Millions of years ago there was one large continental land mass called Pangaea. As the plates drifted apart this split into two. The northerly one was called Laurasia and the southern one Gondwanaland. The plates moved through the power of the convection currents operating in the upper mantle. Today the plates have formed a pattern which was very different to the past. For example the white cliffs of
Dover were formed in tropical seas, as at one time Dover was in the tropics!

Continental Drift > Alfred Wegner’s theory
Evidence:
•Jigsaw Theory – Brazil’s east coast fits into western
Africa- this was because at one time they were part of the same supercontinent – Gondwanaland
•Fossil evidence – the same fossils have been found in Antarctica and South Africa – because they were once connected
•White cliffs of Dover – are made of chalk which was laid down in a tropical sea – so at one time the
UK was once in the tropics!
•Alternating magnetic bandings in the North Atlantic

P10 Q2C/D Summary
As the strength of an earthquake increases so does the risk of death
There are exceptions however:
LEDC’s are less able to cope with earthquakes - the buildings are often made of poorly constructed materials (eg Turkey)
MEDC’s are better able to cope with earthquakes they have the money to invest in making sure that the buildings are strong (eg San Fransisco, USA)
Mankind is getting better at predicting and preparing for earthquakes - which explains why so many people died in the Japan quake of 1923 (156,000)

•People are made homeless - refugees
•Bridges collapse
•Looting of buildings after the earrthquake
•Millions of £ of damage is caused
•Insurance companies struggle to pay the costs of rebuilding
•People trapped in buildings and cars
•People die
•Fires start - eg Kobe Earthquake 1995
•Burst gas and water pipes
•Electricity wires are damaged - therefore no power

•Strange animal behaviour - eg dogs, Japanese
Cat Fish, cows
•Monitoring stations - Richter Scale eg Parkfield,
California
•Scientists place monitoring equipment in the ground - eg Seismometers
•Richter Scale results
•Record previous earthquakes - see if there is a pattern

•(I) Constructive Ocean+Ocean Plate eg Mid Atlantic Ridge
(North American + Eurasian Plate)

•(II) Continental+Continental Plate
Eg East African Rift Valley
(African and Indian Plate)

•(I) Ocean+Continental Plates - eg Peru, Andes
(eg Nazca and South American Plates)

•(ii)Ocean + Ocean Plates Eg. Marianus Trench
(Pacific and Philippine Plates)

•(iii) Continental+Continental
Eg Himalayas, Nepal
(Indian+Eurasian Plates)

3. Transform Boundaries

Eg. The San Andreas Fault, California, USA

Off-set Highway on the San Andreas Fault

17th October 1989
7.1 Richter Scale
Causes:
San Andreas Fault - Transform Boundary
Building in Marina District - this was poor quality land - unsuitable for houses

Effects
•US$6Bn damage
•Fires
•62 died
•Gas mains broken
•Homeless people / Refugees
•Motorways / Roads collapsing

Protection
•Reinforced steel
•Deep foundations

Why do people live there?
•Warm climate
•Good standard of living
•Lots of jobs available
•People think it wont happen to them

The seismic gap theory
The part of an active fault that has experienced little or no seismic activity for a long period, indicating the build up of stresses that are useful in predicting earthquakes
1969-1989
3 weeks after 1989

Liquefaction
Japan 1963

Golden Gate
Bridge

Port and wharf facilities are often located in areas susceptible to liquefaction, and many have been damaged by liquefaction in past earthquakes.
Most ports and wharves have major retaining structures, or quay walls, to allow large ships to moor adjacent to flat cargo handling areas. When the soil behind and/or beneath such a wall liquefies, the pressure it exerts on the wall can increase greatly - enough to cause the wall to slide and/or tilt toward the water. Liquefaction caused major damage to port facilities in Kobe, Japan in the 1995 Hyogo-ken Nanbu earthquake .

Note the subsidence in the port in Kobe due to liquefaction

Are generally found at plate margins
Where 2 plates collide, the denser, heavier
Oceanic Plate “SUBDUCTS”, or sinks below the lighter Continental Plate
As it does so the ocean plate melts due to the build up of friction, heat and pressure
This forms molten rock or MAGMA
This Magma then rises to form a MAGMA
CHAMBER which builds up until it erupts

Volcanoes Video 114
Causes:
•Where 2 plates collide - (one oceanic and one continental), the denser oceanic plate sinks, or
SUBDUCTS, below the lighter continental plate.
•As it does so, the friction, heat and pressure builds up to such an extent that the plate melts into molten rock
•This molten rock is bouyant (lighter) and rises upwards to form a magma chamber
•Over time, the pressure in the magma increases and eventually is released in a volcanic eruption
•Eg Mount St Helens, USA - Juan de Fuca and North
American Plates 18th May 1980

Volcanoes - Effects continued:
•Volcanoes are also found at Constructive Plate
Boundaries - eg Mid Atlantic Ridge - where 2 plates are moving apart - magma rises to fill the gap - it cools and solidifies to form islands - eg Iceland
•As the magma rises it mixes with gases and travels along lines of weakness under the ground. These gases can cause the volcanoes to be very explosive when they erupt
•How explosive an eruption is depends upon how runny or sticky (viscous) the magma is. If magma is thin and runny it escapes easily and flows easily out of a volcano - eg a
CALDERA.
•If there is a high gas content in the magma the eruption can be explosive = SHIELD VOLCANOES - EG Mount
St. Helens, USA

Volcanoes: EFFECTS
•People die
•homes destroyed
•crops destroyed - fertile soils near volcanoes so many farms are near volcanoes
•roads destroyed
•contamination of water supply
•deforestation - I.e. trees uprooted and burnt
•animals die - damage to local ecosystem
•pyroclastic flows - hot clouds of burning ash and rock
•tephra - clouds of ash
•lava bombs - eg Mount Etna
•ash clouds - can travel hundreds of miles
•nuee ardente - powerful cloud of hot gas

•Earthquake activity - Richter Scale - eg Mount
Pinatubo in Phillippines, 1991
•Mountain may bulge as magma moves underneath
- eg Mount St. Helens (18th May 1980)
•Satellites
•Gas measurements at the crater increase
•Small pyroclastic flows
•Small eruptions of tehphra (ash) - eg Mount
Pinatubo 1991
•Is the volcano: active, dormant or extinct?

•Good access to escape - roads etc
•Emergency shelters - water, food, thick concrete walls
•Build huge walls to channel the lava or pyroclastic flows - eg Japan
•Annual “Disaster day” evacuation drills - where local people practice what they would do in the event of a volcanic eruption - eg Sakurijima, Japan
•Listen to the warnings and evacuate - eg Mount
St. Helens
•Don’t live near a volcano!

Volcanoes - So why do people live near volcanoes?
•The ground is fertile and very good for growing crops
- eg Japan
•Fishing - eg Heimay, Iceland
•They cannot afford to move away - cheaper housing may be there - and so they have no choice
•lack of awareness - eg CO2 emissions, Cameroon
•densely populated area - eg Japan - so no where else to live - eg Sakurijima Island
•Tourism provides money for local people - eg New
Zealand, Rotorou or Mount Etna in Europe (Italy),
Hawaii
•Religion - Bali - volcano represents a local god which they worship up the mountain
•Gold mining - Papua New Guinea

Why do people live near volcanoes:
Location 1 > BALI:
•The volcano is seen as sacred - the Balinese faith says that gods live up the mountain - and they have built a temple on the bottom slopes of the volcano
•The rocks near the mountain are useful raw materials for building roads and for carving objects which can be sold
•The soil near the volcano is fertile - rice is cultivated here very well - so people are reluctant to leave - as the volcano is seen as providing for their needs
•It also adds to the cultural richness of the area

Why do people live near volcanoes:
Location 2 > PAPUA NEW GUINEA:
•Large gold reserves and there has been a
“gold rush”
•There are very rich veins of gold here at
Wurou Wurou (30 grams per ton - which is a lot)
•Some people have made $25,000 per week gold-mining near the volcano

Why do people live near volcanoes:
Location 3 > New Zealand:
•Geothermal Industry near the volcanoes - which means that hot “bores” of steam (geysers) come up from the ground and this can be harnessed for energy in power stations - eg Wairaki Power
Station, Rotorua
•In total 8% of New Zealand’s power comes from such schemes - even hospitals use geothermal schemes
•Tourism - people come to bathe in the thermal hot pools
•Local people still cook using the thermal pools as the heat source - eg Mauri

Why do people live near volcanoes:
Location 4 > Hawaii
•Tourism - to see Mount Kilauea - where lava flows gently out of the volcano so can be viewed from a safe distance
•Also a good climate for tourists to visit
•The indigenous people to Hawaii believed that the volcano was sacred and so feared the gods up the mountain and were scared to leave
•More general points:
•People feel safe with modern prediction methods - eg satellites
•People take the view - that it will not happen to them, not in their lifetime
•People have lived there all their lives - so why leave eg Mr
Trueman at Mount St. Helens!
•The time between volcanoes is long - at least one generation so people easily forget when the last one was

Hot spots
Plumes of hot mantle rising to the surface

Hot Spots > a small area of the earth’s crust where an unusually high heat flow is associated with volcanic activity

Mount St Helens
Causes:
•DESTRUCTIVE PLATE BOUNDARY
•Magma rises up under the mountain - in Washington State
•Small earthquake triggered the landslide
Effects:
•Trees felled (flattened) 30km away from the mountain
•Mudflows
•Landslides
•Bridges collapsed
•Houses demolished - eg Mr Truman!
•Hot cloud of ash and gas emitted
•Glacier melted on top!
•Top 400m of mountain disappeared!
•31 people died in total

Effects cont.
•animals died
•pyroclastic flows
•people evacuated - escaped!
•State of Emergency Declared in Washington State
• Prediction:
•Look to history
•Small pre-eruptions
•Pig behaviour!
•Gas measurements - implies lava is on the move
•small earth tremors
•mountain bulges

Alaska earthquake of 1964

Prince William Sound, Alaska 1964 03:36:14 UTC,
9.2 on the richter scale
This great earthquake and ensuing tsunami took 125 lives (tsunami 110, earthquake 15), and caused about $311 million in property loss.
Earthquake effects were heavy in many towns, including Anchorage, in the downtown business section, at Government Hill, and at
Anchorage, about 120 km Northwest of the epicentre, sustained the most
Turnagain Heights . The largest and most devastating landslide severe damage to property. About 30 blocks of dwellings and commercial occurred at Turnagain Heights. An area of about 130 acres was buildings were damaged or destroyed in the downtown area. The J.C. devasted by displacements that broke the ground into many deranged
Penny Company building was damaged beyond repair; the Four Seasons blocks that were collapsed and tilted at all angles. This slide destroyed apartment building, a new six-story structure, collapsed; and many other about 75 private houses . Water mains and gas, sewer, telephone, multi-storey buildings were damaged heavily. The schools in Anchorage and electrical systems were disrupted throughout the area. were almost devastated. The Government Hill Grade School, sitting astride a huge landslide, was almost a total loss. Anchorage High School and
Denali Grade School were damaged severely. Duration of the shock was estimated at 3 minutes.

The earthquake was accompanied by vertical displacement over an area of about 520,00 square km. The major area of uplift trended Northeast from southern Kodiak Island to Prince
William Sound and trended east-west to the east of the sound.
Vertical displacements ranged from about 11.5m
of uplift to
2.3m
of subsidence relative to sea level. Off the Southwest end of Montague Island, there was absolute vertical displacement of about 13 - 15m .
This shock generated a tsunami that devastated many towns along the Gulf of Alaska, and left serious damage at Alberni and
Port Alberni, Canada, along the West Coast of the United States
(15 killed), and in Hawaii. The maximum wave height recorded was 67m at Valdez Inlet. It was also recorded on tide gages in
Cuba and Puerto Rico.

Close-up of Government Hill elementary school, which was destroyed by the Government Hill landslide. Anchorage, Alaska.

The waterfront at Seward a few months after the earthquake, looking north. Note the "scalloped" shoreline left by the underwater landslides that severed tracks in the railroad yard which dangle over the landslide scarp and the windrow-like heaps of railroad cars and other debris thrown up by the tsunami waves.
Alaska.

Uplifted sea floor at Cape Cleare,
Montague Island, Prince William
Sound, in the area of greatest recorded tectonic uplift on land (33 feet).

Tsunami damage on Kodiak island in Alaska

One span of the "Million Dollar" truss-bridge of the former Copper River and Northwestern Railroad was dropped into the Copper River by the earthquake, and the other truss spans were shifted on their piers.

Close-up of damaged homes at Turnagain
Heights landslide, Anchorage.

The Turnagain Heights landslide in Anchorage. Its length was about 1.5 miles; its width was about .25 to
.50 miles.
This landslide reduced to rubble many of the finer homes of the city. Failure here, and in the "L" Street,
Fourth Avenue, and Government Hill landslides in
Anchorage occurred on horizontal or near horizontal slip surfaces in the Bootlegger Cove Clay, a marine silt.

A subsidence trough (or graben) formed at the head of the
"L" Street landslide in Anchorage during the earthquake. The slide block, which is virtually unbroken ground to the left of the graben, moved to the left. The subsidence trough sank 7 to 10 feet in response to 11 feet of horizontal movement of the slide block. A number of houses seen in this photograph were undercut or tilted by subsidence of the graben. Note also the collapsed Four Seasons apartment building and the undamaged three story reinforced concrete frame building beside it, which are on the stable block beyond the graben.
.

This truck at Lowell Point, 2 miles from Seward, was bent around a tree by the surge waves generated by the underwater landslides along the Seward waterfront. The truck was about 32 feet above water level at the time of the earthquake.

A detail illustrating the violence of the surge waves that struck
Whittier: man holds mounted tire where wave has driven a piece of wood through the tire

.
The rails in this approach to a railroad bridge near the head of
Turnagain Arm were torn from their ties and buckled laterally by channelward movement of the river banks during the earthquake

Trees up to 24 inches in diameter and between 88 and 101 feet above sea level were broken and splintered by the surge wave generated by an underwater landslide in Port Valdez, Prince
William Sound.

KOBE

On Tuesday, January 17, at 5:46 a.m. local time, an earthquake of magnitude
7.2 (Mj) 1 struck the region of Kobe and Osaka in south-central Japan. This region is Japan’s second-most populated and industrialized area, after Tokyo, with a total population of about 10 million. The shock occurred at a shallow depth on a fault running from Awaji Island through the city of Kobe, which in itself has a population of about 1.5 million. Strong ground shaking lasted for about 20 seconds and caused severe damage over a large area.
Nearly 5,500 deaths have been confirmed, with the number of injured people reaching about 35,000. Nearly 180,000 buildings were badly damaged or destroyed, and officials estimate that more than 300,000 people were homeless on the night of the earthquake.
The life loss caused by the earthquake was the worst in Japan since the 1923
Great Kanto Earthquake, when about 140,000 people were killed, mostly by the post-earthquake conflagration. The economic loss from the 1995 earthquake may be the largest ever caused by a natural disaster in modern times. The direct damage caused by the shaking is estimated at over ¥13 trillion (about U.S.$147 billion). This does not include indirect economic effects from loss of life, business interruption, and loss of production.

One of the key factors in loss of life and damage to buildings in the Kobe earthquake was the extend of the fires that resulted.
The risks are particularly high in Japan because of
•high population densities;
•very narrow streets and alleys, which cannot act as fire breaks;
•numerous old wood-frame smaller commercial and residential buildings mixed in the commercial zones of towns;
•unanchored or unprotected gas storage tanks or heaters;
• and a mix of collapse-prone old buildings in all built-up areas

Nagata ward at
4.30pm on Jan
17th.

air). Some residents formed bucket brigades (with sewer water) to try to control the flames.

.
A typical street scene in a residential and light commercial area of Kobe. A house has collapsed, blocking the very narrow street and preventing access to the area by the fire department.
Thousands of narrow streets were blocked like this.
In other areas, many of the collapses were traditional buildings with ground-floor stores or shops and second-floor residential units.

Aftershock Maps from Kandilli Observatory and
Research Institute

This picture is on the far east end of the rupture. The fault went directly through the school - the chalkboard read something like:
"We're all happy because school is out".

This is where 6 large apartments buildings all were completely flattened. Luckily they were uninhabitated. Residents were supposed to have moved in during June, but were delayed. The fault is seen in the foreground. Aykut Barka has a photo taken of this area from a helicopter.