The Effects Of Volcanic Activities On The Environment



The Effects Of Volcanic Activities On The Environment

Except for abundant free oxygen released from plants, algae and cyanobacteria by photosynthesis, atmospheric gases initially come from the earth's interior. Gases within magma are dissolved because of high pressures beneath the earth's surface, but reduced pressure at the surface allows dissolved gases to expand and escape. Water vapor constitutes 70 to 95 percent of all eruption gases. The rest consists of carbon dioxide, sulfur dioxide and traces of nitrogen, hydrogen, carbon monoxide, sulfur, argon, chlorine and fluorine.

The different volcanic gases effect the earth, people and animals in different ways. Water vapor is beneficial, adding to the earth's water supply. Sulfur dioxide can form aerosols that reflect the sun's rays and cause cooling of the earth's surface, or cause harm by forming acid rains. Fluorine gases and their acid aerosols can be lethal to animals. Carbon dioxide can add to the effects of global warming. There is circumstantial evidence that volcanic eruptions can affect short-term weather patterns, and possibly trigger long-term climatic change. The U.S. Geological Survey is studying volcanic emissions and global change. The effects of human activities upon global climate become important to understand as the world population grows. One of the main concerns is global warming. This could cause ocean levels to rise if the glaciers in Antarctica melt, and seriously disrupt many large population centers on earth -- London, Tokyo-Yokohama, Los Angeles, New York, Buenos Aires -- as water levels rose. If there is some evidence that man's pollutants, beyond that of natural contaminates such as volcanic gases, can cause global warming, steps should be taken to reverse the trend.

Researchers estimate that, between 1990 and 2100, there is a 90 percent probability that global temperatures will rise by 1.7 to 4.9 degrees Celsius (3.1 to 8.9 degrees Fahrenheit), because of human influences on climate. Such warming would have widespread impacts on society and the environment, including continued melting of glaciers and the great ice sheets of Greenland, inundating the world's coasts. The authors base their estimate on computer model experiments by climate scientists, observations of atmospheric changes, and recorded climate changes over the past century.

However, there is still large uncertainty in understanding the global climate and how it will change, says Karl. If temperatures rise 1.7 degrees, the expected changes would be relatively small, whereas a 4.9-degree increase could bring drastic impacts, some of which may be unforeseen.

Carbon dioxide levels in the atmosphere have risen by 31 percent since preindustrial times, from 280 parts per million by volume (ppmv) to over 370 ppmv today. Other human activities, such as emissions of sulfate and soot particles and the development of urban areas, have significant but more localized climate impacts. Such activities may enhance or mask the larger-scale warming from greenhouse gases, but not offset it, according to the authors.

If societies could successfully cut emissions and stabilize carbon dioxide levels in the atmosphere, temperatures would still increase by an estimated ...