Tectonic activity and hazards

Overview of exam:

You will sit an exam for 1 hour and a half, the paper will be out of 70 marks and it will be in the format of an essay-style report. This is used to show the depth and quality of your understanding of the chosen topic (I will only be covering tectonic activity and hazards).

Despite the early release date, I personally will be constantly adding new up to date/ relevant case studies and you should too.  No information is available about the pre-release but I may release an extra document in relation to guesses and approaches.

 

Also, throughout research you need to link the global synoptic context which I will go into more detail later, how to connect to each piece of research, examples and how to link to the report.

Global synoptic context

This focuses on the PLACES, PEOPLE and PLAYERS. When gathering research, you should be aware of these three linked components. Their importance will vary depending on the key question you are researched.

Tectonic hazards and causes

Explain the difference between a tectonic event, hazard and a disaster.

A tectonic event is a physical occurrence resulting from the movement of the Earth’s crust. They are predominantly earthquakes and volcanic eruptions.

A tectonic hazard is when they have the potential to cause loss of life and damage to property.

A tectonic disaster is (according to the UNISDR):

• 10+ people are killed
• 100+ people are injured
• International aid is called for
• A state of emergency is declared

You need to make sure your report is factually correct and well-structured in order to stand as tectonic activity and hazards is one of the most popular units.

Make sure you learn the facts and figures for a range of up-to-date (within the last 10 years) examples of tectonic hazards and disasters.

You can use older case studies, but there needs to be a good justification for this.

Describe and illustrate the threats from a range of volcanoes and earthquakes.

Volcanoes

• Lava flows- this is when liquid rock is expelled from the crown of the volcano. Depending on the viscosity of the lava, depends on the rate of movement of the lava. The viscosity, in itself is influenced by the temperature, the silica content and the volcano’s slope.

What is silica content?

Silica is SiO₂ –silicon and oxygen. Silicon and oxygen are the most abundant (common) dissolved gases in magma.

Magma varies from mafic magma (low silica content and high Fe and Mg) and felsic magma (high silica content and low Fe and Mg).

What is viscosity?

Viscosity is the consistency of a substance; the ability to resist flow. The higher the temperature of magma lowers the viscosity.

What does this have to do with volcanic eruptions?

Viscosity increases with increasing silica content due to silica chains. High viscosity lava (mafic magma) flows slowly and covers a small area. This is in contrast due to low viscosity lava which flows quickly and covers a large area.

E.g. Hawaii’s volcanoes have high viscosity lava and so despite the most active volcano being located there, there aren’t many deaths because of the felsic magma. People can outrun the lava flows and so are not killed by it due to the high viscosity.

• Explosive blasts-examples of these include tephra and lava. The blast cloud is more destructive than the rock debris that is released.
• Ash flows– dense masses of gas and fragments of lava flow down the sides of the volcano. This occurs when gas-saturated lava comes near the surface of the Earth. As the pressure falls (when released from the volcano), the gas forms bubbles which break lava into ash. If the ratio of gas to ash is low then the ash can pull the gas down into pyroclastic flows.
• Ash falls-they are very disruptive. The heavy ash can collapse roofs cover branches and leaves.
• Mudflows-this occurs with large deposits of ice and snow. As melt water flows it mixes with loose soil and ash. This is also known as a lahar.
• Glacial outbursts-masses of water/ice are released from a glacier because of the heat of the volcano. It can turn into mudflows.

Earthquakes

• Ground displacement-the impact on buildings can be life threatening and infrastructure can be affected. Secondary impacts include water pipes and electricity/gas damage.
• Landslides-movements of masses of rock, Earth or debris. Slope failure may occur because of earthquake tremors or heavy rain.
• Liquefaction-this occurs when shaking of the silts, sands and gravel cause them to lose their load-bearing capacity. A consequence from this leads to structures sinking.
• Tsunamis-ocean waves with extremely love wavelengths generated by earthquake tremors.

What are the factors of hazard profiles and what do they reveal?

1. Frequency- this usually suggests that a larger amount of hazards occur with a lower magnitude. This is rather than high magnitude earthquakes which are infrequent. If there is a high frequency of tectonics, they are less likely to be high in magnitude because the pressure has been released in earlier tectonics.
2. Magnitude-this is the opposite of frequency. High magnitude tectonic hazards are less likely to happen frequently because of the amount of time taken to build up the pressure.
3. Duration-this is measured by the time taken for the fault to rupture.
4. Areal extent-the surrounding area that is directly affected. This varies depending on the magnitude and location of the hazard.
5. Speed of onset-this is time taken for the tectonic event to take effect.

E.g. the super volcano Yellowstone would take over a year to erupt.

What is the world’s deadliest tectonic disaster?

LOCATION: Shaaxi, central China.

DEATHS: 1 million.

TIME: N/A

MAGNITUDE: 8.0.

DATE: January 1556.

What was the reason for the amount of deaths?

People live in caves because of the climate: hot in the summer and cold in the winter. The caves are created from soil and so are perfect for the conditions of the climate. However, the soil is soft and so highly fragile, when the shockwaves hit, the caves were destroyed.

1300 square metres was destroyed, the earthquake also create new valleys and hills.

This disaster could occur again as 40 million people live there; the amount of deaths could be worse.

How are tectonic events measured?

The Richter scale-it is calculated from the amplitude of the largest seismic wave recorded during the event. It is a 10 logarithmic scale.

The Mercalli scale-this measures the intensity; it quantifies the effect of earthquakes.

Volcanic explosivity index-this measures the volume of debris (as an example) of a volcano.

What is the world’s costliest tectonic disaster?

Sendai, Japan (2011)

DIRECT LOSS- $210 billion and 20,000 dead.

RECONSTRUCTION-$244 billion

What are the causes of tectonic hazards/events?

 

The asthenosphere is heated by radioactive decay (of elements such as Uranium). As the radioactive source is heating the asthenosphere, the fluid/ plastic magma circulates because of the convection current leading to plate tectonics.

Assess evidence for the theory of plate tectonics.

The asthenosphere is heated by radioactive decay (of elements such as Uranium). As the radioactive source is heating the asthenosphere, the fluid magma circulates because of the convection currents leading to plate tectonics.

Alfred Wegner (1912) published the theory ‘Continental Drift’. This explained 300 million years ago, there was a single continent (Pangaea). This further split into Laurasia and Gondwanaland.

Evidence

Molten lava is magnetic, when it is liquid; it wants to align with poles. Some rocks are aligned opposite (magnetic field has changed). There are patterns 1000kms away symmetrically suggests they were once together. Other evidence includes Fossil Records, Geological matching and jigsaw fit of the continents.

Professor Iain Stewart suggests the Mediterranean is closing (just as the Tephras Ocean did because of the formation of Eurasia and India when the Himalayas formed). This is because Africa is colliding with Southern Italy, it is shown in Mount Stromboli (Italy’s most active volcano).

Types of plate boundaries on a tectonic map

You need to know the structure of the Earth and the location of the major tectonic plates and plate boundaries.

 

The Wilson Cycle:

The Wilson cycle is just an extension of continental drift/plate tectonics and the rock cycle. It describes the birth, life, and death of Earth’s oceans. Most of Earth’s oceans are in one of these three stages.The Wilson cycle states that the present continents were once joined (Pangea), and that this process of coming together and splitting apart has occurred 6 – 10 times throughout the geologic history of the Earth. The Wilson cycle describes ocean basins, and the stages that they go through from creation to extinction in 6 separate stages:

Embryonic: Thick continental crust blocks the flow of heat, and there is a change in convection currents of the asthenosphere (the soft plastic layer on which the continental and ocean plates ‘float’). There is an upwelling of magma, which causes continental rifting to begin. The East African rift valley system is an example of this process.

Youth: The rift expands as magma continues to rise to the surface and creates new crust, and water fills the young ocean basin, creating a ‘linear ocean’ like the modern Red Sea.

Adolescence: The new ocean grows wider and begins to age. The passive boundaries between the continent and the oceans are accumulating sediment from the erosion of the continents. The Atlantic Ocean is one such maturing ocean basin.

Maturity: The weight of accumulating sediments at the margin where continental crust meets the ocean basin causes depression and a subduction zone, where the thinner, dense ocean crust slips below the continental crust. The Pacific Ocean as an example of this stage in ocean development. 

Old Age: Accretionary wedges are formed as sediments are scraped off the subducting ocean crust which creates a tectonic crest which can form offshore island arcs. The ocean basin continues to narrow. This terminal stage of development is exemplified by the Mediterranean Sea.

Death: All of the oceanic crust that separated the two masses of continental crust has been subducted, and the continents collide. This collision causes a mountain range to form along the collision face. Examples are the Himalayas where India collided with Asia, and the Ural mountains which mark the collision of the Asian landmass with Europe.

Illustrate the different types of plate boundary: convergent, divergent and transform

Convergent

Convergent is the new term for destructive (GCSE term) plate boundary.

• The plates move towards each other.
• Due to descending convection currents in the mantle.

The oceanic crust is denser than continental crust and so when they converge the oceanic plate is subducted in the asthenosphere beneath the continental plate. This melts approximately 100km below the surface. The melted surface (the oceanic crust) is less dense (now) and so it rises through weaknesses in faults and plate boundaries. It can cool forming intrusive (molten into cracks or between layers of rocks) igneous rocks, e.g. granite. Or it may form a violent volcanic eruption. Earthquakes are also common at the Benioff zone where the plates get locked due to the pressure and break away after the release.

E.g. the Philippines and Pacific plate tectonic movement in the August 2012 earthquake and September 2013 earthquake.

The Philippines

100% of the Philippines are at risk from earthquakes.

• October 2013 earthquake.
• EMERGENCY RESPONSE-Tsunami evacuation because of the 2004 Asian Ocean tsunami, it was issued from Indonesia to Japan. Officials advised residents to move to higher level. Many moved to evacuation centres even after the tsunami warning was lifted.
• HUMAN IMPACTS-10 people were killed. $3 million infrastructure damage with power cuts in Visayas and Mindanao. Houses are collapsed and minor damage to buildings and bridges.
• PHYSICAL IMPACTS-Small tsunami generated (16cm) according to the Pacific Tsunami Warning Center.
• LOCATION-Samar Island, Philippines
• TIME-20:47
• MAGNITUDE-7.6
• August 2012 earthquake.
• Mount Mayon eruption
• LOCATION-Luzon Island, Philippines
• PHYSICAL IMPACTS-It produced Strombolian and Vulcanian eruptions. Rivers of rholitic lava, 2,000 eruptions and 6,000 tonnes of sulphur dioxide released (on average it is usually 500 tonnes). Lava fountains rose 650ft.
• HUMAN IMPACTS-there was $1,400,000 from humanitarian aid and NGOs. Ignorance-3000 people refused to evacuate. There was ash fall in the Albay province.
• EMERGENCY RESPONSE-40,000 people were evacuated and a 5 mile exclusion zone was set up. Power and water cut to discourage residents; commission of human rights allowed authorities. UN food brought high-energy biscuits in. UK, USA and Canada advised people not to visit.
• October 2013 earthquake

Christchurch, 2011

• MAGNITUDE-6.3
• TIME-12:51
• LOCATION-New Zealand
• PHYSICAL IMPACTS-it was a previously unknown strike-slip fault and liquefaction was widespread: elevated by rupturing water pipes.
• HUMAN IMPACTS-$16 NZ, half of buildings were destroyed and the Canterbury Christchurch television building killed 85 people.
• TECTONIC PROOF-the AMI stadium had strengthened foundations as a result of the September 2010 earthquake but it did not withstand. Geonet detects earthquakes and the Earthquake Commission was established to provide insurance.  Older buildings were reinforced in the North Island of New Zealand but not on the South Island where the earthquake occurred-not in a common tectonically active area.
• EMERGENCY RESPONSE-Canterbury Earthquake Recovery was established.

 

Divergent

Divergent is the new term for constructive (GCSE term) plate boundary.

• Plates are moving away from each other.
• Due to the two convection currents diverging beneath the surface which leads to magma from the mantle brought up to the surface.

There was pressure from the rising magma which led to a doming of the surface and the formation of a ridge. As the plates move apart, faults are produced in which magma can rise through. Rising magma cools and solidifies producing new crust: within the existing crust or following a volcanic eruption.

• Most earthquakes are shallow, low magnitude and high frequency. This is because of the closeness to the surface and the pressure is easily released when plates diverge.

Iceland.

• Eyjafjallajoekull eruption, March/April 2010

This could often lead to Katla’s eruption and this is usually followed historically.

It produced Strombolian eruptions.

• PHYSICAL IMPACTS-In the 2^nd eruption, there was a 1km fissure caused flooding (because it was a glacier covered vent). This raised rivers by 3m and there was a 27 storey tall of lava released.
• HUMAN IMPACTS-104mg of fluorine per kilogram of ash, this had an effect on livestock: renal and hepatic effects. Infrastructure was severely disrupted-transport.
• GLOBAL IMPACTS-the airspace passing Iceland was
• EMERGENCY RESPONSE-Tsunami evacuation because of the 2004 Asian Ocean tsunami, it was issued from Indonesia to Japan. Officials advised residents to move to higher level. Many moved to evacuation centres even after the tsunami warning was lifted.

Transform

 

Transform is the new term for conservative (GCSE term) plate boundary.

• No magma is released; no magma is destroyed by subduction.
• No new crust is formed.
• Can produce both shallow earthquakes and high magnitude earthquakes.

Haiti

• January 2010 earthquake.
• Slip of Enriquillo Plaintain Garden fault (locked for 200 years)
• MAGNITUDE-7
• TIME-16:53
• LOCATION-Port-au-Prince (capital and most densely populated area), Haiti
• PHYSICAL IMPACTS-5.9 aftershock, 20 million m³ of rubble-5% cleared
• HUMAN IMPACTS-230,000 dead, 1 million homeless and 3 million people affected. Small businesses were essential for Haiti’s economy and they lost everything, they couldn’t afford the rent after the damage but there are still 100,000 reusable buildings. 1/5 jobs lost and ½ million remained in tents-Oxfam-January 2012. 80% live below the poverty line, the US sent $5.8 billion in relief but half was paid as debt.
• INTERNATIONAL AID/RESPONSE-Dominican Republic was the first and sent an emergency team, heavy machinery, food and water. ICE-SAR (Icelandic Search and Rescue team) arrived 24 hours late due to a hold up at the airport. Qatar sent a strategic transport with 50 tonnes of relief. American Red Cross ran out of supplies. Housing is not prioritised by the government and only by NGOs.

Suffered a cholera epidemic not as a secondary effect but because of the disaster-loss-recovery cycle.

Collision

• Two continental plates collide and are crushed against each other. They are pushed upwards to form new mountains.

 

Baluchistan, Pakistan

• 24^th September 2013
• Formation of a 200m island.
• MAGNITUDE- was 7. 0
• LOCATION-Baluchistan, Pakistan
• PHYSICAL IMPACTS-a 200m island appeared off the coast of Gwadar.
• HUMAN IMPACTS-328 dead, 300,000 affected over 6 districts and 90% of houses were destroyed.
• INTERNATIONAL AID/RESPONSE-Pakistan’s troops were the first to respond, 200 soldiers and medical teams from Quetta.
• Make sure you know what happens at each of the four types of plate boundary and whether volcanoes, earthquakes or both occur.

Tectonic hazard physical impacts

EXTRUSIVE IGNEOUS ACTIVITY-This is the production of different landforms created by material outpouring from the Earth’s crust.

This includes lava plateaus, volcanic cones and fissures.

The distribution of extrusive igneous activity is dependent on the pattern of the plate boundaries (convergent, divergent and transform) and hot spots.

Their impact on the landscape depends on the magnitude, the scale of the event causing them and the types of material extruded.

Major extrusive igneous activity

Lava plateaus

This is usually an extensive area of basaltic (mafic) lava, often covered with a layered surface. Lava plateaus are formed by eruptions from vents or fissures. The layered surface is caused by the accumulation of lava from a series of eruptions. The plateau tends to be flat, with limited soil and vegetation cover.

Reminder of mafic/basaltic lava

They are produced from:

• Shield volcanoes
• Fissures
• Cinder/scoria cones

 

Basaltic	Andesitic	Rholitic
Takes longer to cool and solidify.	In the middle.	Quick to solidify and cool.
Low silica content.		High silica content.
High maintenance of temperature-1200 degrees Celsius.		Cooler than basaltic-800 degrees Celsius.
Lava and steam ejected.		Ash, rocks, gases, steam and lava is ejected.
Eruptions are frequent due to the lack of pressure built up. E.g. shield volcanoes		Eruptions are less frequent but more violent due to the build-up of gases and increased pressure. E.g. composite/stratovolcanoes.

 

Pahoehoe lava is typically the first lava to erupt from a vent. This type of magma is thin (1-2 m) and very fluid with a low viscosity (high Fe and Mg content, low Silica content).  As Pahoehoe lava cools, it turns to a dark grey colour and become less fluid and more viscous (higher Silica content).

Pahoehoe lava is often converted to a ’a lava when the lava advances away from the volcano. The conversion of a’a to pahoehoe rarely takes place.

Example: Columbia plateau, USA

The Columbia plateau is surrounded by one of the world’s largest accumulation of lava.  It was produced by Icelandic

The Snake River plain stretches across Oregon to Wyoming (to the location of Yellowstone).

Cinder cones surround the landscape of the Snake River Plain. Some are aligned along vents, calderas: plugs/pits formed from large volcanic eruptions, low shield volcanoes and rhyolite hills. Many of the extrusive igneous activity landscapes located at the Columbia plateau are obscured by recent lava flows.

It was created by a fissure eruption (usually created at divergent plate boundaries).

 Volcano types

Volcano type	Volcano shape	Composition	Plate boundary	Example
Calderas	Steep depression			Yellowstone, Wyoming, USA
Cinder/scoria cones	Straight sides with steep slopes. Large crater.	Tephra. Occasionally andesitic.	Hot spot.	El Jorullo, Mexico
Composite/stratovolcano	Steep upper slopes with gentle lower slopes. Small crater.	Alternating lava from basaltic to rholitic and tephra (ash). Overall andesitic composition.	Convergent.	Mount Mayon, Philippines.
Dome volcano	Very steep sided.	Acid lava (very rholitic).		Chaiten caldera, Michinmakiida volcano, Chile
Mud volcano	Associated with areas of declining volcanic activity. Hot mud mixes with surface deposits.	Mud.		Mount Lusi volcano, Indonesia
Shield volcano	Gentle slopes. Broad, low-profile volcano.	Basaltic (mafic) lava flows.	Divergent. Eruptions are frequent and low in magnitude.	Mauna Loa, Hawaii.

Calderas- shown in volcano types.

This is when the build-up of gases become extreme, explosions may clear the magma chamber.

There are three types of calderas: crater-lake caldera (created by stratovolcanoes), resurgent calderas and basaltic calderas (shield volcanoes).

Cinder cones- shown in volcano types.

• Most common type of volcano.
• Smallest, generally less than 300km.
• Occurs in basaltic lava fields or parasitic cones on stratovolcanoes or shield volcanoes.

Example: El Jorullo, Mexico

It was formed by the Trans-Mexican volcanic belt due to the subduction of the Cocos plate and the North American plate. It was 1000km in length from the Pacific Ocean to the Gulf of Mexico. It produces Strombolian eruptions.

Dome volcanoes

Acid lava solidifies quickly when exposed to air. It is very steep sided, solidifies near the centre.

Example: Chaiten caldera, Michinmakiida Volcano, Chile

• Before the 2008 eruption, it consisted mainly of a rholitic lava dome.
• In May 2008, it began erupting violently producing lahars and pyroclastic flows. It also built a lava dome.
• Located on the convergent Nazca and South American plate.
• It affected travel and agriculture in surrounding areas.

Mud volcanoes

They are often associated with areas of declining volcanic activity. Hot mud mixes with surface deposits.

Example: Mount Lusi, Indonesia

• Left 13,000 homeless.
• Buried homes, schools and farmlands over 7km².
• Unknown causes: 6.3 magnitude earthquake and/or drilling of the area.
• It is suggested to last 26 years.
• 50,000 people have been displaced.
• Erupted through a 50m central vent.

Shield volcanoes

Example:  Mauna Loa, Hawaii

• It was created via a hot spot: areas where the crust is particularly thin or weak; where the magma rises from the asthenosphere.
• Originally formed under the Pacific Ocean by ejected basaltic lava.
• World’s largest active volcano.
• There is a caldera, Mokuaweoweo, at the summit.

Stratovolcanoes (also known as composite volcanoes) – shown in volcano types.

The composition of ash is lava-ash with a small summit crater.

Example: Mount Mayon, Philippines—located in the Philippines case study.

Fissure eruptions

When two plates move apart, lava maybe ejected through fissures rather than via a central vent.

Example: Columbia Plateau, USA

Case study in lava plateaus. The Columbia Plateau was created via a fissure eruption.

Types of eruptions

1. Icelandic-created from a fissure releasing basaltic lava with great volumes of lava. E.g. Columbia Plateau, USA.
2. Hawaiian-created from a fissure/hotspot/caldera with quiet/moderately active eruptions and minor amounts of ash.
3. Strombolian-this is usually from stratovolcanoes/composite cones and has moderate/rhythmic explosions, the lava is usually in clots and there is more intense activity with light coloured clouds which reach moderate heights.
4. Vulcanian-the lava is more viscous with a gas build-up, dark ash-laden clouds and depositing tephra.
5. Vesuvian-extremely violent with gas-saturated magma and the eruption is after an interval of mild activity, there is tephra and clouds of ash.
6. Plinian-this is the last phase of an eruption: high volumes of gas, narrow at base and low in tephra.
7. Pelean-high viscous lava with a delayed explosive and it is usually blocked by a plug.
8. Katmalian-massive ash flows, explosive tephra, hot springs and fumaroles.

Minor extrusive igneous activity

Solfatara

Created when gas mainly sulphur dioxide escapes onto the surface.

Research point-sulphur is yellow, so if you come across a minor extrusive activity then it is highly likely to be a solfatara.

Example: Solfatara Volcano, Italy

It is a semi-active volcano that exhales sulphurous vapours and gives vent to liquid mud and hot mineral springs.

Geysers

Water in the lithosphere is heated by rocks and turns into steam and water explodes onto the surface.

Example: Old Faithful geyser (Yellowstone), California, USA

Geysers require exact conditions. These conditions include a natural deep subterranean supply of water, a source of heat and a series of fissures, fractures and cavities that provide a path to the surface of the earth. This particular geyser is heated by the transform plate boundary’s magma flow: North American and Pacific Plate. This is also the reason of the formation of the supervolcano Yellowstone.

Fumaroles

Superheated water turns into steam as the pressure drops when it emerges from the ground.

Example: Valley of Ten Thousand Smokes, Alaska

The valley was created in 1912 by the eruption of the Novarupta and Mount Katmai volcanoes. There was tens of thousands of jets of steam and gas ranging up to 1,200° F (649° C) issuing from vents in the Earth up to 150 feet (46 m) across. Over more than 40 of the valley’s 56 square miles lay a covering of ash up to 700 feet (210 m) in depth.

Intrusive igneous activity

INTRUSIVE IGNEOUS ACTIVITY-materials injected into the crust are called intrusive landforms. These may later be exposed at the surface by erosion of the overlaying rocks.

Laccolith

This is when magma cools between layers; it is smaller than a batholith.

Example: Pine Valley Mountains, Utah, USA

• The laccolith is made of granite.
• Largest laccolith in the USA.
• Formed as a result of the formation of Grand Canyon.
• Location of endemic species, e.g. the zebra tailed lizard and the Uinta chipmunk.

Batholith

They are large masses of intrusive rock that forms a doming of the surface as they are forming. Heat is transferred from the magma causing metamorphic rock; it lacks linear valleys and ridges.

Example: Chilean coastal batholith

• Formed by the South American plume in the Jurassic Period approximately.

Sill

They are formed parallel to bedding planes; the cracks run horizontally and provide a line of weakness where the magma flows. As it cools, the magma contracts, providing cracks in the rocks.

Example: Whin Sill, UK

• The Whin Sill complex is usually divided into three components: Holy Island Sill, Alnwick Sill and the Hadrian’s Wall-Pennines Sill, which were created by separate magma flows but about the same time.
• Its thickness is approximately 70 metres.
• It lies partly in the North Pennines Area of Outstanding Natural Beauty and partly in Northumberland National Park.

Dyke

Cut across the bedding planes of the rock. Magma forms cracks and weaknesses, it cools and solidifies before reaching the surface and forms linear ridges when exposed.

Example: Mount Calanna, Mount Etna, Italy

There is evidence of a dyke swarm.

Effects of earthquakes on landscapes

Faults

Faults are breaks in the Earth and this is because of the cold temperature of the Earth, when it is stressed (probably through an earthquake), it tends to break. Faulting often occurs at the plate boundary but it also occurs in the middle of the plate- intra plate boundary. Faulting occurs if one or more plates slip and the exposed fault are referred to as a fault scarp.

Normal fault

• Hanging wall drops down.
• Forces are divergent (extensional).

Sierra Nevada Fault

It was located on the California-Nevada boundary. Surface rupturing earthquakes led to surface ruptures of 14 miles. This is known as a fault area because several faults have ruptured from the large fault. There are six faults in this area which are six foot in length each.

Glarus Fault, Switzerland

The Glarus Fault is a major fault in the Alps in Switzerland and is now a UNESCO world heritage site.

Reverse fault

• Hanging wall moves up.
• Forces are compressional.
• Common at convergent plate margins.

Cascadia fault

It is caused by the North American and Juan de Fuca plate. It is 800 miles in length, the lock zone is located off Oregon and there is a definite tsunami if the fault slips.

Strike-slip fault

• Walls move sideways.
• Fault planes are vertical and so there is no hanging or foot walls.

The example is the San Andreas Fault

• 700/800 miles in length

‘San Andreas lake’ (location of San Francisco’s water supply) is a valley; the result of the fault creates an impermeable layer of rock.

Segments of the San Andreas Fault:

1. Northern segment-ruptured in 1906-shelter coveàSan Francisco bay
2. Creeping (3cm a year movement)-San Juan BautistaàParkfield
3. Parkfield-centre of San Andreas fault
4. Central-uplifted mountain ranges-fault surges 40 degrees towards the North West.
5. Southern-small segment of crustal spreading. Thermal activity as a result of small volcanoes and geothermal power plants.

Rift valleys

RIFT-elongated basin that occurs by opposed faults.

East African rift valley

The rift valley affects Ethiopia, Kenya, Tanzania and Uganda.  It is a result of the old plate (Nubian) makes most of Africa, whereas, the new plate (Somalian) is diverging away. Volcanic mountains occur as a result, e.g. Mt Kilimanjaro and Nyragongo volcano. In a few million years, Eastern Africa will have split and this is because the plates form a triple junction. It is caused by flood basalts as lava erupts at fractures.

Dankalia-East African Rift Valley

The Dankalia depression (volcanic desert) is 120m below sea level. It is rifting as it is part of the East African Rift Valley. The Erta Ale volcano is located in the depression it is a permanent lava lake and this is one of five in the world. Fumaroles are examples of extrusive activity and this is created as rifting creates faults which allow water into the crust, heating and ejecting steam.

Nyragongo volcano

It is a very hazardous volcano because it is located on the eastern edge of the Democratic republic of Congo; the risk is to the city of Goma directly below it. The extrusive activity includes geysers. There is a large level of vulnerability because the city of Goma has a large population of one million and due to conflicts there is a large population. If this volcano was to erupt, there would be definite 1 million casualties as houses are created from lava rock. There are constant conflicts because there is constant warfare with neighbouring Rwanda and it is the location of one of the largest UN forces-20,000 troops.  The effects of the eruption could lead to a suffocating effect because Lake Kiwu has a large concentration of methane and CO₂.

Micro fracturing

• Small scale fractures.
• Releases stress under high pressure.
• Used to predict rock failures.

Analyse the stress that gives rise to faults

Cold brittle surface does form more cracks and lead to faults but the fault occurs due to the strength of the convection currents.

How are earthquakes formed?

They are formed by the elastic rebound theory.

Stress is applied to an existing fault over a period of time and as the stress builds, the locked fault deforms elastically. Eventually the stress overcomes and the friction occurs.

Orogeny

OROGENY-they are forces leading to structural deformation of the Earth.

OROGENESIS-this is where collisions crumble and thicken to form mountain ranges.

How do mountains form?

Mountains form through faulting, folding, volcanic activity, intrusion and metamorphism.

METAMORPHISM-this is altercation of the composition/structure of a rock.

Fold Mountains

They are not formed in areas of tectonic but adjacent areas. The frontal thrust spreads a large distance and further movement can give rise to folds. Most fold mountains are eroded.

The Alps

They are high mountain ranges and are 30-40 million years old and there was a collision of the Eurasian and the African plate, e.g. the Western belt.

Fold-thrust belt

Foothills are adjacent to an orogenic belt and formed due to compression.

Fault-block landforms

This includes mountains, ridges and hills. There are displacements of the crust made by fracturing; the vertical motion is accompanied by tilting.

Block Mountains

This occurs when stress is extensional and the crust is thinned.

Tectonic hazard human impacts

Why do people live in tectonically active areas?

• By 2025, 600 million people will be living in tectonically active areas-increase in disasters.

People live in tectonically active areas because of:

1. Choices: climate, jobs, inertia, lack of knowledge and lack of finance.
2. Benefits: natural resources, fertile soil, tourism and geothermal energy.

Choices

1. Climate- in locations where the climate is pleasant (hot summers/cool winters) usually mean that people can afford to prevent and prepare for tectonic hazards. In many cases, the benefits outweigh the costs.
2. Jobs-in areas of well-paid jobs, there is an ability to plan and prepare. Again, the benefits outweigh the costs.

Case study: California, USA

The benefits include the job prospects and this is mainly through Los Angeles and Hollywood. There is a diverse range of culture and there is a pleasant climate.

The costs include the fact that it is an earthquake prone area but the large majority are below magnitude, they are higher magnitude earthquakes but they can still prepare and repair. Californians live close to one of the most known faults in the world: San Andreas and there is also the possibility of the “big one” from the unzipping of the Cascadia fault.

Inertia

This is often related to traditional, historical or cultural reasons to living in a tectonically active area.

‘Living the hazard’ –this is when the population has been previously established and so have set values and don’t want to leave the community.

Lack of knowledge

Many people assume tectonic hazards only occur on plate boundaries; in fact tectonics can occur anywhere on the Earth’s surface.  There is often a lack of knowledge in places where the tectonic activity is limited or uneven.  In areas of low economic development, the resources and research to study the environment and identify areas of high risk. There is also the fact that it may not be a governmental priority, there are other factors that the government is concerned with.

Ignorance

This is often associated with limited tectonic knowledge because people are often unaware of the hazardous areas and this is often associated with areas of limited tectonic activity. However, it could also be associated with areas where the area to be destroyed is of high value, i.e. the person’s livelihood depends on this.

• Example is in the Philippines, in the Mount Mayon eruption (late 2009/early 2010), 3000 farmers refused to evacuate. Refer to the Philippines (tectonic activity and causes).

Education

High level of education is often associated with areas of high economic development, the ability to prepare residents through drills and information leaflets.

California, USA

The Earthquake Country Alliance prepares people for a tectonic hazard; examples of campaigns include the ‘drop, cover and hold on’ and the Great Shake Out drill that occurs every October.

Benefits

Natural resources

The establishment of mines are common in areas of volcanic activity and this is because ore deposits are created as a result of heat generated causing ore-bearing fluids to be circulated. Examples of this include copper, zinc, gold and lead.

• 500 million people live near a historically active volcano.

Mt Etna, Sicily, Italy

• Basaltic lava causes mineral rich soil and this is perfect for cultivating vine yards, citrus plantations and orchards.

It is Europe’s most active and tallest volcano, it is a composite/stratovolcano and is listed as a UNESCO world heritage site: supports endemic flora and fauna.

Features included in Mount Etna

1. Summit craters and calderas (Ellitico caldera).
2. Cinder cones.
3. Lava flows.
4. Valle de Bove depression.
5. Mt Calanna (evidence of a dyke swarm).

Geothermal energy

This is water running through the Earth’s crust which is heated and this brings geothermal energy to the surface where it emerges as hot springs and fumaroles.

Iceland

• 85% of all houses in Iceland are heated with geothermal energy.

Tourism

Modern cultures (especially the Western culture) find volcanoes beautiful as well as threatening. Volcanic regions bring tourism employment.

• According to the BBC, the 25 Icelandic volcanoes have long been the centre of Iceland’s tourism.

Disaster-loss-recovery cycle

This is a continual event because of the socio-economic factors. It becomes chronic as it becomes more difficult for the area to cope.

Human factors are likely to increase the chance of death, because of the lack of preparation, political stability and aid.

Haiti

Many of the factors that lead to the affected population or death are determined by more than one factor; this is demonstrated in Haiti’s 2010 earthquake.

Support (in terms of aid) was made available for Haiti by Qatar, Iceland, the Dominican Republic and America but political factors prevented people from being rescued/saved etc. ICE-SAR (the Icelandic search and rescue) team were 24 hours late because of the lack of support by the government and a hold up at the airport. Also, American supporters pledged money for the aid of people in Haiti; however, half of this was used as debt relief. In addition to this, American Red Cross ran out of supplies and this prevented from everyone being reached at the time when they needed to.

After the disaster, the follow up effects also represent the problems because of the political instability, in Haiti, housing is not prioritised by the government and so this led to the focus on NGOs to provide support. The political instability is a result from corruption and drug/people trafficking. Oxfam (in January 2012) found that ½ of people from Haiti still live in the tents provided two years ago. Not as a direct result from the disaster, there were secondary effects that include waterborne diseases, e.g. cholera. This became an epidemic in Haiti and increased the deaths, the time of response and the effects of recovery.

Haiti was not at the stage of recovery when it was hit by cholera and this is because 80% of people live below the poverty line and so cannot recover as quickly as areas of more economic developed. The area is challenged by the lack of resources and its incapability to recover from each disaster.

However, this fault was locked for two hundred years and so in terms of disaster it hasn’t always been tectonic, other disasters resulting from poverty have played an effect.

Philippines

The Philippines is referred to as a disaster hotspot and so the disaster-loss-recovery stage is much more prominent throughout the GDP development of the country and the life expectancy.

The graph is another from gap minder but this portrays the disaster-loss recovery, in the early 1900s, there was the first disaster, the country had faced since records had begun recording. The life expectancy was 34 in 1904 and the GDP was 740, it then dropped to 0. This is because of the first disaster and then there was a rapid recovery, at this time, it is most likely to have been from aid from other countries. The Philippines recovered and appeared stable for nine years (1909-1918) but then another disaster (not as catastrophic as the first) hit the Philippines. The life expectancy had dropped by five years (30 to 25) and GDP had dropped by 400. This is identification of the disaster-loss –recovery cycle. It is not continual, there are areas of development but there are also times of disaster.

The Philippines is affected by many disasters including tectonic (Pacific Ring of Fire) and so continuously is affected by disasters. However, as areas become more economically developed, they can become more prepared. This means that disasters that occurred in the 1900s that occur at the same magnitude/strength won’t have the same effect; it won’t drop the life expectancy to 0.

Trends of hazards

Frequency

There has been a general increase in the number of recorded earthquakes in the world. This is a result of the increase in the number of seismograph stations and increased global communications; this means that lower intensity earthquakes have been detected in the past. There has been an increase in the number of earthquakes between the number of earthquakes between 1997 and 2007-this may be a result of climate change (the isostatic rebound theory).

Impacts

There have been an increased number of fatalities because of the exponential growth of the population (7.2 billion). There may have been a possibility of decrease in the future because of the improvements in preparation and the implementation of frameworks, e.g. Hyogo.

Japan earthquake, 2011

• Defined as a mega disaster.
• The 4^th largest in the world.
• MAGNITUDE-9.0
• TIME-17:15
• LOCATION-Sendai, Japan
• PHYSICAL IMPACTS-Tsunami was spread across the whole eastern coast and the Pacific Ocean. The plates moved at least 10 metres.
• HUMAN IMPACTS-

Sendai

Fukushima Daiichi Nuclear plant went into a partial meltdown with a level 7 on the International Nuclear event scale (which was the same as Chernobyl). 400mSv released in an hour. Some food sources were contaminated, in September 2013; South Korea banned importation from the Sendai region. 3,900 roads were damaged.

Are there any global effects?

Radioactivity found in the waters of the USA. 23% of the population are elderly. There was a global reassessment on energy security and are they hazard proof?

Tectonic proof

The Japan Meteorological agency and they are a large volume of houses with resilient buildings.

EMERGENCY RESPONSE-there was a 20km exclusion zone with 70,000 migrated and 120,000 advised to stay away as a result of thyroid cancer.

 

Responses to tectonic hazards

Soufriere Hills, Montserrat, 1995à2010

There were five phases.

1 the steam was raised, the evacuation of the capital Plymouth and the dome of the volcano collapsed sending 5 million m³ of tephra. The pyroclastic flows killed 19 farmers and emigration of half of the population.

5 There were seismic activity, ash flow, pyroclastic flow and Vulcanian eruptions. There was an added 650m of land to the coastline and ash fall to other islands, e.g. St Lucia.

Predicting

• Seismic activity.
• Inflation of the magma chamber.

 

Park’s disaster response model

The relief phase included teams from the immediate area to arrive to help.

The rehabilitation phase included actions designed to restore physical and community structures. It requires an accurate reassessment of needs and coordinated planning of responses.

The reconstruction phase includes permanent changes are introduced to restore the quality of life and economic stability to its original level.

Strategies for coping

Earthquake risk assessment

• Human populations have expanded into earthquake risk zones- especially as buildings and infrastructure are becoming increasingly vulnerable and expensive.
• Areas where written records do not exist, geological and soil maps can be used to identify past earthquake activity.
• Areas of high risk include steep slopes, sensitive soil or low lying coastal areas.
• The location of mains services.
• Size/design of infrastructure will have an impact on potential damage and evacuation.
• Height of buildings.

Earthquake prediction

• P wave/S wave ratio drops prior to a large earthquake.
• Warning activity with small tremors.
• Water levels rise or falls as the rocks are squeezed by the strain of the pressure.
• Radon (radioactive gas) levels in well which is released from the rock pores as squeezed by the rock strain.
• Levels of manganese, zinc and copper in basaltic rocks at a depth of 1000m increased by over 10005.
• Change in the electric properties of rocks occurs as an increased strain causes a change in the rock.
• Ground deformation.
• Animal behaviour.

None are reliable!

Volcanic risk assessment

• Levels of activity.
• Mapping evidence of previous eruptions.

Modify

Planning for earthquakes

Damaging earthquake factors

• Occurs without warning.
• Pre-event response is not possible.
• Probability of event occurring during working hours.
• Damage to communications.
• Intense aftershocks.

 

Strategies to reduce impact

1. Land-use zoning.
2. Building regulations.
3. Evacuation drills.
4. Emergency services.

Iran, 2013

• MAGNITUDE-7.8
• TIME-10:$4
• LOCATION-East Iran
• PHYSICAL IMPACTS-Biggest earthquake in 50 years and the depth was 51km.
• HUMAN IMPACTS-Largest province of Sichuan Baluchistan shook buildings in India and Dubai, traffic came to a standstill and 40 were dead.
• EMERGENCY RESPONSE-Red Crescent sent 20 search and rescue teams, and 5 helicopters. The infrastructure was fixed in 30 minutes.

Evaluation

• The change to social, economic and environmental conditions.
• Associated events could take an effect, e.g. climate change.

Hyogo framework

The Hyogo framework provides a strategic and systematic approach to reduce vulnerabilities and risks. It identifies ways of building resilience of nations and communities.

The priority was to conclude on the Yohohoma strategy, share practices/lessons on further disaster reduction, increase awareness of policies and information.

The implementing ensures disaster risk reduction on a local and national level and use knowledge to build culture of safety and resilience.

Disaster preparation

Indian Ocean tsunami, 2004

• Approximately 220,000 killed.
• 58,555-the number of people are affected.
• 120,000 + lives were affected as a result of tourism.

Indonesian earthquake, 2012

• People moved to a higher ground.
• At least 8 countries issued tsunami alerts after the 8.6 earthquake.
• Countries such as Sri Lanka and Thailand have heavily invested in disaster response.
• Phones alerted people to the risk.

Drabek and Hoetmer’s four stages of emergency management.

1. Mitigation- avoiding and reducing the risk.
2. Preparation-lessen the effects.
3. Response- reduces the impacts.
4. Recovery-return to normality.