14.8 What are the impacts of earthquakes and tsunamis? • Earthquakes and tsunamis can affect people and result in deaths, injuries and damage to homes and infrastructure. • The impact of a tsunami or earthquake can vary greatly depending on a country’s level of income. • The environment can be affected through landslides, erosion and liquefaction. • Ground liquefaction occurs when soil suddenly loses strength and, mixed with groundwater, behaves like a liquid. 14.9 What are volcanoes and how are they formed? • Volcanoes are formed when molten magma in the Earth’s mantle is forced through an opening in the Earth’s surface. • Volcanoes can be formed in rift valleys, near convergent plate boundaries and over hotspots. 14.10 Investigating topographic maps – Mount Taranaki, New Zealand • Mount Taranaki is the largest volcano on New Zealand’s mainland, on the North Island. • Mount Taranaki is a dormant stratovolcano that is likely to erupt in the future. 14.11 What are the types of volcanoes and how do they erupt? • The shapes and sizes of volcanic landscapes depend on the type of lava, the amount of ash and the speed of the eruption. • Volcanic ash is actually tiny fragments of rock and as such it is denser and more damaging than ash from a wood fire. • A pyroclastic flow is a superheated avalanche of rock, ash and lava that rushes down the mountain. • A lahar is a flow of mud and ash that occurs when eruptions melt snow and ice, and mix with rocks and stones. 14.12 How do volcanic eruptions affect people? • Volcanic mountains form when magma erupts to the Earth’s surface. • Volcanic eruptions can destroy landscapes and kill people. • Large numbers of people across the world live near volcanoes because of the location of fertile soils, ore deposits and geothermal energy. • Predicting the type and scale of a volcanic eruption is increasingly important with over 500 million people living so close to active volcanoes. 14.13 Inquiry: Supervolcano report • What is a supervolcano? • Where are supervolcanoes located? • What could happen if a supervolcano erupted? 14.14.2 Key terms altitude height above sea level convection current a current created when a fluid is heated, making it less dense and causing it to rise through surrounding fluid and to sink if it is cooled; a steady source of heat can start a continuous current flow converging plate a tectonic boundary where two plates are moving towards each other cultural relating to the ideas, customs and social behaviour of a society divergent plate a tectonic boundary where two plates are moving away from each other and new continental crust is forming from magma that rises to the Earth’s surface between the two epicentre the point on the Earth’s surface directly above the focus of an earthquake fault an area on the Earth’s surface that has a fracture; a fault lies at the major boundaries between Earth’s tectonic plates fault plane the area of a tectonic plate that moves vertically as a result of an earthquake focus the point where the sudden movement of an earthquake begins
TOPIC14 Geomorphological processes and hazards
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