volcanoes and earthquakes

What is hazard risk?

The chance or probability of being affected by a natural event.

Why may people live in hazardous areas?

They may weigh up the advantages and disadvantages - often the events happen rarely and they consider it an acceptable risk.

People may not know there is a risk (a volcanoes in Chile hadn't errupted in 9400 years.)

They may not have the education to know.

They may not have a choice due to the rapidly increasing population and limited areas with accomodations.

Areas that previously had little risk are increased through deforestation and/or urbanisation.

How is climate change a factor affecting risk?

Climate change - in a warmer world, the atmoshpehere will have more energy, leading to more intense storms and hurricanes. Climate change may cause part of the world to become wetter with an increased risk of flooding.

How is poverty a factor affecting risk?

Poverty - people may be forced to live in areas of risk. In places such as Lima in Peru and caracas in venezuela, a shortage of housing has led to people building houses on unstable slopes prone to floods and landslides.

How is farming a factor affecting risk?

Farming - when a river floods, it deposits fertile silt on its floodplain, which is excellent for farming, but people who choose to live there are putting themselves at risk. In low lying countries, like Bangladesh, many people live in flooplains.

How is urbanisation a factor affecting risk?

Over 50% of the worlds population now live in cities. Densely populated urban areas are at a great risk from natural events such as earthquakes and tropical cyclones.

How does a natural event become a natural hazards?

There are many ‘natural events in the world such as earthquakes, floods, and landslides. They only become a ‘natural hazard’ when the natural event impacts on people and / or property.

What are the 4 main types hazards can be classified into?

Tectonic - involving the movement of tectonic plates.

Atmospheric - causes of theevent are in the atmosphere

Geomorphological - occuring on the earths surface

Biological - anything involving living organisms.

What are examples of tectonic hazards?

Earthquakes

Tsunamis

Volcanoes

What are examples of atmospheric hazards?

Tornados

Cyclone / hurricanes

Rain and snow

Drought (temp is in the atmosphere.)

What are examples of geomorphological hazards?

Avalanches

Landslides

Floods

Mudflows

What are examples of biological hazards?

Wildfires

Which 4 distinct layers is the earth made up of?

The crust, mantle, outer and inner cores.

Describe the Earth's crust

The outer layer of the earth.

It splits into ‘plates’ of various sizes. These plates can be made up of either continental crust or oceanic crust. This is the thinnest layer of the earth, only 5-10kms thick at the oceanic crust but can be 20-200kms thick at the continental crust.

The oceanic crust may be thinner, but its more dense, so it can sink below the continental crust and become destroyed or renewed.

Describe the Earth's mantle.

Its solid but still able to flow very slowly. It makes up most of the earth and is very hot - around 5000 degrees c.

The upper portion of the mantle is a weak layer that can deform like plastic.

These high temperatures create ‘convection currents’ where the heat rises within the magma, cools down slightly as it reaches the surface (crust) and then sinks towards the core.

This ‘cycle’ creates movement, which moves the plates on the crust.

Describe the Earth's core.

This is the densest part of the earth. The inner core is solid, made up from iron and nickel and is around 6000 degrees c. The outer core is semi molten and slightly less hot.

As there is little evidence for the idea of convection currents, how do scientists explain the movement of plates?

Through the ideas of ridge push and slab pull.

What is ridge push and slab pull?

At plate margins where the crust is moving away from each other, ocean ridges form high above the ocean floor. Beneath the ridges, the mantle melts, the magma rises and cools down to form new material.

As the lithosphere cools, it becomes denser and starts to slide away from the ridge, which causes plates to move away from eachother.

This is called ‘ridge push.’ at destructive margins, the denser oceanic plate sinks back into the mantle under the influence of gravity, which pulls the rest of the plate behind it. This is called ‘slab pull.’

Where are fold mountains located?

They're distributed along plate margins where continental crust is being uplifted.

This includes the continental crust at destructive margins, such as on the West Coast of South America. They also occur at collision margins between 2 continental crusts, such as the Himalayas that span several countries, including China and India.

Where are ocean trenches located?

At subduction zones where oceanic crust descends below continental crust at destructive plate margins.

This includes the areas around the Pacific Ocean known as the ‘pacific ring of fire’ such as off the West Coast of South America.

What are fold mountains?

Mountains that have formed through collision plates.

Young fold mountains include the Himalayas. Rockies, andes and alps.

What are both fold mountains and ocean trenches a result of? What happens if they both form in the same place?

Plates moving towards eachother.

If both landforms occur in the same place, then they're associated with subduction and destructive plate margins/boundaries. If, however, fold mountains occur by themselves, they're in areas where collision is taking place.

How is a subduction zone formed?

At some convergent boundaries, an oceanic plate collides with a continental plate.

Oceanic crust tends to be denser and thinner than continental crust, so the denser oceanic crust gets bent and pulled under, or subducted, beneath the lighter and thicker continental crust.

What happens as the oceanic crust sinks in the subduction zone?

A deep oceanic trench or valley is formed at the edge of the continent.

The crust continues to be forced deeper into the earth, where high heat and pressure cause trapped water and other gases to be released from it.

This, in turn makes the base of the crust melt, forming magma.

What happens after magma is formed at a subduction zone?

It rises up towards the Earth's surface and creates volcanoes on the continental plate.

When the magma finds its way to the surface through a vent in the crust, the volcano errupts, xpelling lava and ash.

(An example of this is the band of active volcanos that encircle the Pacific Ocean, often referred to as the ring of fire.)

Other than by an oceanic crust being subducted under the continental crust, how else is a subduction zone formed?

When two oceanic plates collide - the older plate is forced under the younger one and it leads to the formation of chains of volcanic islands know as arcs.

What else can occur from the collision and subduction of plates?

As its not a smooth process, large, powerful earthquakes can occur. These earthquakes can also cause tsunamis.

What is a tsunami?

a huge ocean wave caused by a sudden shift on the ocean floor, such as an undersea earthquake. If the wave reaches land, it can cause incredible destruction.

What is a continental crust?

The Earth's crust that makes up the continent.

What is oceanic crust?

The Earth's crust found underneath oceans.

What is a subduction zone?

The area where ne plate is being pulled under the edge of another.

What is an (ocean) trench?

a steep sided depression on the sea floor.

What is a volcanic arc?

A chain of volcanoes formed above a subduction zone.

At constructive / divergent plate margins / boundaries are plates moving towards or away from eachother?

They're moving apart.

What is sea floor spreading?

When constructive margins occur under the ocean. As plates made of oceanic crust pull apart, a crack in the ocean floor appears.

What is a rift (valley)?

When two continental plates move apart, rift valley develop. It is a ‘dropped’ zone where the plates are pulling apart. As the crust widens and thins, valleys form in and around the area, as do volcanoes, which may become increasingly active.

Early in its formation, streams and rivers flow into the low valleys and long, narrow lakes can be created. Eventually, the widening crust along the boundary may become thin enough that a piece of the continent breaks off, forming a new tectonic plate.

At this point, water from ocean will rush in, forming a new sea or ocean basin in this zone.

What causes a fault - crack or fracture in the Earth's crust?

At conservative / transform plate margins / boundaries, the tectonic plates aren't moving directly away or towards eachother. Instead, 2 tectonic plates grind past eachother in a horizontal direction.

This kind of boundary results in the fault in the earths crust.

These plates can be moving in opposite directions or the same direction, but at different rates.

What and why do transform boundaries and the resulting faults produce?

Many earthquakes - because edges of tectonic plates are jagged rather than smooth. As the plates grind past eachother, the jagged edges strike eachother, catch and stick, ‘locking’ the plates in place for a time.

Because the plates are locked together without moving, a lot of stress builds up at the fault line. This stress is released in quick bursts when the plates suddenly slip into new positions. The sudden movement is what we feel as the shaking and trembling of an earthquake.

What is a primary effect?

The immediate effects of the volcano, caused by it directly.

What is a secondary effect?

The after-effects that occur as an indirect effect of the erupiton on a longer timescale.

What are impacts?

What happens to life and/or property as a result of a natural hazard.

What is a short term response?

How people react as the disaster happens in the immediate aftermath of the event.

What is a long term response?

The later reactions that occur in the weeks, months and years after the event.

What is monitoring (of earthquakes)?

Looking for signs of an eruption using observation, tiltmeters, GPS, digital cameras on the crater, emission of sulphur dioxide and using robots called ‘spiders’ to look for changes.

What is prediction (of earthquakes)?

Using monitoring of the volcano, past frequency of eruptions, patterns of love flows, ash movements and layers to determine how the volcano is likely to behave to enable effective evacuation.

What is GPS?

Gobal positioning systems use satellites orbiting the earth t detect movements of the land and heat changes.

Define dormant

A volcano that is not currently erupting but is likely to erupt in the future.

What is an active volcano?

a volcano that is erupting or has erupted in recorded history.

What is an extinct volcano?

A volcano that shows no signs of erupting again.

What is a tiltmeter?

a type of technology that detects a change in slope on a volcano caused by shifting magma beneath the surface, predicting eruption.

What is the Pacific ring of fire?

An area where large numbers of earthquakes and volcanic eruptions occur in the basin of the Pacific Ocean. In a 40,000km horseshoe shape, it is associated with a nearly continuous series of oceanic trenches, volcano arcs, and volcanic belts and / or plate movements.

It has 452 volcanos and is home to over 75% of the worlds active and dormant volcanos.

What's aid?

Money, food, training and technology given by richer countries to poorer ones, either to help with an emergency, or to encourage long term development.

What is pyroclastic flow?

A flow of volcanic ash, dust, rocks and debris that Cascades down the slope of a volcano during an eruption. Vry dangerous, reaching speeds greater than 60mph and temperatures in excess of 800 degrees.

What is lahar?

A secondary effect of a volcanic eeruption which are mudflows created by volcanic ash mixing with melted ice or water.

What is a lava bomb?

a block of lava ejected into that air from a volcano. As its thrown out, it cools and spins, causing the block to be rounded.

What is tephra?

A general term for fragments of rock,ash and lava that are blasted into the air by explosions or explosions or carried by hot gases in eruption columns.

What normally causes earthquakes?

Earthquakes usually occur when pressure occur when pressure builds up through friction between 2 plates and then releases suddenly. Therefore, they usually occur at plate margins: either destructive (inc. collision), conservative and sometimes constructive.

What is the place where earthquakes begin called?

The ‘focus’ - this is located deep within the Earth's crust.

Deep-focus earthquakes cause less damage and are felt less than shallow-focus earthquakes as the waves have further to travel so dissipate on their way to the surface.

What is the point directly above the focus on the Earth's surface called?

The epicentre.

What occurs in the epicentre?

This is where shock waves are the strongest and where they radiate out from.

'Primary waves are relatively weak and cause the surface to over forward and backward in the direction of the waves.The stronger ‘secondary waves come next at right angles to the outward movement of the main wave. Both of these travel well below the surface.

The final waves that arrive are those close to the surface and so are more powerful. These involve 2 types, those causing an ‘up and down’ movement called longitudinal waves and those that move at right angles called transverse waves that cause more damage.

What records the extent of the shaking of earthquakes?

Seismographs - record it by the extent of the shaking by a pen identifying the trace of the movement on a rotating drum. The line graph produced is a seismogram.

What is the Richter scale?

This measures the strength or magnitude of the earthquake. There is no upper limit to this scale - it goes as high as the highest earthquake recorded.

Its measured on a logorithmic scale which means there's a 10-fold increase in sie Everytime the scale increases by 1. Therefore a magnitude 5 earthquake is 0x bigger than a magnitude 4 earthquake.

What is the mercalli scale?

This measures the effects of the earthquake in damage. It uses a scale of 1-12 in roman numerals. It uses subjective descriptions of the resulting damage.

When and where did the Haiti earthquake occur?

Port au Prince on the 12th of January 2010 at 4.53 pm.

What was the magnitude of the Haiti earthquake?

7.0

When and where was Italy's earthquake?

L’Aquila. It occured on the 6th April 2009 and 3.32am.

What was the magnitude of Italy earthquake?

6.3

What plates were involved in haitis earthquake?

Nnorth American and Caribbean.

The Caribbean plate moves eastwards by 20mm per year. This fault had been building stress for 250 years. The rupture was 65kms long. The North American plate moves west.

What plates were involved in Italys earthquake?

Eurasian and African.

What type of plate boundary was haitis earthquakes?

conservative.

What type of plate boundary was Italy's earthquakes?

Collision (although a complex region)

The collision has caused the apennine mountains, however in some areas it is pulling apart too. Overall its a continental - continental collision boundary.

What were the primary impacts of the earthquake in Haiti?

230,000 people died.

300,000 injured.

1 million made homeless.

What were the primary impacts of the earthquake in italy?

308 people died.

70,000 made homeless.

1,500 people injured.

What were the secondary impacts of the earthquake in Haiti?

The education system ‘collapsed’ as ½ the schools and all universities were destroyed.

1 in 5 jobs were lost.

What were the secondary impacts of the earthquake in Italy?

1 person died from the trauma of aftershocks

Aftershocks ruptured a drinking water pipe.

What was the immediate response to the earthquake in Haiti?

The Dominican Republic sent 8 mobile medical units with 36 doctors.

American Red Cross raised 7 million in 24 hours.

What was the immediate response to the earthquake in Italy?

40,000 people were in tented camps.

12,000 rescue workers were deployed.

What was the long term response to the earthquake in Haiti?

On the 0th of April, the authorities moved thousands of refugees to a more secure location due to the threat of mudslides and flooding.

US helicopters did ‘food drops.’

What was the long term response to the earthquake in Italy?

Prime minister Silvio Berlusconi refused aid from all countries as Italians are ‘proud people'. They did, however, take money from the US for rebuilding.

Did scientists predict Haiti's earthquake?

No, although they were using gPS to monitor movement each year. In 2008, they said an earthquake of 7.0 magnitude or higher would be likely.

Did scientists predict Italy’s earthquake?

An italian laboratory technician predicted a major earthquake 1 month before it occured on TV. He was accused of being an alarmist and forced to retract it.

Did people protect against Haiti's earthquake?

No - buildings were poorly built as there are no construction codes.

Did people protect against Italy’s earthquake?

They had supposed ‘earthquake proof’ buildings such as the hospital and university, but these were severely damaged.

Did people prepare for Haiti's earthquake?

No - they have other hazards they're aware of, such as hurricanes, but aren't prepared for earthquakes.

Did people prepare for Italy’s earthquake?

Earthquakes are a regular occurrence in Italy, however large ones are relatively infrequent.

L'Aquila is built on the bed of an ancient lake, providing a soil structure that amplifies seismic waves. So, under prepared considering this.

Can earthquakes be predicted?

Its possible to predict their general location but its extremely difficult to predict their time, date and exact location.

Can volcanoes be predicted?

They're easier to predict than earthquakes. They usually give some signs if they're about to errupts, but the exact time and date of the eeruption is still difficult.

How do automatic shutters coming down over windows reduce the negative effects of earthquakes?

It reduces the risk of glass shattering and falling.

How do open areas outside near buildings reduce the negative effects of earthquakes?

Can be used to help evacuations.

Prevents the building from causing more damage if they fall.

How do rubber shock absorbers in the foundations reduce the negative effects of earthquakes?

They absorb the ground shaking.

How can the government reduce the risks of living in earthquake prone areas?

They can spend money on earthquake proof infrastructure and create training schemes to provide civilians with knowledge on what to do if they occur.

Why do people choose to live in hazardous areas?

People in poverty have other concerns such as money and food.

Plate margins often coincide with very favorable areas for settlement, such as coastal areas where ports have developed.

Volcanoes can bring benefits such as fertile soils, rocks for building, rich mineral deposits and hot water.

Better building design can withstand earthquakes so people feel less at risk.

Why does tourism encourage locals to stay in hazardous areas?

Tourists visit volcanos for spectacular and unique views, relaxing hot springs, and adventure. More than 100 million people a year visit volcanic sites every year. The revenue they generated benefits the locals and the countries they're in.

What is an example of planning for an earthquake?

Preparing emergency aid supplies, how they would be distributed and where evacuation centres will be. This helps saves lives as food, water, medicine and shelter are accessed.