Changes in the Air
Some volcanoes erupt quietly; others violently shoot gas, steam and ash into the air. After a volcano erupts, gases are released into the atmosphere. These gases include water vapor as well as carbon dioxide, sulfur dioxide, hydrogen sulfide, carbon monoxide, hydrogen gas and methane. All of these gases can form acid rain in high concentrations. Incorporated in the mass of gases expelled from a volcano exist tiny rock particles called tephra. Tephra particles can adhere to gas particles and be carried for great distances according to the U.S. Geological Survey. The immediate effect of high concentrations of gas in the air result in closure of the airspace above and around the volcano to air traffic. Over time, upper level winds can carry volcanic gases around the world.Ash particles impede air traffic as well as create immense breathing difficulties for people living near an erupting volcano. After a volcano, these 2-mm or smaller ash particles fly through the air, coating everything near the volcano. Ash particles can form a layer just like snow but it's much harder to remove. Combined with water, the ash becomes a mud-like mass. The Federal Aviation Administration monitors volcano eruptions to prevent planes from traveling in areas with possible ash particles in the air due to the dangers of loss of visibility and possible engine failure. Ash particle clouds also rise into the atmosphere for transportation with the prevailing winds, making their existence dangerous to any aircraft flying in the vicinity.
Changes to the Landscape
Every volcano makes a change to the landscape of the earth after an eruption. Volcanoes build new earth with every eruption, spewing hot lava from deep inside the earth onto the much cooler surface. After a volcano erupts, the magma flows down the sides of the volcano, reaching a point where it cools enough to stop flowing. As the flow progresses, everything in the lava's path is consumed. Plants, animals, buildings, roads, and trees are burned completely. Lava flows cool over time and form new rock. Wind, rain, and water after lava flows with weathering to break down lava and turn it into soil. When a volcano expels high volumes of ash, this coats the surface of the land around a volcano. This creates a dangerous condition of unstable earth with a thick layer of ash coating the sides of mountains and hillsides. Lahars are violent mudslides that result of waterlogged ash rushing down the sides of a mountain. These dangerous mudslides carry ash, rock, and debris, obliterating everything in its path.
Changes to the Water
Rivers and streams near erupting volcanoes suffer the effects of ash, hot gases and lava. After a volcano erupts, the debris expelled by the volcano affects waterways in a number of ways. Streams and rivers form a very basic part of the hydrologic cycle to disperse water through a drainage basin toward the sea. Volcanoes disrupt this process by blocking stream and river bed flows, re-routing courses, and contaminating the water supply with dangerous gases and particles. Fine ash can be carried away easily by water, but it takes time to restore a waterway after an eruption.
Effects on Plants and Animals
Like humans, animals can survive with little permanent effect resulting from ash deposition--as long as the ash isn't too hot and doesn't cover their source of food. The greatest threat from a volcano comes from damage to the environment. Ash quickly contaminates water, a necessity for any animal. Without access to an untainted water supply, many wild animals move to safer areas. Fish are extremely susceptible to a change in water quality. Volcanic eruptions often result in complete kills in streams and rivers near volcanoes. Ash contaminates the water, and burned or dead trees don't provide enough shade along these rivers to keep water temperatures down. High sediment content in the water prevents proper feeding, movement and reproduction. Birds naturally have difficulty flying in areas with ash clouds. Hot gases are deadly to birds as well. Plants and trees suffer from the effects of heat generated by the eruption and deposition of ash and sediments. However, unburned trees recover and usually continue growing after ash is washed off the tree itself. According to the U.S. Geological Survey, the increased amount of erosion possible with ash and tephra depositions creates slower re-vegetation of any damaged areas. Tephra contains potassium and phosphorus that are valuable nutrients for rich, fertile soil. Weathering helps release these nutrients into the soil, creating the prime environment for renewed growth of native plants and trees.
