Theory question 303
Earth Movements and Vulcanicity(a) List two examples of volcanic mountains in the world. (b) With the aid of annotated diagram, describe how composite cones are formed. (c) Outline three causes of landslides.
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(a) Mt Kilimanjaro (Tanzania); Mt Cameroon; Mt Fuji (Japan); Mt Vesuvius and Mt Etna (Italy); Mt Kenya; Mt Mayon (Philippines); Mt St Helens (USA).
(b) Diagram: cone with alternating layers of ash and lava, central vent, crater, side (parasitic) vents. Formation: magma rises through a vent from a magma chamber; violent eruptions throw out ash, cinders and bombs which settle round the vent; quieter eruptions pour out lava which covers the ash layer; repeated alternating eruptions build up a tall cone of layers with steep concave/convex slopes; side vents may form parasitic cones.
(c) Heavy or prolonged rainfall saturating slopes; earthquakes and volcanic tremors; undercutting of slopes by rivers, waves or road cutting; deforestation; steep slopes with weak or clay rock; mining and quarrying; overloading slopes with buildings.
Label the layers in the diagram.