Geography- Earth, volcanoes, plate tectonics

Earth layers

inner core

outer core

mantle

crust

characteristics of the inner core

is in the centre and is the hottest part of the Earth. It is solid and made up of iron and nickel with high temperatures

characteristics of the outer core

layer surrounding the inner core. It is a liquid layer, also made up of iron and nickel. It is still extremely hot, with temperatures similar to the inner core.

characteristics of the mantle( asthenosphere)

the widest section of the Earth.The mantle is made up of semi-molten rock called magma. In the upper parts of the mantle the rock is hard, but lower down the rock is soft and beginning to melt.

characteristics of the crust( lithosphere)

thinnest layer of the earth. it is the solid rock layer upon which we live.

two different types of crust

continental crust- which carries land,

oceanic crust- which carries water.

plate tectonics

the movement of the plates, and the activity inside the Earth

theory of plate tectonics

Earth's solid outer crust, the lithosphere, is separated into plates that move over the upper mantle

process of theory of plate tectonics

The heat rising and falling inside the mantle creates convection currents generated by radioactive decay in the core. The convection currents move the plates.

PLATE Distribution

The Earth's crust is broken up into pieces called plates.

Where are earthquakes most likely to occur?

near or on plate boundaries

PLATE BOUNDARY

the place where two plates meet

3 types of plate boundaries

constructive plate boundary

destructive plate boundary

conservative plate boundary

CONSTRUCTIVE BOUNDARY (Divergent Boundary )

plates are moving apart. As the plates move apart magma rises from the mantle. The magma erupts to the surface of the Earth. This is accompanied by earthquakes. When the magma reaches the surface, it cools and solidifies to form a new crust of igneous rock.

- they tend to be found under the sea

- no fold mountains

DESTRUCTIVE BOUNDARY (Convergent boundary)

plates are moving towards each other. This usually involves a continental plate and an oceanic plate.The oceanic plate is denser than the continental plate so, as they move together, the oceanic plate is forced underneath the continental plate.Also known as subduction zone. As the oceanic plate is forced below the continental plate it melts to form magma and earthquakes are triggered. The magma collects to form a magma chamber. This magma then rises up through cracks in the continental crust.As pressure builds up, a volcanic eruption may occur.

- fold mountains

folding

As the plates push together, the continental crust is squashed together and forced upwards

fold mountains

created through the process of folding. can also be formed where two continental plates push towards each other. This is how mountain ranges such as the Himalayas is formed.Fold mountains occur near destructive plate boundaries

The formation of fold mountains

•Where an area of sea separates two plates, sediments settle on the sea floor. These sediments gradually become compressed into sedimentary rock.

• When the two plates move towards each other again, the layers of sedimentary rock on the sea floor become crumpled and folded.

•Eventually the sedimentary rock appears above sea level as a range of fold mountains.

SUBDUCTION ZONES

Seduction happens when tectonic plates shift, and one plate is pushed under another.This movement of the ocean floor produces a mineral transmutation. which leads to the melting and solidification of magma and the formation of volcanoes.

- happen at destructive plate boundary

CONSERVATIVE BOUNDARY (transform boundary)

plates move past each other ,side by side moving at different speeds. As the plates move, friction occurs and plates become stuck. Pressure builds up because the plates are still trying to move. When the pressure is released, it sends out huge amounts of energy, causing an earthquake. The earthquakes at a conservative plate boundary can be very destructive as they occur close to the Earth's surface.

• cause earthquakes

- they have no volcanoes

- no fold mountains

The Ring of Fire

path along the Pacific Ocean characterized by active volcanoes and frequent earthquakes.

earthquake

the shaking and vibration of the Earth's crust due to movement of the Earth's plates

how do earthquakes occur

occur when tension is released from inside the crust. Plates do not always move smoothly alongside each other and sometimes get stuck. When this happens pressure builds up

focus

The point inside the crust where the pressure is released

epicentre

point on the Earth's surface above the focus. it is where the most severe damage caused by an earthquake happens

How is earthquake energy released?

in seismic waves

How seismic waves travel

These waves spread out from the focus. The waves are felt most strongly at the epicentre, becoming less strong as they travel further away.

Deep focus earthquakes

associated with Subduction zones

- destructive plate boundary

Shallow focus earthquakes

located along conservative plate boundaries where two plates move past each other

seismometer

measures the power of an earthquake. by detecting the vibrations caused by an earthquake and plotting them in a seismograph.

Ritcher scale

measures magnitude or strength of an earthquake

human activities that cause earthquakes

Nuclear testing

Building large dams

Drilling for oil/ natural gas

Coal mining

short term Effects of an earthquake- Social

people die

homes destroyed

communication and transport links disrupted

water pipes and gas pipes may burst

short term Effects of an earthquake- economic

shops and businesses destroyed

damaged communication and transport links

short term Effects of an earthquake- environmental

built landscape destroyed

fires can spread due to gas pipes bursting

landslides and flooding due to tsunamis may occur

long term Effects of an earthquake- Social

diseases may spread

people may have to be re-located

long term Effects of an earthquake- economic

cost of rebuilding is high

income lost

only certain areas heavily affected by the earthquakes may be fixed taking away the money that could have been used for other places

long term Effects of an earthquake- environmental

important human landmarks may be lost

water contamination

Factors affecting the impact of an earthquake

-Distance from the epicentre - the effects of an earthquake are more severe at its centre.

-The higher on the Richter scale- the more severe the earthquake is.

-Level of development - MEDCs are more likely to have the resources and technology for monitoring, prediction and response.

-Population density (rural or urban area)- The more densely populated an area, the more likely there are to be deaths and casualties.

-Communication - accessibility for rescue teams.

The effects of an earthquake in LEDCs

-Communication systems may be underdeveloped- so the population may not be well educated about what to do in the event of a volcanic eruption or an earthquake.

-Construction standards tend to be poor in LEDCs.- Homes and other buildings may suffer serious damage when a disaster occurs.

-Evacuation and other emergency plans can be difficult to put into action due to limited funds and resources.

-There may not be enough money to rebuild homes quickly and safely.

-Many people could be forced to live in emergency housing or refugee camps.

Prediction

involves using seismometers to monitor Earth tremors. Experts know where earthquakes are likely to happen.

However, it is very difficult to predict when they will happen.

Protection

Many areas prone to earthquake hazards now use building codes. Any new building or adjustment to existing buildings must be carried out to strict guidelines to help protect people from future earthquake hazards.

examples of building improvements from earthquakes

-rubber shock absorbers in the foundations to absorb the Earth tremors

-steel frames that can sway during Earth movements

-open areas outside of the buildings where people can assemble during an evacuation

-Lightweight roofs designed to reduce damage and injury

Volcano

an opening in the Earth's crust that allows magma, hot ash and gases to escape

How volcanoes form

-Pressure builds up inside the Earth.

-When this pressure is released, as a result of plate movement, magma explodes to the surface causing a volcanic eruption.

-Magma rises through cracks or weaknesses in the Earth's crust.

-The lava from the eruption cools to form new crust.

-Over time, after several eruptions, the rock builds up and a volcano forms

volcanoes occur at

They occur at destructive and constructive plate boundaries.

- but not at conservative boundaries.

magma chamber

collection of magma inside the Earth, below the volcano

main vent

main outlet for the magma to escape.

Secondary vents

smaller outlets through which magma escapes

crater

created after an eruption blows the top off the volcano.

eruption occurs when

pressure in the magma chamber forces magma up the main vent, towards the crater at the top of the volcano. Some magma will also be forced out of the secondary vent at the side of the volcano

Volcanoes can be described in terms of activity

-Still active and erupt frequently.

-Dormant -temporarily inactive but not fully extinct

- Extinct-never likely to erupt again

Different types of volcano

- Shield volcanoes

- Strato volcanoes / composite volcano

- Cinder Cones

Shield volcanoes

-Shield volcanoes are usually found at constructive boundaries.

-They are low, gently sloping sides.

-They are formed by eruptions of thin, runny lava.

-Eruptions tend to be frequent but relatively gentle.

- largest of all the volcanoes on the earth, which are not steep.

-mostly made up of basalt.

-become explosive if in some way water gets into the vent, otherwise, they are characterized by low-explosivity.

- The lava that is moving upwards does so in a fountain-form and emanates the cone at the vent's top and then develops into a cinder cone.

•Eg: Hawaiian shield volcanoes

pyroclastic flow

-mixture of hot steam, ash, rock and dust.

can roll down the sides of volcanoes at high speed

Strato volcanoes / composite volcano

- are made up of alternating layers of lava and ash

- found at destructive boundaries.

- eruptions from these volcanoes may be a pyroclastic flow rather than a lava flow.

ex: Mayon Volcano in the Philippines, Mount Fuji in Japan, and Mount Rainier in Washington

Cinder Cones

-smallest and most common type of volcano.

-cone shape, but is much smaller than a composite volcano.

- found ag destructive boundary

- have steep sides.

- composed of small fragments of rock,

ex: Mauna Kea, a volcano on the American island of Hawaii, and Mount Etna, a volcano on the Italian island of Sicily,

What are the advantages of Volcanoes?

- attracts tourists bringing income to the area

- lava and ash give valuable nutrients and create fertile soils

- give geothermal energy

What are the disadvantages of Volcanoes?

- lives lost

- pollution

- kills crops

- destroys infrastructure

warning signs of volcanoes

- rise in temperature

- small earthquakes

- release of gas

Monitoring Techniques for volcanoes

- seismometers- to monitor earthquakes

- thermal imaging- to detect heat around volcano