Earthquakes and Volcanoes Flashcards
Where are earthquakes found?
- Tectonic plate boundaries
- In linear patterns
- Along coasts of continents
- The pacific ring of fire
Where are volcanoes found?
And in what arrangements
- Tectonic plate boundaries
- In linear patterns
- Along coasts of continents
- Hotspots such as Hawaii
- The pacific ring of fire
What are the layers of the earth?
1) Crust
2) Mantle
3) Outer core
4) Inner core
What are the characteristics of the Crust?
- Thin (10 - 70km)
- Composed of earth, rock & water
- Constantly moving
What are the characteristics of the Mantle?
- Composed of Semi-molten rock
- Heat currents (convection currents constantly rise & fall)
What are the characteristics of the Outer Core?
- Composed of molten metals at extremely high temperatures
- Liquid
What are the characteristics of the Inner Core?
- Composed of metals at extremely high temperatures
- Solid due to extreme pressure
What makes tectonic plates move?
Convection currents (heat currents inside the mantle that rise and fall)
How much do tectonic plates move per year?
1 - 2 inches
What are the 2 types of crust (earth’s surface layer)
1) Oceanic crust
2) Continental crust
What are the 4 types of plate boundaries and when do they occur?
Constructive/divergent:
- 2 plates moving apart
Destructive/convergent:
- 2 plates moving towards each other one oceanic and one continental)
Collision/convergent
- 2 plates moving towards each other, both continental
Conservative/transform
- 2 plates moving side by side (can be opposite or the same direction)
Describe the process of Constructive/Divergent plate boundaries
- Do volcanoes or earthquakes occur?
- Why does this occur?
- What features are formed?
- Give an example
Constructive plate boundaries occur when two tectonic plates move apart.
This forms volcanoes because the proces has no risk of plates locking with each other, but lava wells up through the gap left between the two plates.
On land, a ridge can be formed. Under water, because the plates are much thinner, lave wells tup though the gap and cools down to create Underwater mountains and ridges. These can grow and form an island.
An example is Iceland, which is sitting on two tectonic plates and growing.
Describe the process of destructive/convergent plate boundaries
- Do volcanoes or earthquakes occur?
- Why does this occur?
- What features are formed?
- Give an example
Destructive plate boundaries occur when two tectonic plates (one oceanic and one continental) move together, and the oceanic one subducts under the continental one because it is denser.
This forms explosive volcanoes and earthquakes because the plates can sometimes lock together, and friction builds. A sudden release of this friction can create an earthquake.
As the oceanic crust subducts, it melts due to the pressure and heat. This magma rises into a magma pocket and erupts on the continental plate, forming a volcano.
The compression exerted on the continental crust can create fold mountains.
An example is the Nazca plate converging with the Andes mountain range, the second largest mountain range in the world.
Describe the process of Collision/Convergent plate boundaries
- Do volcanoes or earthquakes occur?
- Why does this occur?
- What features are formed?
- Give an example
Collision plate boundaries occur when two tectonic plates (both continental) move together, and they both move upwards due to similar densities.
This forms powerful earthquakes because the plates compress each other, and friction builds. A sudden release of this friction can create an earthquake.
The compression exerted on the continental crusts causes them both to rise and create extremely high mountains.
An example is the Himalayas, which is a large mountain range, containing some of the highest mountains in the world.
Describe the process of Conservative/Transform plate boundaries?
- Do volcanoes or earthquakes occur?
- Why does this occur?
- What features are formed?
- Give an example
Conservative plate boundaries occur when two tectonic plates slide/rub agains each other, going in the sam or opposite directions.
This forms powerful earthquakes because as the plates move, thay can lock together. This creates a lot of friction, and when this friction is released, the sudden movement creates huge earthquakes.
This can also form a ridge, and can be quite spectacular.
An example is the San Andreas Fault, which is probably going to create another earthquake soon.
What is a hotspot?
An unusually hot plume of magma in the mantle
Describe the formation of the Hawaii island chain
1) An unusually hot plume of water rises from the mantle (hotspot)
2) The magma melts the crust and erupts underwater, creating an underwater volcano
3) Continuous eruptions add repetitively to the volcano’s size, until it rises above water and becomes an island. It ontinues growing as long as it remains active
4) As the hotspot is stationary, but the tectonic plate is moving, the volcanoes eventually drift off the hotspot and become extinct
5) Over time, the island/former volcano erodes from weathering and erosion processes
When did Eyafjallajökull erupt? How many years ago was the eruption before the most recent one?
2010, had not erupted for 180 years
How many years of volcanic unrest had there been before the Eyafjallajökull eruption?
18
How can volcanic activity be monitored?
- GPS technology (to see if the land has changed shape slightly)
- Seismic monitoring, to detect and tremors that might signify a volcanic eruption
- Spectrometers (measure amound of sulfur dioxide)
Why did Eyafjallajökull erupt with 2 different types of magma? What types of magma was it?
2 seperate sources of magma were acumulating in the same place. Which reacted together, creating an unexpectantly large explosion
Basalt and silica-rich andesite.
When was the first eruption of Eyafjallajökull, and what happened?
March 20th 2010, magma spews onto an unhabited region
When was the second eruption of Eyafjallajökull, and what happened? Were there any consequences?
April 14th, a huge glacial flood (heat partially melts glacier) causs evacuation of 800 people. It also threw volcanic ash several kilometres into the atmosphere. The ash cloud spread, stopping air transport in northwest europe.
What did Eyafjallajökull measure on the volcanic explosivity index?
4
Why do people live near volcanoes despite the risk?
- Geothermal energy (and HEP for Iceland)
- Tourism (jobs)
- Fertile soils
- Volcanoes monitored/effective management
- They don’t erupt that often
How long did the Eyafjallajökull last?
7 months
How many deaths did the Eyafjallajökull eruption cause? Why?
0
Due do effective management
What were the effects of the Eyafjallajökull eruption within iceland?
- Areas were flooded because of the glacier melt water which lay above the volcano.
- Agricultural land was damaged, and farms were hit by heavy ash fall.
- The ash fall poisoned animals in nearby farms.
Some roads were destroyed. - People were asked to stay indoors because of the ash in the air.
What were the effects of the Eyafjallajökull eruption within Europe?
- Travel was severely disrupted as many flights were cancelled between 14 and 21 April 2010
- The eruption produced 0.3 cubic kilometres of ash, which resulted in the disruption of 95,000 flights across Europe and economic losses of 5 billion euros.
- Businesses lost trade.
- Air operators lost millions of pounds each day.
- Perishable foods were wasted as they could not be transported.
- People were not able to get to work because they were stranded.
- The timing of the disruption was during the Easter holidays when levels of tourism are high.
What are the causes of the Eyjafjallajötkull eruption?
Iceland is on a hotspot and on a divergent plate boundary. The plates move from 1 - 5cm per year.
What are the benefits of volcanoes:
- Eruption brings tourism
- Ash brings fertile land
- Geothermal energy
How did the Icelandic government manage the Eyjafjallajökull eruption?
- European red cross mobilised staff and volunteers and other resources to help people affected by the volcano.
- The area around the volcano was evacuated.
- Rivers were partially deviated to not harm bridges
Def. Earthquake
Shaking and vibration of the ground caused by movements in the earth’s crust
Def. Fault
A weak point in a tectonic plate where pressure within the crust is released
Def. Epicenter
The point on the ground above the focus where the vibration is the greatest
Def. Magnitude
The strength of an earthquake
Def. Focus
The point underground that shock waves travel out from
What is the Mercalli scale?
Earthquakes were initially measure using the Mercalli Scale (1906). This was a measurement of peoples observations, and not very accurate scientifically
What is the Richter Scale
In 1934, the Richter Scale was created, which measures earthquakes via measurement of the largest seismic wave. It is exponential, meaning each stage releases 32 times more energy than the last
What is the Moment Magnitude scale?
1979, the Moment Magnitude Scale is created, which uses pretty much the same system and numbers than the Richter Scale, but measures the Geometry of the land and the rupture of the fault in addition to monitoring seismic waves. It is the most widespread now.
What was the magnitude of the Turkey earthquake?
And it’s aftershock
7.8 (aftershock was 7.5)
What caused the Turkey earthquake?
- Convection currents move tectonic plates
- Turkey is on the small anatolian plate
- Anatolian plate is being crushed by the Arabian Plate from the southeast and the Eurasian Plate in the Northeast
- This movement squeezes the Anatolian plate to the west
- East Anatolian fault was building up pressure
When was the Turkey earthquake?
Feb 2023
What were the impacts of the Turkey earthquake?
- 50,000 deaths across SE Turkey and NW Syria
- 6500 buildings in Turkey collapsed across 10 cities, including a 1,700 year old castle in the city of Gaziantep.
- At least 2 million left homeless across SE Turkey and NW Syria.
- People left to fend for themselves with many camped out in makeshift shelters
Why were the effects of the Turkey earthquake so devastating?
- Multiple aftershocks after major earthquake
- Earthquake struck close to densely poulated areas, killing more people and the main cause of death was buildings
- Bad building codes, corruption, old buildings had not been retrofitted
- Earthquake struck around 4 am, meanng people were sleeping and didn’t realise the earthquake was coming to shelter themselves until it was too late.
- The area lacked proper preparation as the area had not had an earthquake since 1800.
- Slow emergenc response
- War in Syria made it hard to help
- Winter, conditions below 0
Def. Volcanic bomb
Pieces of rock flung out of a volcano during an eruption
Def. Pyroclastic flow
Column of hot ash and rock running down the flanks of a volcano
Def. Ash cloud
Cloud of hot volcanic material that has exploded into the atmosphere
Def. Lahar
When volcanic ash and mud mixes with water it forms a mudflow called a lahar
Def. Fumaroles
A hole in a volcanic area from which hot smoke and gases escape
Def. Tephra
Small pieces of rock and ash
Def. Magma chamber
A larger reservoir in the crust of the earth that is occupied by a body of magma
Def. Conduit
Main artery through which magma flows inside a volcano
Def. Lava Dome
A build-up of lava on the side of a volcano that may erupt to form a second crater
Def. Crater
A Large opening in a volcanic mountain created by an intense volcanic explosion
Def. Vent
Opening in the earth’s crust through which lava escapes
Def. Lava flow
A stream of molten rock that is released from a volcano
How many volcanoes erupt every year?
20 - 30
per year
Describe a volcanic eruption
- Volcanoes are mountains that have been built up from layers of ash and lava that come out of hotter parts of the earth.
- Most volcanoes are cone shaped and look like mountains, but they have a vent (a hole in the middle through which lava and ash can spew out.)
- When a volcano erupts melted rock is forced out by pressurised gas.
- Lava flows can be fast or slow, depending on the type of melted rock. Some is thick and stiff and other lava is thin and runny.
- Small pieces of rock and ash (tephra) can be carried great distances by the wind.
- Some volcanoes don’t erupt with lava at all, instead they shoot out chunks of rock called volcanic bombs
What are the features of shield volcanoes?
- Usually occurs on a constructive plate boudary
- Shield volcanoes have gently sloping sides and are formed from layers of lava.
- Eruptions are typically non-explosive.
- Shield volcanoes produce fast flowing fluid lava that can flow for many miles.
- Examples of shield volcanoes include the Hawaiian volcanoes.
- Although these eruptions destroy property, death or injury to humans rarely occurs
Describe the formation of a shield volcano
- Shield volcanoes have very runny lava (they are not viscous); because of this they do not have an ‘explosive’ eruption.
- Lava spreads quickly across the landscape
- With each eruption a new layer of rock is built on the previous one. Gradually a wide dome of rock is built up.
- It is called a shield volcano because it looks like a curved shield lying on the ground (or an upside down dinner plate). The slopes of a shield volcano are very gentle. The Hawaiian islands are a chain of shield volcanoes
What are the features of composite volcanoes?
- Usually occurs on destructive plate boundary
- Composite volcanoes, sometimes known as stratovolcanoes, are steep sided cones formed from layers of ash and lava flows.
- Composite volcanoes can rise over 8000 feet.
- Examples of composite volcanoes include Mount Fuji (Japan), Mount St Helens (USA), Mount Vesuvius (Italy) and Mount Pinatubo (Philippines).
- When composite volcanoes erupt they are explosive and pose a threat to nearby life and property.
Describe the formation of a composite volcano
- They are formed by hardened layers of lava and ash from successive eruptions.
- The lava is viscous (therefore thicker than with shield volcanoes) and it cools and hardens before spreading very far – this makes the volcano steep sided.
- The eruptions tend to be very violent.
- Mount Vesuvius in Italy is an example of a Composite Volcano.
Summarize the differences between shield and composite volcanoes
- Shield volcanoes are wide whereas composite volcanoes are tall.
- Shield volcanoes have gently sloping sides whereas composite volcanoes have steep sides.
- Shield volcanoes produce thin, runny (non-viscous) lava whereas composite volcanoes produce thick, sticky, (viscous) lava
- Shield volcano eruptions are less explosive than composite volcanoes
What can be done to manage the risk in earhquake zones?
- Prediction - forecasting whether an earthquake will happen
- Prevention - trying to limit damage and loss of life
- Can be predicted by early warning systems that give people messages 20s -1min in advance (Mexico and Turkey have invested in these, but they are very expensive)
- To do this, seismometers detects movements in the earths crust
- It is also important to educate the population with earthquake drills
- Ask population to prepare emergency kits
- Implimenting earthquake resistant building design, such as rubber shock absorbers
