what are the constructive and destructive effects of volcanic eruptions?

Question

i would prefer a detailed answer, or a link to any document dealing with this subject (cons. & des. efects) as i need it for a project

Answer 1

Learning is found in the research. You are selling yourself short if someone else does your work. I won't tell you because I love geology and want you to discover the great wonder it really is.

Answer 2

Not all volcanic phenomena are destructive. The
oceans, atmosphere, and continents owe their
origin and evolution largely to volcanic
processes throughout geologic time.

Volcanic gases are the source of all the water (and most of the atmosphere) that we have today
Volcanic ash contains minerals which produce fertile soil
Volcanoes can provide refuges for rare plants and animals from the ravages of humans and livestock.
http://plaza.ufl.edu/sykid/

The rain from these storms melds the ash together into what is called lapilli. Total darkness may fall upon the region during the typical two day eruption. When the volatile content in the column is reduced, the column collapses, raining destruction down upon any nearby towns (as with Pompeii). The ash released into the stratosphere has proved hazardous for airplanes flying through it. Mt. Pinatubo's eruption caused at least 9 airliners to make emergency landings when the ash damaged their engines. Humans cannot distinguish between a normal cloud and the fine clouds of volcanic ash. The aerosols released by Plinian eruptions, like sulfur dioxide, changes into sulfur trioxide, and then combines with water in the air to form sulfuric acid. As a result of these substances being present in the atmosphere, temperatures are reduced when these substances reflect solar heat back into space. For 6 to 18 months after Pinatubo's eruption, parts of North America and Europe suffered from the aerosol's cooling effects. The aerosols from Pinatubo had covered the globe a year after the eruption. Tambora, another Plinian eruption, released aerosols that traveled the world for a number of years and created the year without a summer in Europe and North America in 1816. In June of 1816, New England experienced frosts and Canada's temperatures were 3 to 5 degrees below normal. Thus, it is good that Plinian eruptions are less frequent than other eruptive styles (Scarth). The diagram below depicts how frequent Plinian eruptions of various sizes are and compares them to past eruptions.

http://www.personal.psu.edu/users/l/b/lbh129/volcanoes/eruptions.htm