Geography Notes for EYAPlate TectonicsStructure of the Earth

Core ● Iron and Nickel:● SOLID in inner core● LIQUID in outer core

Mantle ● Mixture of magma (molten rock) and solid rock

Crust ● Oceanic (magnesium) (which is denser than continental)● Continental (aluminium)

Tectonic Plates● Major plates: African, Eurasian, North-American, South-American, Indo-Aussie, Pacific● Movement due to Convection Currents:

● High temps in mantle heat up magma● Magma rises● Magma spreads out beneath Earth’s surface -> divergent plate movement● Magma cools and sinks -> convergent plate movement● Magma gets heat up by mantle again

Types of Plate Movement

Divergent O-O

● Sea floor spreading: Fractures appear at boundary. Magma rises to fill gap, cools and solidifies to create new sea floors--->

● Resulting feature: Mid-oceanic ridge: new crust formed

Convergent O-O

● Denser oceanic crust subducts under less dense crust. One oceanic plate is denser because of age of sea floor. Further oceanic plate is located from the centre of sea floor spreading, the denser it will be.

● Landforms:○ Oceanic Trench (the depression in between)○ Submarine Volcanos (magma from melting of subducted plate. under intense pressure, rising through fractures in oceanic crust)○ Volcanic Island (submarine volcanoes build up above sea)

O-C

Oceanic-Continental● Oceanic plate subducts

under continental plate as it is denser

● Landforms:○ Oceanic trench (the depression in between)○ Volcano (caused by resultant magma from melting of

subducted plate under intense heat and pressure)○ Fold mountain (rock layers are compressed, causing rock strata buckle and fold)** Note: Since fold mountains take 1000s of years to form, volcanoes are formed first

C-C

Continental-Continental● Both plates are of same

density and buoyant so no subduction

● Fold mountain range (Collision of plates-->rock layers are compressed causing rock strata to buckle up and fold)

Detailed ExplanationsO-O divergent

1. Describe the kind of movement & Identify the plates: “Divergent plate movement of oceanic plates ---N. American and Eurasian plates”

2. Leaves a gap3. High temperature and pressure in mantle forces the magma to rise from mantle to fill the gaps4. Magma cools and solidifies5. Forming mid-oceanic ridge/volcano

O-C, O-O convergent

1. Describe the kind of movement & Identify the plates: “Convergent plate movement of oceanic plates ---N. American and Eurasian plates”. State which subducts, is denser, why and how.

2. Under intense heat and pressure in the mantle, the tip of the subducted plate melts to become magma,

3. which then rises to the earth’s surface through fractures in the crust4. Magma cools and solidifies5. Forming volcano

How to draw nice Plate Tectonic diagrams

1. Label ● “oceanic plate”, “continental plate” (o-o, o-c convergent: state which is denser), or actual names (e.g. S. American plate)

● “volcano” or volcano name given● “Sea”● “Tip of subducted plate melts”● “rising magma”

2. Arrows ● to show divergence and convergence (in Key, show it means “direction of plate movement”)

● to show the rising magma

3. Draw ● the tip of subducted plate JAGGED● for the layers of the volcano DIAGONAL DOWNWARD LINES

4. BASICS ● INCLUDE A TITLE. ● DRAW THE DIAGRAM ACCORDING TO THE QUESTION.

○ If the question asks for “Features formed when an oceanic and continental plate converge”, draw an oceanic trench, a volcano and fold mountains. (and note: fold mountains are only formed AFTER the volcano is formed.)

○ If the question asks ONLY for the volcano, draw only the formation of the volcano

VolcanoesEffects of a Volcanic Eruption

Type of Effect

Effects (-) Why people still want to stay near volcanoes (-)

Physical Forests destroyed due to pyroclastic flow Trees blown down due to ash and volcanic bombs Aquatic ecology negatively affected due to pollution by mudflows

Fertile soil: Ash deposits and lava weathered become fertile soil rich in phosphorous.--> crops can be grown. Eg. Java, Indonesia

Economic Loss of revenue for farms – farms destroyed Funds channeled to rebuilding – buildings infrastructure destroyed Disruption of ecnomic activities caused by damage in transport infrastructure: a)Air flights cancelled – vision and engine failure possibility due to ejected ash and state of country itself, b) transportation systems (trains/roads/bridges) destroyed due to lava/pyroclastic flow ---> lead to business disruptions, exports/imports affected

Increased income for farmers due to increased output from fertile soil

Generation of geothermal power (electricity) tapping on the steam.Eg. Iceland, 80% heating needs are tapped from geothermal power Rich mineral content (mines) to sell.Valuable minerals and precious stones such as diamonds found in volcanic rocks. e.g. diamond and copper mining are carried out in the volcanic regions of Kimberley in South Africa.

Increased income due to tourism industry by interesting volcanic landforms can lead to the development of the tourism industry.

e.g. the volcanic island of Hawaii have attracted many tourists from all over the world.

Social Loss of recreational ground as mudflow pollutes rivers Temporary standard of living lowered – homes less people, no accommodation, no jobs (refer to points about economy being affected mentioned), no efficient transportation Respiratory problems – ejected ash from volcanic eruption remains in the air, haze

Availability of jobs – volcanic areas may have hot springs, repair work Strong sense of rootedness to the place – after staying for a long period of time, they are resistant to the idea of a new unfamiliar place Confidence in scientists – People believe the scientists’ prediction will be accurate and that they will be able to evacuate in time

Lack of money - Many are subsistence farmers and most barely have money to move elsewhere

Generalisations of Effects:● +/- ve● scale (to whom?)● PPECS aspects● e.g.: The negative consequences of the volcanic eruption in terms of economic, social and

physical aspects, are not limited to European countries but also countries further away.Measures to Alleviate Effects1. Scientists try to predict the next eruption. They do this by tracking seismic movements, carefully studying past eruptive history of volcano for a pattern and monitoring for eruption precursors in the vicinity. By doing so, they may predict the time/place of the eruption and evacuate the people so there will be no loss of lives. 2. Build hazard-resistant structures. They can have Strong roofs and steep-sloping sides designed to shed ash3. Be more effective in emergency response. depends on: Pre-emergency training and education, information and warning system, simple alert system

○ For example, for the Sichuan earthquake, the Chinese government could have been more effective in emergency response. This could be done by educating the public on how to respond/evacuate during an earthquake, holding safety drills and using sirens instead of phones as an alert system.

Types

Characteristic Basic Lava Acidic Lava

Viscosity of lava Low High

Sticky/non-sticky Non-sticky Sticky

Amt. of silica Low High

Speed of lava flow (because of viscosity)

High Low

Temperature Higher Lower

Distance of lava flow Long (Temp. high-->takes longer to solidfy)

Short (Temp. lower-->solidifies easily)

Rate of gas and steam escaping magma/ Eruption

Quiet because less viscuous More explosive because solidified lava block the vent

Volcano formed Gentle-sloping shield volcano (lava covers larger areas due to speed and slower to solidify)

Steep coned composite volcano (lava covers smaller areas due to speed and fast solidify)

Damage Potential ● Fire threat● Strength sufficient to

destroy most structures● Buoyancy effect may lift

and transport objects● May dam rivers and

modify drainage ● noxious haze generate by

sustained lava eruptions, lead to respiratory problems

- Force of impact extremely destructive- High velocity ensures no possibly to humanly escape- Can overcome 1000m high topography

Examples Mount Loa, Hawaii Mount Mayo, Philipines(composite, more common)

Distribution 1. Chain of volcanic islands - along convergent plate boundaries where subduction takes place2. Submarine/undersea volcanoes - along divergent plate boundaries where sea floor spreadman3. Groups of volcanoes - away from plate boundary, plate moving over fixed ‘hot spots’

Eruption More explosive when:1. Lava’s viscosity is higher2. Amount of dissolved gases is greater

Earthquakes-> Vibration of Earth’s surface by sudden release of energy stored in rocks in the crust.Why does it happen?1. As tectonic plates move across each other, they exert friction on each other, causing pressure to build up at their boundaries.2. Pressure gradually builds up in the plates and energy is stored up in the Earth’s crust.3. When the rocks in the crust finally can no longer contain the pressure, energy is released. This energy radiates out in shock waves through the crust and onto the Earth’s surface. Large faults will also occur as the rocks break up and move in a series of sudden jerks.

Characteristics:

Focus -> point of release of energy within Earth’s crustEpicentre -> point on the Earth’s surface that lies directly above the focus

Effects● Huge fires

○ This is caused by damage wires, overturned stoves or broken gas pipes when ground shakes

● Collapse of infrastructure/weakening of foundation of infrastructure ○ Common occurrence during earthquake in populated area○ Especially in places where infrastructure isn’t built to withstand earthquakes○ May weaken foundation if earthquake is not strong enough to collape infrastructure

● Landslides○ When the ground shakes, the soil on hill slopes loosens, leading up to landslides

● Tsunamis○ A series of huge waves produced as a result of undersea earthquakes

Post-Effects● Loss of lives

○ Result directly from fires, landslides, tsunamis or collapse of infrastructure● Negative economic impacts

○ Due to destruction of infrastructure ■ Buildings, roads, water pipes and electrical supplies caused great inconvenience to

businesses■ Repair and rebuilding costs

● Spread of diseases○ Homeless people are put in temporary shelters like schools and tents -> these are

overcrowded and lack proper sanitation -> rapid spread of diseases (eg. cholera)○ Dead bodies and poisonous materials from broken sewage pipes pollute water supplies ->

water-borne diseases● Trauma● Disruption of jobs

○ Fishermen and fishers whose jobs are dependent on the physical environment○ Tourists avoid visiting places where earthquakes have occurred

Factors influencing Extent of Damage1. Level of preparedness -> Lack of communication, slow response of government2. Density of buildings -> Very densely populated and highly built up -> Fire spreads easily3. Types of buildings -> Filmsy; Made of wood (eg. traditional homes in Japan) -> Fire spreads easily4. Fires and floods5. Time of day

● Early in the morning - people are still sleeping -> slow reaction● Midday - people are working, out on the streets -> chaotic● Night - low visibility -> rescue work hindered

Level of development:● preparedness

● education● drills put in place previously - possibility as it has happened before

○ Japan is an earthquake-prone country○ Japan knows it is dangerous

● level of technology (linked to the level of development of the country!) :response, rescue efforts, Objects and facilities available (emergency supply)

● Infrastructure (density of building-can spread fire)● level of technology (ability/efficiency in predicting disaster):

○ scientists track seismic movements to alert the people■ monitoring■ predicting the place/time

Generalisation: The extent of negative social, economic and physical impacts brought about by earthquakes is dependent on the level of development and physical characteristics of the country.

Writing generalisations● Conclusion/Summary● Majority view: No precise details or specific examples, such as: Infrastructure, preparedness,

efficiency, magnititude● positive / negative impact● Show scale● “extent”● Categories (PPECS)● Statement -> One sentence

e.g.: The extent of negative social, economic and physical impacts brought about by earthquakes is dependent on the level of development and physical characteristics of the country.Photo Interpretation

With reference to the figure above only, describe how the eruption of Mt Pinatubo has impacted both the physical environment and the people living in the area.[6]6 points

People living in the area● Loss of homes. This is due to the relocation of all inhabitants living within 20 km of the summit and

also the destruction of their homes by the “Flows of mud and ash sweep downhill, covering several villages”. The villagers have rootedness to their homes since they have lived there for generations, e.g. subsistence farmers. Hence, they will lose their sense of belonging to the place.

● Loss of income for rice farmers, employees at Clark Air Base. As seen, the rice farms in Middle Third (within 10 km of summit) and Clark Air Base in Background Third, were evacuated on 7 June on Alert Level 4. Not being able to work, farmers and employees at the Air Base will lose their source of income. At their relocated city, Angeles City or Culayo, the situation is aggravated because they do not have the skills needed to get a non-agricultural job and there may not be enough job vacancies. Therefore, rice farmers and employees will not get income.

● Respiratory problems for people not only living in the area but also nearby cities like the Angeles City and Culayo. During the volcanic eruption, clouds of steam, hot gas and dust over 30m high, as well as volcanic bombs and ash are released. Winds blow these ejected materials over long distances, which approaches the nearby cities as a haze, causing respiratory problems like asthma and bronchitis

● Loss of lives. Hot gases, ash and gases flowing at 100km per hour, also known as a pyroclastic flow, will very quickly reach the nearby cities which are only 25km away. As the flow will reach the cities before the citizens manage to evacuate, they will get killed due to severe burns and inhalation of gases like sulphur dioxide.

Physical environment● Plants growing at the rice farming area will get wiped out. This is due to the acidic lava being

ejected from the eruption. Most plants are not able to survive under such levels of acidity. (Short term)The soil near the volcano becomes more fertile. Volcanic ash is ejected during an eruption, and over the long term,Ash deposits and lava weathered become fertile soil rich in phosphorous, whiich is very fertile soil (Long term): Crops can be grown. Eg. Java, Indonesia