way up to the earth’s surface through weak spots or cracks known as fissures in the earth’s crust

Before an eruption can begin, sometimes a plug (old, solidified lava in the vent) must be blasted out of the way first.

When magma reaches the earth’s surface, gases like carbon monoxide are released first, this means magma has become lava. Lava and rocks are erupted into the air and will fall around the crater to eventually form the volcano’s cone. The more gas and silica contained in the lava, the more viscous (less runny) the lava will bee.g. Mt Ruapehu was formed from rhyolite lava meaning the

lava was very viscous and this has given it a very uneven, jagged shaped cone with a height of 2797m

Hints for EXCELLENCE Include case study detail THROUGHOUT your

answer instead of in a clump in the end Draw a well labelled diagram that sums up the

overall process and refer to it in your written answer

Include the definition of the CONCEPT given to you in your answer. E.g. A process is a series of related events. The natural process of subduction works as a series of steps to create volcanic eruptions

Explain the effects of the natural event on the cultural environment

We can divide the effects of a volcanic eruption on a cultural environment into TWO different categories.

SOCIAL this means people’s daily lives and feelings are

impacted ECONOMIC this means businesses

and money are impacted

Remember effects can be both POSITIVE and NEGATIVE

You MUST refer to at least ONE case study example in your answer.

Ideally, for each effect you will have a piece of case study detail to back up what you are saying

Negative Social Effects could include…. Loss of life from ash inhalation, pyroclastic flows

or lahars occurring during the volcanic eruption Houses destroyed and people injured, this

makes people feel angry and upset as they will become homeless

Ashfall from volcanic eruptions can damage and destroy crops meaning people will go hungry

Motorways can become blocked and communications cut off so people feel isolated as they are unable to travel

Positive Social effects could include…… Communities come together to help in

the recovery process after a volcanic eruption

Negative Economic effects could include…… Livestock may become sick or die after

eating ash covered grass so farming businesses will lose money

Skifields maybe forced to close during an eruption costing them a loss in profit

The cost to repair the infrastructure damaged can be extensive, increasing tax for the rest of the population

Positive Economic Effects could include…. New tourist destinations, like crater lake

tours and geothermal valleys can be created which means businesses can develop bringing money to the region

Increased geothermal activity can lead to increased profits for local electricity companies

Hints for EXCELLENCE Try to give a piece of case study information

for each effect e.g. A negative economic effect is that natural landscapes like the Pink and White terraces that brought tourists to the area can be destroyed by volcanic activity. This occurred during the June 1886 eruption of Mt Tarawera when the Pink and White terraces were lost during the eruption under 22 metres of ash. This meant a loss of tourism and money to the Rotorua area.

Hints for EXCELLENCE If you are given a CONCEPT

definition in the question USE THIS IN YOUR ANSWER

Organise your answer into categories – 1 paragraph on social effects (positive and negative) and 1 paragraph on economic effects (positive and negative)

We can divide the effects of a volcanic eruption on the natural environment into 4 categories

Relief (shape of the land) Soil Vegetation Drainage patterns (lakes and rivers)

You should learn a map of your case study area that you can locate these effects on

Explain the effects of the natural event on the natural environment

e.g. This is a case study area map of MT TARAWERA – this would be useful for both NATURAL and CULTURAL effects on the environment

Relief effects could include… The shape of the land is changed as

features like volcanic cones are destroyed by explosive volcanic eruptions, new cones are built up by build up of new lava or chasms/splits in the landscape are created during the eruption

Soil effects could include…. Excess ash deposits can make the soil more

acidic and this results in it being infertile

BE CAREFUL HERE that you DO NOT talk about crops as this is an effect on PEOPLE not the natural environment

Soil can be eroded from the landscape as lahars move quickly down the volcano

Vegetation effects could include… Ash covers trees and vegetation which

limits the regrowth of the young trees Forests surrounding a volcano can be

burnt or flattened by pyroclastic flows Lahars can strip vegetation off the sides

of volcanoes as the move quickly down the landscape

Drainage effects could include… Lakes can be enlarged during the

eruption or created if it is an active vent Rivers can become discoloured by ash

and pathways can change as they become clogged by volcanic sediment

Hints for EXCELLENCE Again, try to give a piece of case study

information for each effect e.g. An effect on the relief of the natural landscapes can be seen when an eruption creates and destroys new landform features from the force of the explosion. This occurred during the 1991 Mt Pinatubo eruption when the top of the volcano was replaced by a new caldera 2.5km wide and the height of the volcano was decreased by 260m.

Hints for EXCELLENCE If you are given a CONCEPT

definition in the question USE THIS IN YOUR ANSWER

Organise your answer into categories – 1 paragraph on relief effects, 1 paragraph on soil effects, 1 paragraph on drainage patterns and 1 on vegetation

Whats going to be in it ? 1.2 Explain how natural and cultural factors

have led to population distribution The Migration Model with Specifics from

India or New Zealand The Effects that migration has had on

india The sustainability of the Indian

Population