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50 Cards in this Set

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Why are some landforms found at different plate boundaries and how are they formed?

Causes: Movement of plates at different plate boundary

Different formations: fold mountains, rift valleys, block mountains and volcanoes.

Causes: movement of ???

Different formations : FM, RV, BM and V

Fold Mountains

Formed along convergent plate boundaries, where the plates collide.

Compressional force creates immense pressure which cause the layers of rocks to buckle and fold.

Process called folding.

Upfold = anticline

downfold = syncline

Increasing compression force on 1 limb of the fold --->fracture form

limb may then move forward to ride over the other limb

e.g.Himalayas (formed from indian plate with Eurasian plate)

Plate movement

CF creates immense p_______

which cause ???

process called F ______

upfold = ???

downfold = ???

Increasing CF on 1 limb of the fold forms FF

limbs may ???

Rift valleys

Formed along divergent plate boundaries, where the plates are pulled apart

Tensional forces causes parts of the crust being fractured.

Process called faulting

Rift valley = valley with steep sides.

Formed when sections of the crust extend along fault lines.

Central block of land subsides between two parallel faults due to tensional forces.

E.g. East African rift valley formed due to divergent Somalian and Nubian boundary of African plate

Hutt Valley (divergence of Australian and Pacific plate)

Plate movement

TF cause ???

Process called F _______

Rift valley = valley with ??? sides

formed when section of crust ???

central block of land s_____ between two parallel f____

due to TF.

Block mountains

Block mountains = block of land with steep sides.

Formed when sections of the crust extend along fault lines.

rock masses surrounding a central block sink due to tensional force.

The land left standing higher than the rest is a block mountain

E.g. Vosges in France and Black forest in germany seperated by the Rhine valley. (divergence of Eurasian and North American plate)

Block mountains = ???

Formed when section of the crust ???

Rock masses surrounding ???

s_ _ _ due to TF

block mountain is ???


1) Magma from magma chamber rises to the surface through the vent.

Lava = magma ejected->earth's surfact

2)Lava builds up around the vent, solidifying---> form a small volcanic cone.

Crater = bowl-shaped opening

3)volcano erupts, lava, ash and rock fragments are released. Force of volcanic eruption = amount of pressure and gas in the magma

4) The summit of a volcano may be blown off during an explosive eruption.

The sides of the crater collapse inwards due to the loss of structural support.

a caldera (large depression) is formed

e.g. caldera of mount bromo in Java

5)New eruption of lava covers the ash layer and builds up the volcano

6) during the formation of the new volcano, the vent may become blocked. The magma finds a new exit route to the surface. A secondary cone of newer volcanic material will then develop.

1) Magma goes up and out


3)releases stuff

4) Explosive diarrhea causes sides to collapse due to lack of structure. C _ _ _ _ _ _

5) New eruption ---> new volcano

6)eruption blocked the route of magma. Magma find new way

S cone developed.

Meaning of Magma, vents, vulcanicity

Magma meaning: molten rocks beneath earth's surface and builds up within the crust to form magma chamber

Vents meaning: openings in the earth's in earth's surface with a pipe leading into the magma chamber.

vulcanicity meaning: The upward movement of the magma both into the earth's crust and onto the earth's surface

Ur on ur own.

Shapes and sizes of volcanoes

Depends on the characteristic of lava. Low-silica lava = low viscosity, High-silica lava = high viscosity.

Viscosity = stickiness of the lava or its resistance to flow.

Low = Low

High = High

V________ = characteristic of lava

Low-Silica lava

Lower viscosity = less explosive volcanic eruptions.

This type of lava allows gases to escape easily and flows more easily through the vent before reaching the surface

On earth's surface, outer layer of cooling lava forms a thin crust

Less/more explosive

Gases/ Flows ---> vent

outer layer---> ???

High-silica lava

More viscous = traps gases more easily = build up more pressure below the earth's surface. As magma rises ---> gases expand ---> outward explosion.

volcanic eruption ejects lava, ash, rock fragments and gases into the surrounding environment.

More/less viscosity = _____ gases more easily = build up more _________ below the earth's surface. Magma rises---> ???? ---> ???

Volcanic eruption ejects 4 stuff

Types of volcanoes

Strato volcanoes and shield volcanoes

Strategy and shields

Shield volcanoes

Gently sloping sides and a broad summit.

Formed when low-silicia lava is ejected.

Low-silicia--> flows easily--> spreads out over large areas before solidifying.

Lava---> gas escapes easily ---> not explosive usually.

successful eruption---> base of the volcano increases in size

Shield volcanoes are common near divergent plate boundaries where magma can rise directly from mantle

E.g. Mount Washington in USA

Steepness of slope

Lava characteristic

Successful eruption --> ???

Most common in ???

E.g. ??

Strato volcanoes and shield volcanoes

Develops from successive eruption of lava and ash.

Ash deposits can also contain coarser rock fragments from the vents

After an initial eruption, the subsequent eruption--> eject lava --->cover soft ash--> prevent it from being eroded.

Overtime, successive eruption---> builds a high volcano with a slightly concave profile.

Meaning: steeper top, gentler bases

Develops from ???

Ash deposits contains ???

After an initial eruption, the subsequent eruption --->???

Meaning of conclave profile

Pryoclastic flow meaning

Results from volcanic eruption.

Pyroclast: Hot rock fragments and super heated gases ejected during a volcanic eruption.

The movement of rock fragments and gases down the slopes of an erupting volcano = pyroclastic flow.

pyroclast= Hrf and shg ejected during a volcanic eruption

Pyroclastic flow = the movement of ???

Lahars meaning

Results from volcanic eruption.

Lahars: Mixture of pyroclast and melted ice from mountains.

Wet volcanic debris flowing down the slopes o an erupting volcano

Pryoclastic flow of an icy volcano

Distribution of volcanoes

The pacific Ring of fire is where the most active volcanic activity occurs.

Mostly along the edges of the pacific ocean where the pacific ring of fire is located.

The pacific ring of fire is found along the boundaries of several converging plates.

Like Pacific plate, Nazca plate, the Philippine plate, Australian Plate and the Eurasian plate

What is the pacific ring of fire

Where is it found? P, N, P, Au, Eu

What phenomena are found at plate boundaries and how are they formed?

Earthquake, Tsunamis, volcanic eruption

3 type of phenomena

Definition of an earthquake.

Occurrence of an earthquake

vibration in earth's crust caused by the sudden release of stored energy in the rocks found along the fault lines.

Occurrence: Plate movement along plate boundaries.

The plate movements--->slow build-up of stress on the rocks.

Rocks can't withstand the pressure---> suddenly slip many metres --> earthquake.

V_________ in earth's crust caused by ???

Occurrence : plate movements --> ???

How earthquake occur?

Earthquake releases energy in forms of seismic waves.

Seismic waves radiate out from a point of sudden energy release, called the focus.

epicentre: directly above the focus, on the earth's surface

Most of the energy released by an earthquake travels to earth's surface to vibrate violently

Earthquake releases energy in forms of ???

??? radiate from a point of sudden energy called ???

meaning of epicentre:

Location of focus

Deep-focus earthquake:

Occurs between 70~700km below earth's surface

Shallow-focus earthquake:

Occurs in the upper 70km of the earthquake

70km on 2 type of earthquake

Impact on land

Deep-focus earthquake:

smaller impact on the land as vibration or seismic waves take a longer time to reach the surface and would have lost most of their energy by then

Shallow-focus earthquake:

Greater impact on the land as vibrations or seismic waves reach the land surface more quickly

How fast the vibration reach the earth----> smaller/greater impact

Meaning of aftershock

aftershock = smaller earthquakes may occur after an earthquake along the fault line

A series of aftershocks may occur for several months after the initial one, some being as powerful

Initial earthquake's aftermath

Magnitude of an earthquake

Measurement tool: Richter scale.

each increasing magnitude---> the impact of the earthquake becomes 10 times greater in magnitude than the previous one.

Measuring tool: ???

each increasing magnitude --> ???

Magnitude on the Richter scale vs impact on land

1.0-2.0 :

usually not felt by people but detected by seismograph. often referred as tremor


felt by few people near the epicentre; referred as a tremor


little damage to structures; hanging objects swing


minor damage including cracks in walls;felt by many people ; stationary cars and rock


shock can be damaging to poorly constructed buildings: furniture moves; walking is difficult


Many structure collapse; cracks appear in the ground; difficult to stand during the earthquake


severe damage, most buildings collapse


destruction over a wide area; landslides can be common

more than 9.0:

destruction can impact thousands of kilometres of land.

Ur on ur own

what factors affects the damage/casualties caused by the earthquake?

Population density

level of preparedness

distance from the epicentre

Time of occurrence

Type of soil

Population density

Earthquakes in sparsely populated areas are likely to affect fewer people than in densely populated areas.

Therefore, an earthquake in a city can cause more casualties and damage than an earthquake in the countryside

Level of preparedness

The preparations include having evacuation plans, trained rescue workers and a range of action plans.

The damage caused by an earthquake is more manageable when people are better prepared for it .

Time of occurrence

If the earthquake occurs when most people are sleeping, there is a higher chance that these people will be trapped in their houses and more deaths may occur.

E.g. More than 2.400 people died when an earthquake occurred a couple of hours after midnight in the Sun Moon Lake Region in Taiwan in 1999

Type of soil

In places where the sediments are loose and unconsolidated, the seismic waves are amplified and this results in greater damage when earthquakes occur.

Structures build on saturated and unconsolidated sediments can be affected by liquefaction.

*liquefaction = when the ground becomes unstable and saturated soil flow like liquid. In christchurch, many houses and buildings had to be abandoned because of liquefaction after the earthquake in 2011

Locations of earthquakes

earthquakes occur most frequently at convergent plate boundaries.

Stress builds up when a plate subducts beneath another

E.g. Devastating earthquake in Tohoku, Japan, in 2011 and the earthquake in Indian Ocean in 2004

Measuring earthquake

Measurement tool: Seismograph

Records the seismic wave released by an earthquake.

A spring-weight in the seismograph moves up and down when tremors are detected. An ink marker then records the motion of the ground by making vertical markings on a piece of graph paper which is attached to a rotating drum *not important*

Hazards associated with living in earthquake zones

Threat of tsunamis,disruption of services, fire, landslides, destruction of properties, destruction of infrastructure and loss of lives

Threat of tsunamis

Tsunamis: A large sea wave

Caused by:

1)The movement of sea floor during a large earthquake at the subduction zones

2)An explosive underwater volcanic eruption

3)an underwater landslide

4)A landslide above sea level which cause materials to plunge into the water. Such landslides may be due to earthquakes or volcanic eruptions

How a tsunami is formed?

Formation of tsunami wave starts when seismic energy from an offshore earthquake forces a mass of sea water

The tsunami waves may start at a height of less than 1m, with wave lengths of 100 to 150 km, at speeds of 800km/h and may pass undetected

On reaching shallower water, greater friction slows the waves and forces them to increase in height

At the point of impact on the coast, the tsunami waves could be travelling at 30 to 50km/h and may reach height of around 15m

Seas recedes from the coast before advancing onshore. It only takes minutes after receding before the tsunami reaches the shore. The sea recedes as water rushes to fill the void caused by the movement of the sea floor . Water is then forced out again soon afterwards, resulting in a tsunami.

Damages by tsunami

Tsunamis can travel long distances and cause widespread destruction at coastal areas when it sweeps inland

E.g. 2004, a 9.2 magnitude earthquake occurred in the Indian Ocean and triggered a tsunami with waves that spread throughout the Indian ocean.

Disruption of services

An earthquake can disrupt services such as the supply of electricity, gas and water and potentially affect a large area.

Communication service such as television broadcasts and telephone connections may also be affected.

The earthquake in kobe , japan, in 2004 damaged pipe and transmission line. This disrupted electricity, gas and water supplies to about a million of kobe city's 1.4 million resident


Earthquake may rupture gas pipes and the gas can provide fuel to start fires. Earthquakes can also expose electrical cable to ignite flammable items such as gas, oil, chemicals and plastics.

Fires have ability to spread quickly over a large area, increasing the number of fatalities.

The earthquake in Kobe, Japan, in 1995 caused extensive fires that raged on and off for two days. Hundred of fires were ignited by toppled gas cookers and kerosene stoves as households were preparing their morning meal.

Ruptured water pipes meant that no there was no water supply to control the fire.


The shaking of the ground during an earthquake can weaken the slopes of hills and mountains. The unstable slopes may result in landslides.

Landslides : rapid down slope movements of soil, rock and vegetation debris from a slope. They can range from several metres to several kilometres in both length and width

E.g. 1970, an earthquake off the coast of Peru destabilised the slopes of mount Huascaran and triggered a massive landslide. The death toll was more than 18,000 and only 200 people survived from the disaster.

Destruction of properties

Earthquake can cause widespread destruction to many homes. People may be without homes after the disaster and reside at temporary shelters while their home are being rebuilt.

e.g. The earthquake in Tohoku, japan, in 2011 caused a tsunami which travelled up to 10 kilometres inland. Extensive structural damage resulted in hundreds of thousands of people becoming homeless There was a severe shortage of housing and concerns about the long-term consequence on the health of the people.

Destruction of infrastructure

Earthquakes may cause cracks to form in infrastructure such as roads and bridges.

Transportation can be disrupted as it is unsafe to use the damaged roads.

E.g.after the earthquake in Kobe, Japan, in 1995, many places in the city become inaccessible or difficult to reach.

Loss of lives

Earthquake and their associated hazards often threaten the lives of those living in earth zones.

meaning of Active, dormant and extinct volcanoes

Active volcanoes : volcanoes which are currently erupting or are expected to erupt in the near future

Dormant volcanoes : currently inactive but may erupt in the near future

Extinct volcanoes : without current seismic activity and with no geological evidence of eruption for the past thousand years

Risk of living near volcanic areas

Destruction by volcanic materials



Effects on weather

Destruction by volcanic materials

Volcanic materials: lava and rock fragment or volcanic bombs.

They can lead to widespread damage of properties as the lava flows at high temperature of 500~1,400*C burning the area it flows.

Low-silica lava moves rapidly and flows over long distances, causing damage to larger areas. A pyroclastic flow can destroy everything in its path with hot rock fragment ranging from ash to boulder travelling at speed greater than 80km/h. Inhaling the hot ash and gases can result in serious injury or death.


Landslide occur due to structural collapse of a volcanic cone during a volcanic eruption.

The landslide can range from a few rock fragments falling from the volcano to landslides ranging to a few km^3.

It also have the potential to obstruct the flow of rivers causing floods, blocked roads and buried villages and farmlands

E.g. The eruption of nevado del rulz in the Andes mountains of south America in 1985 released a pyroclastic flow mixed with glacial ice creating lahar. lahar which engulfed the town of Armero and killed more than 20,000 people


Thick plumes of ash may settle on the ground, blocking sunlight, suffocating corps, and cause severe respiratory problems for people

It releases gases such as carbon dioxide, sulphur dioxide, hydrogen and carbon monoxide which may be harmful to humans

e.g. Eyjafjallajokull in Iceland in 2010 produced extensive volcanic ash clouds containing tiny particles of glass,sand and rocks which pose a threat to aircraft engines.

Benefits of living near volcanic areas

1)Fertile volcanic soil

2)Precious stones and minerals ; building materials


4)Geothermal energy

Fertile voanic soil

As the richest soils on the earth, volcanic soils are very favourable to agriculture. Although they are rich in minerals, the minerals are not available to plants when the rocks are newly formed.

They have to be broken down throughout thousands of years before they can be used

E.g. The volcanic soil Java and Bali in Indonesia support the cultivation of crops such as tea, coffee and rice. That's also the main reason why can they support a large rural population over decades and have more fertile soil than most non-volcanic areas of Indonesia.

Precious stones and minerals, building materials

Volcanic rocks can be rich in precious stone and minerals. These resources can only be extracted from volcanic areas after million of years.

When the upper layers of volcanic rocks are eroded, the precious stones and minerals can be extracted

E.g. Diamonds, they are heated and pressurised carbon that cooled in magma pipes beneath the earth's surface.

When refined, diamonds are useful as industrial tools and in scientific research. They are also used to make jewellery.

Kimberly in South Africa are one of the world's richest sources of diamond.


Volcanic areas offer a large variety of activities for tourism to be engage in. Many people visit volcanoes to hike and camp in area or simply to enjoy the scenery. It is also rich in history.

E.g. Ruins of Pompeii, Italy was buried by layers of ash from the nearby mount vesuvius when it erupted in 79 CE.

Geothermal energy

When groundwater comes into contact with hot rocks beneath the surface, it heats up and erupts as hot water or steam.

The hot water or steam can be harnessed to drive turbines and produce electricity.

E.g. Most of Iceland's electricity is generated from geothermal power because of the large number of volcanoes in the country. Over 70% of homes in Iceland are heated by volcanic steams