That’s a good question. I guess the main good effect that volcanoes have on the environment is to provide nutrients to the surrounding soil. Volcanic ash often contains minerals that are beneficial to plants, and if it is very fine ash it is able to break down quickly and get mixed into the soil. Volcanoes have also done wonderful things for the Earth. They helped cool off the earth removing heat from its interior. Volcanoes make islands and add to the continents.
Perhaps the best place to look for more information about this would be to look up references about some of the countries where lots of people live in close proximity to volcanoes and make use of the rich soils on volcanic flanks. These would include Indonesia, The Philippines, Japan, Italy, etc.
I suppose another benefit might be the fact that volcanic slopes are often rather inaccessible, especially if they are steep. Thus they can provide refuges for rare plants and animals from the ravages of humans and livestock.
Finally, on a very fundamental scale, volcanic gases are the source of all the water (and most of the atmosphere) that we have today. The process of adding to the water and atmosphere is pretty slow, but if it hadn’t been going on for the past 4.5 billion years or so we’d be pretty miserable.
Volcanic deposits are also used as building materials. In the 1960′s Robert Bates published Geology of the Industrial Rocks and Minerals. He noted that basalt and diabase are quarried in the northeastern and northwest states. Most of the basalt and diabase is used for crushed stone: concrete aggregate, road metal, railroad ballast, roofing granules, and riprap. High-denisity basalt and diabase aggregate is used in the concrete shields of nuclear reactors. Some diabase is used for dimension stone (“black granite”).
Pumice, volcanic ash, and perlite are mined in the west. Pumice and volcanic ash are used as abrasives, mostly in hand soaps and household cleaners. The finest grades are used to finish silverware, polish metal parts before electroplating, and for woodworking. Bates reports that in ancient Rome lime and volcanic ash were mixed to make cement. In modern times pumice and volcanic ash have been used to make cement for major construction projects (dams) in California and Oklahoma. Pumice and volcanic ash continue to be used as lightweight aggregate in concrete, especially precast concrete blocks. Crushed and ground pumice are also used for loose-fill insulation, filter aids, poultry litter, soil conditioner, sweeping compound, insecticide carrier, and blacktop highway dressing. Perlite is volcanic glass (made of rhyolite) that has incorporated 2-5% water. Perlite expands rapidly when heated. Perlite is used mostly as aggregate in plaster. Some perlite is used as aggregate in concrete, especially in precast walls.
Source of Information:
Bates, R.L., 1969, Geology of the Industrial Rocks and Minerals: Dover, NY,459 p.
Pros and Cons of Volcanoes
- Create new islands and land.
- Volcanic materials form some of the most fertile soils on Earth
- Provide isolated habitat to pioneer species.
- Create economic mineral deposits.
- Create beautiful landscapes.
- Generate tourism.
- Destroy old habitat and crops.
- Destroy cities, towns, communities.
- Displace populations.
- Kill people and other animals.
- Disrupt commerce.
- Generate tsunami.