Theory question 204
Earth Movements and Vulcanicity(a) Define the term vulcanicity. (b) Describe the mode of formation and appearance of a volcanic plateau. (c) Highlight four effects of vulcanicity.
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(a) Vulcanicity is the process by which molten rock (magma) and gases are forced into the earth's crust or out onto its surface.
(b) Formation: very fluid basic (basaltic) lava pours quietly out of long fissures rather than a central vent; it spreads widely before cooling; repeated flows pile up layer upon layer over a large area. Appearance: extensive, high, flat or gently undulating surface; steep edges often cut by rivers into step-like slopes; dark basalt rock weathering into fertile soils, e.g. Deccan plateau, Columbia-Snake plateau, Jos Plateau (Biu).
(c) Formation of new landforms (mountains, plateaux, islands); fertile volcanic soils; destruction of life and property; minerals and building stone; hot springs and geysers for geothermal power; tourism; air pollution and climate change from ash; earthquakes and tsunamis.
For (b) give both how it forms and what it looks like.