Physical GEOG: Chapter 4 - Plate Movements
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Physical GEOG: Chapter 4 - Plate Movements

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Physical GEOG: Chapter 4 - Plate Movements Physical GEOG: Chapter 4 - Plate Movements Document Transcript

  • Folding occurs typically at convergent plate boundaries where layers of rock are pushed and compressedcausing rock strata to buckle and fold, forming fold mountains.Faulting involves the displacement of rock strata along fault lines or large cracks in the Earth’s crust toform block mountains and rift valleys.Distribution of…Fold mountains Fold mountains are found along convergent plate boundaries. They are found where two continental plates collide or where one continental plate converges with an oceanic plate. There are two major fold mountain belts. One belt is the Circum Pacific belt that surrounds the Pacific Ocean. In the eastern part of the Pacific Ocean, the mountains are found mainly along the edge of continents such as the Andes and Rockies. In the western part, they are found offshore and take the form of island arcs such as Japan and Philippines. The other belt is the Mediterranean-North India belt stretching from northen part of Africa where Atlas mountains are to Southern Europe where the Alps are to Northern India where the Himalayas are.Volcanoes Volcanoes are mostly found in belts that coincide with convergent and divergent plate boundaries. 15% of the volcanoes are found at mid-oceanic ridges and 80% of them are found at subduction zones all of which are places with high plate activity. At divergent plate boundaries, basaltic volcanoes and volcanic islands form on mid- oceanic ridges or ocean floors. For example, Iceland and Surtsey Island are on the Mid-Atlantic Ridge. At convergent plate boundaries, subduction volcanoes are found especially in the Circum Pacific region. For example, Mt St Helens on the Rockies, Philippine Islands and Aleutian Islands. 5% of the world’s volcanoes are formed over hot spots for example Mauna Loa in Hawaii.Earthquakes The world’s major earthquakes occur along all 3 plate boundaries – convergent, divergent and transform – where they represent zones of instability in the Earth’s crust. One major belt is the Circum Pacific belt that surrounds the Pacific Ocean. It coincides with regions with subduction volcanoes, oceanic trenches and fold mountains. This accounts for 68-70% of all earthquakes. The other belt is the Mediterranean-North India belt
  • which stretches from Southern Europe where the Alps are to Northern India where the Himalayas are. They account for about 20% of earthquakes. The 3rd belt is the Mid-Atlantic belt and the East African Valley where divergence of plates cause them. This accounts for about 10% of earthquakes.Formation of rift valleys (I) Rising and spreading magma generates convectional currents which result in continental-continental plate divergence of the (plate name) and (plate name). As the crust continues moving apart, they are stretched, causing fractures to form near the boundary. Tensional forces cause normal faults to appear. The land between the crusts sinks as a result forming a linear depression known as the rift valley.Formation of rift valleys (II) Cooling and sinking magma generates convectional currents which result in continental-continental plate converge of the (plate name) and the (plate name). As the crust continues moving together, they are compressed, causing fractures to form near the boundary. Compressional forces cause reverse faults to appear. The land beside the faults are raised making the middle block appear lower. The overhanging escarpments are soon eroded by wind and the land between the faults form a linear depression known as the rift valley.Formation of block mountains (I) Rising and spreading magma generates convectional currents which result in continental-continental plate divergence of the (plate name) and (plate name). As the crust continues moving apart, they are stretched, causing fractures to form near the boundary. Tensional forces cause normal faults to appear. The land beside the faults subside making the middle block appear appear higher. The land left higher is the block mountain.Formation of block mountains (II) Cooling and sinking magma generates convectional currents which result in continental-continental plate converge of the (plate name) and the (plate name). As the crust continues moving together, they are compressed, causing fractures to form near the boundary. Compressional forces cause reverse faults to appear. The land between the faults are raised. The overhanging escarpments are soon eroded by wind and the land between the faults form a block mountain.
  • Characteristic Shield volcano Acid volcano Composite volcanoShape Gently sloping, flat Steep slopes, narrow Steep slopes at top, near top, broad base. base. gentle slopes at bottom. Finer ash and cinder are blown by wind down (wind sorting)Type of lava Basic lava: low Acid lava: high Acid lava: high viscosity, high viscosity, low viscosity, low temperature, take long temperature, take short temperature, take short time to solidify time to solidify time to solidifyMaterials ejected Gas, steam, basic lava. Acid lava only Acid lava, cinder, ash that forms alternating layers.Type of eruption Non-violent, basic lava Violent, acid lava Violent, acid lava travels a long distance travels very little hence travels very little hence before it solidifies hence it solidifies near the it solidifies near the it does not clog up the vent, clogging it up. vent, clogging it up. vent of the volcano Pressure due to gases Pressure due to gases which means that lava builds up resulting in builds up resulting in can escape easily. violent eruptions. violent eruptions.Diagram of volcano, eg eg. Mauna Loa, Hawaii eg. Mt Mayon, eg. Mt Vesuvius, Italy Philippines View slide
  • Type of impact Impact Description Example Lava and pyroclastic People still live at the material may be slopes of Mt Merapi, weathered down to form Indonesia as the Fertile soil for soil for agriculture, pyroclastic materials agriculture expedited in tropical make the soil near the areas. Minerals released slopes extremely make it easy for farmers fertile. to reap rich harvests. Vulcanicity may form precious stones and Precious stones and minerals such as gold, - minerals silver, diamonds etc enabling mining to be carried out. Benefit Volcanic areas appeal to People in Japan bury tourists as they would like themselves in to see volcanic landforms volcanic materials as and also volcanic hot they believe these Tourism springs can be converted materials help them to to health resorts as relax and can cure mineralised water is some ailments. believed to have medicinal value. Steam produced from hot underground water in volcanic areas can be Geothermal energy harnessed to drive - turbines to generate electricity, alternative source of electricity. Sulfur dioxide released by volcanic eruptions react with oxygen in the air to form sulfur trioxide Problem Acid rain which soon reacts with - water vapour to form sulfuric acid that mixes with rainwater to corrode infrastructure and leaches soil. View slide
  • Sulfate aerosols may block incoming solar radiation, cooling the troposphere and resulting in a ‘cooler’ Earth. They Effects on weather - also block outgoing heat radiation from the Earth’s surface, warming the stratosphere (enhanced greenhouse effect) Large amounts of ash andProblem dust extruded during the volcanic eruption may pollute the environment, block the sun and make day dark, disrupting transport networks. Ash Pollution - may remain in the air damaging the respiratory systems of people and livestock. It may also mix with water sources hence reducing available clean water sources.