Presentation on theme: "GCSE Revision session. Tectonic activity With Mr Thompson."— Presentation transcript:
GCSE Revision session. Tectonic activity With Mr Thompson.
Introduction. Paper 1 –Physical Geography. Make sure you know key terms Make sure you know: features, how they are formed, the effect they cause, advantages and disadvantages to human life. Human responses and that you can relate it to actual places.
This unit can be split into 3 sections. Often one will affects another. They are: The earths structure. Volcanoes Earthquakes.
The Earths structure. Activity 1 on the earths outline label on the following: Mantle Outer core Inner core Crust Mantle Plates
The CRUST is made up of interlocking slabs of rock called PLATES which are moving and float on the MANTLE. They can be CONTINENTAL or OCEANIC
OCEANIC CRUST - Under the oceans, Dense (heavy), thin and gets destroyed at SUBDUCTION ZONES and created at CONSTRUCTIVE BOUNDARIES. CONTINENTAL CRUST - Under the continents, lighter, thicker and permanent.
PLATE MOVEMENT - caused by CONVECTION CURRENTS in the MANTLE. PLATE BOUNDARY - Where two plates meet. Most of the world's EARTHQUAKES and VOLCANOES are found on plate boundaries.
TYPES OF PLATE BOUNDARY COMPRESSIONAL. Where two plates move towards each other. Two types:- DESTRUCTIVE - Where oceanic crust moves towards continental crust and is destroyed at the Subduction Zone. Earthquakes and Volcanoes are violent and Fold Mountains are found eg West coast of South America where Nazca plate meets South American plate.
COLLISION Where two Continental plates collide. Fold Mountains are formed. There are earthquakes, but no volcanoes. Eg Himalaya's
TENSIONAL or CONSTRUCTIVE Where two oceanic plates move apart and new crust is formed. The earthquakes and volcanoes are more gentle. Can create a mid-ocean ridge eg The Mid Atlantic Ridge.
CONSERVATIVE Where two plates slide past each other. Friction between the plates can cause pressure to build up that can lead to violent earthquakes when it is released. Eg San Andreas Fault.
WHAT CAUSES FOLD MOUNTAINS TO BE FORMED ? Convection currents cause two plates to move towards each other. Pressure causes a large downfold called a GEOSYNCLINE. Erosion leads to sediments being deposited in the geosyncline. Sediments build up and are compressed. Pressure from the moving plates cause the sediments to fold. As movements get more violent fold mountains are formed.
HOW DO FOLD MOUNTAINS INFLUENCE HUMAN ACTIVITY? ADVANTAGES Income from tourism eg skiing in winter and hill walking/climbing/mountain biking in summer. Hotels, Bed & Breakfast, Campsites. Pleasant environment to live in. Employment in farming, forrestry & HEPGrowth in tourism reduces out migration.
DISADVANTAGES Tourism can cause increase in traffic, buildings which spoil the scenery, increase in house prices, pollution and footpath erosion. Difficult communications, often remote areas. Lack of industry for alternative employment. Wildlife affected
WHAT CAUSES A VOLCANIC ERUPTION? OCEANIC crust moves towards CONTINENTAL crust. The OCEANIC crust is forced under the CONTINENTAL CRUST Friction and heat from the mantle melts the OCEANIC crust MAGMA is forced upwards through weak points in the rock. Pressure build up leading to violent volcanic eruptions.
Activity 2. Draw and lable the STRUCTURE OF A VOLCANO with the following; CRATER ASH, BOMBS & GASSES, (PYROCLASTS) LAVA FLOW MAIN VENT LAYERS OF ASH AND LAVA SECONDARY OR PARASITIC CONE DYKE EARTH'S CRUST MAGMA CHAMBER
Crater Ah, bombs and gases (Pyroclasts Lava flow Main Vent Secondary or parasitic cone Dyke Magma chamber Earths crust Layers of ash and lava
Key Phrases. ACTIVE VOLCANO - Erupts regularly or recently eg Stromboli, Montserrat, Mt. St. Helens or Mt. Pinatubo. DORMANT - Has not erupted for a long time (about 2000 years) EXTINCT - Volcano that no longer erupts MAGMA - Molten rock that becomes LAVA when it reaches the surface of the earth. NUEE ARDENTE - A volcanic cloud of gas, steam and ash. E.g. eruption of Mt. St. Helens, Mt Etna or Montserrat.
WHY ARE VOLCANOES DIFFERENT SHAPES? STEEP SIDES - Due to the lava being VISCOUS (thick). This lava is also known as ACID lava and is rich in SILICA. They are found on DESTRUCTIVE Plate Boundaries eg VESUVIUS. ASH volcanoes are also steep sided. COMPOSITE (a mixture of ash and lava)
GENTLE SIDES Lava is NON-VISCOUS (runny) or BASIC. They are called SHIELD volcanoes eg MAUNA LOA (HAWAII). They are found on CONSTRUCTIVE Plate Boundaries. They are less explosive.
A CALDERA A large crater caused by the top of a volcano being blown off or the cone collapsing into the VENT eg CRATER LAKE, USA.
EFFECTS OF VOLCANOES SHORT TERM Ash falls on nearby farmland villages and towns. Torrential rain = LAHARS and MUDFLOWS (water picks up huge amounts of ash). Ash can cause buildings to collapse eg houses, factories, schools & hospitals. Lava can destroy anything in its path. Eruption can kill people close to the volcano. Roads and bridges become impassable. Power suppies cut off Water supplies contaminated
LONG TERM Crops destroyed by ash and lava and prevented new crops being planted. People forced to move away to other towns and cities often into shanty towns. People evacuated to refugee camps where diseases can spread very quickly. Farm animals killed. There can be long term effects on the climate eg delay global warming.
WHY DO PEOPLE LIVE NEAR VOLCANOES? FERTILE SOIL - Volcanic ash eventually breaks down to form very fertile soil eg rice grown around Mt. Pinatubo and Vineyards & Orange groves around Mt. Etna.
TOURISM - Potential income from people watching eruptions (eg Stromboli) or visiting dormant and extinct volcanoes. GEOTHERMAL POWER - Countries like Iceland can generate most of the power they need through geothermal energy. Other reasons: People do not realise the risk of an eruption. In many LEDC's land is in short supply - it may be the only available land. Scientists or Vulcanologists carrying out research on volcanoes
Key words. FOCUS - Point in the earth's crust where the earthquake starts. EPICENTRE - Point directly above the focus on the surface of the earth where the damage is greatest. SEISMOGRAPH - Instrument that measures the strength of the shockwaves. RICHTER SCALE - Scale used to measure an earthquake by the strength of its shockwaves. MERCALI SCALE - A way of measuring the strength of an earthquake by the damage it does. SHOCKWAVES -Movements in the earth's crust caused by the earthquake. AFTERSHOCKS - Smaller shockwaves that follow the main earthquake.
EFFECTS OF EARTHQUAKES SHORT TERM People killed and injured. Old buildings not built to withstand earthquakes collapsed. People made homeless Huge fires caused by broken gas pipes Buildings weakened by original earthquake destroyed by aftershocks. People die due to disease, shock and hypothermia Liquefaction where ground becomes like quick sand. Fire service unable to control fires due to lack of water caused by broken mains.
LONG TERM Communication links destroyed Employment lost due to destruction of factories e.g. Kobe = 2 Toyota factories. Kobe's port severely disrupted.Damage estimated to cost $80 billion Areas still without services for periods of 12 months and more.
HOW DO PEOPLE RESPOND TO EARTHQUAKES AND VOLCANOES? They build buildings that are strengthened with steel to withstand earthquakes. They are designed to sway. They avoid building on clay and sand. In Japan there are now monitors that will stop the railways, turn off the gas as soon as the primary waves are felt. By mapping previous earthquakes and plotting the regularity of earthquakes it is possible to estimate when the next earthquake may strike. By monitoring earth movements and gas emissions it is possible to forecast volcanic eruptions eg Mt. Pinatubo in the Phillipines. Emergency planning eg in Japan where they hold a Disaster Day when everyone practices what to do if an earthquake strikes. There are simulators where people can experience an earthquake. Posters telling people what to do in an earthquake.
WHY ARE MORE PEOPLE LIKELY TO DIE IN LEDC's THAN IN MEDC's? Less medical and relief support available. Poorer communications often mean that access to affected areas is more difficult. Housing is often of poorer construction, more likely to collapse or catch fire. Lack of money to provide instruments or technology to predict disasters or limit there effects. Poorer medical and emergency services and lack of emergency equipment. Many people in LEDC's are subsistence farmers and if their crops are destroyed they have nothing else. Power and water supplies may be disrupted allowing disease to break out and spread quickly.
Location: Bam in Iran Date: 26 December, 2003 Strength of earthquake on the Richter scale: 6.6 Number dead: 28,000
Location: California in USA Date: 22 December, 2003 Strength of earthquake on the Richter scale: 6.5 Number dead: 28,000
Here are some other reasons why the earthquake in Iran was so bad: The houses in Iraq were badly built. They were made from mud brick which collapsed straight away. When mud brick collapses it disintegrates. This leaves less air pockets, which might have allowed some people to survive, even though they were trapped.
The time of day when the earthquake happened was also important. In Bam, it happened at 5 o’clock on a Friday morning. Friday is the Muslim day of rest. Where do you think most people were, and why did they die? These are like the mud brick buildings that collapsed in Bam
Buildings like this in a rich country might topple, but they don’t crumble. What would be your chance of survival in this situation?