Destructive effects of volcanism:
- Volcanism can be a greatly damaging natural disaster. The damage is caused by advancing lava which engulfs whole cities. Habitats and landscapes are destroyed by lava flows.
- Showers of cinders and bombs can cause damage to life.
- Violent earthquakes associated with volcanic activity and mud flows of volcanic ash saturated by heavy rain can bury nearby places.
- Sometimes ash can precipitate under the influence of rain and completely cover the surrounding regions.
- Health concerns after a volcaniceruption include infectious disease, respiratory illness, burns, injuries from falls, and vehicle accidents related to the slippery, hazy conditions caused by ash.
- Further effects are the deterioration of water quality, fewer periods of rain, crop damages, and the destruction of vegetation.
- In coastal areas, seismic sea waves called tsunamis are an additional danger which are generated by submarine earth faults where volcanism is active.
Positive effects of volcanism:
- Volcanism creates new landforms like islands, plateaus,volcanic mountains etc. For example: Deccan plateau, Mt. Vesuvius.
- The volcanic ash and dust are very fertile for farms and orchards.
- Volcanic rocks yield very fertile soil upon weathering and decomposition.
- Although steep volcano slopes prevent extensive agriculture, forestry operations on them provide valuable timber resources.
- Mineral resources, particularly metallic ores are brought to the surface by volcanoes. Sometimes copper and other ores fill the gas bubble cavities. The famed Kimberlite rock of South Africa, source of diamonds is the pipe of an ancient volcano.
- Lava rock is extensively used as a source of crushed rock for concrete aggregate or rail road ballast, and other engineering purposes
- In the vicinity of active volcanoes, waters in the depth are heated from contact with hot magma giving rise to springs and geysers. The heat from the earth’s interior in areas of volcanic activity is used to generate geothermal electricity.
- Countries producing geothermal power include USA, Russia, Japan, Italy, New Zealand and Mexico.
- At many places volcanic landforms attract heavy tourist traffic. At several places national parks have been set up centred around volcanoes.