(a) Define the term Vulcanicity (b) Describe the mode of formation and appearance of a volcanic plateau (c) Highlight four effects of Vulcanicity

Answer Details

(a) Meaning of Vulcanicity

Vulcanicity (vulcanism) is the process by which molten rock (magma), gases and other volcanic materials from the interior of the Earth are forced towards or onto the surface. It includes both intrusive activity (magma cooling within the crust to form features such as batholiths, dykes, sills and laccoliths) and extrusive activity (lava and materials reaching the surface to form volcanoes, lava plateaux and geysers).

(b) Formation and appearance of a volcanic (lava) plateau

Mode of formation: A volcanic plateau is formed by fissure eruptions. Very fluid, basic (basaltic) lava wells up quietly through long cracks or fissures in the crust rather than from a single vent. Because the lava is thin and runny, it spreads out over a wide area before cooling. Repeated eruptions build up layer upon layer of solidified lava (basalt) until a thick, extensive, raised, flat-topped upland is formed.

Appearance: It appears as a broad, high, almost level or gently undulating tableland with steep edges. It is built of horizontal sheets (layers) of basalt, and rivers later cut deep gorges and valleys into it. Examples include the Jos Plateau region basalts, the Ethiopian (Abyssinian) Plateau and the Deccan Plateau of India.

(c) Four effects of Vulcanicity

• Fertile soils: weathered volcanic (lava) materials give rich soils good for farming crops such as coffee, tea and cocoa.
• Landform and scenic value: it creates mountains, plateaux, crater lakes and hot springs that attract tourists.
• Mineral and geothermal resources: volcanic areas yield useful minerals and provide geothermal energy (steam/hot springs) that can generate electricity.
• Hazards: violent eruptions destroy life, farmland and property, and can cause earthquakes and force people to migrate.