Living With Tectonic Hazards KQ2 Flashcards
How are fold mountains formed?
Fold mountains are formed along convergent plate boundaries. The compressional force causes the layers of rocks to buckle and fold and this process is know as folding. The crust is uplifted to form fold mountains.
Describe the distribution of fold mountains around the world.
Fold mountains are found along convergent plate boundaries. Examples are The Himalayas in South Asia, The Alps in Southern Europe, The Andes along the Western Coast of South America and The rockies along the Western Coast of North America
How are rift valleys and block mountains formed?
Rift valleys and block mountains are formed at divergent plate boundaries. The tensional forces result in part of the crust being fractured, which is called faulting. Faulting forms fractures in the rocks along which the rocks are displaced. A rift valley is formed with the central block sinking relative to the surrounding blocks and the block mountains are the blocks of crust left standing above the valley.
How are volcanoes formed?
Magma is formed by the melting of mantle and crust at divergent and convergent plate boundaries. The magma rises through the faults in the earth’s crust and emerges onto the earth’s surfaces as lava. The lava solidifies and over successive eruptions, a volcano is formed.
Shield volcanoes vs Stratovolcanoes (Silica content)
Shield volcanoes are made of low-silica lava with lower viscosity while Stratovolcanoes are made of high-silica lava with higher viscosity.
Shield volcanoes vs Stratovolcanoes (Explosiveness).
Shield volcanoes allow gases to escape easily and flow more easily through the vent and hence erupts effusively (not explosive). Stratovolcanoes trap gases more easily which results in pressure building up below the earth’s surface and erupts explosively ejecting ash and rock fragments.
Shield volcanoes vs Stratovolcanoes (Viscosity/Shape and height)
Lava ejected from shield volcanoes flow over a larger area before solidifying which forms volcanoes with gently sloping sides and a broad summit (has a convex profile). Lava ejected from stratovolcanoes flow over a smaller area before solidifying which forms volcanoes with steeper sides and narrow summit (has a concave profile).
Describe the distribution of volcanoes.
Volcanoes are mostly found in convergent plate boundaries. Examples of this are the west coast of North and South America, along the western side of the Pacific Ocean and The Mediterranean. They can also be found in divergent plate boundaries. Examples of this are the middle of the Atlantic Ocean and in East Africa, along the Great Rift Valley.
Describe the of risk living near volcanic area that is the destruction by volcanic materials.
Lava which has temperatures between 700 to 1200 C burns anything in its path. Pyroclastic flows of hot ash, rock figures and super-heated steam flow down the volcano under the force of gravity and can travel up to 80km/h destroying everything in its path. Volcanic bombs are rocks ejected forcefully during an eruption causing damage to property. These can range in size from a few centimeters to the size of cars. Landslides can occur due to the structural collapse of a volcanic cave during an eruption. The landslides can obstruct the flow of rivers which causes floods, block roads, and bury villages and farmlands. This may hamper rescue efforts from reaching affected areas and may destroy the livelihood of many farmers. For example, the ongoing eruption of Kilauea in Hawaii since 1983 of low-silica lava, which has flowed over long distances and destroyed many houses and roads.
Describe the risk of living near volcanic area that is pollution.
Ash particles from the eruption may block sunlight, suffocate crops, and cause respiratory failure for people and animals. The release of gases like sulphur dioxide and carbon monoxide may also be harmful to people. The volcanic ash can block out the sunlight and visibility making it a transport hazard. For example, an eruption of a volcano in Iceland in 2010 produced an extensive cloud of volcanic ash, which posed a serious danger to aircraft. This resulted in the closure of air space over much of Europe and caused many flights to be cancelled.
Describe the benefit of living near volcanic areas that is fertile volcanic soil.
Lava and ash from the volcanic eruptions break down to form fertile volcanic soils making it favourable to agriculture. People can grow more crops here than elsewhere and can earn an income selling their excess crops. For example, the reason why the islands of Java and Bali have been able to support large rural populations over many decades is due to the volcanic soils which have made it possible to support the cultivation of crops.
Describe the benefit of living near volcanic areas that is building materials, and precious stones and minerals.
Volcanic rocks can be rich in precious stones and minerals. These resources can only be formed in a volcanic area after millions of years. People living around volcanoes can earn a living mining these materials and precious stones. For example, Diamonds are created deep underground and are brought close to the surface when magma forces its way upwards from the mantle. Old volcanic rocks at Kimberly South Africa are one of the world’s richest sources of diamonds.
Describe the benefit of living near volcanic areas that is tourism.
Volcanic areas offer a variety of activities for tourists to engage in. People visit volcanoes because of their beautiful scenery. They are also places rich in history. People living around volcanoes can make a living providing services such as accommodation, food, guiding and souvenirs to tourist who visit the area. For example, Pompeii was partially destroyed and buried under 4 to 6m of ash and pumice in the eruption of Mount Vesuvius in CE 79 and is now a major tourist attraction in Italy.
Describe the benefit of living near volcanic areas that is Geothermal energy.
Geothermal energy is derived from the heat in the earth’s crust. When ground water comes into contact with hot rocks beneath the surface, it heats up and may change to steam. The hot water or steam can be harnessed to produce electricity. For example, over 70% of Iceland’s homes are heated by volcanic steam and most of Iceland’s electricity is generated from geothermal power due to the large number of volcanoes in the country.
How do earthquakes occur?
When plates diverge, converge or move past each other, the movement is not smooth. This results in the slow buildup of stress on the rocks on either side of the faults. When the rocks can no longer withstand the increasing stress they can suddenly break and move many meters. This results in the sudden release of stored energy in the rocks found along fault lines causing an earthquake. The energy released travels along the surface of the earth causing it to shake violently.
