One of the greatest and most immediate dangers presented by eruptions of volcanoes is lava.The temperature of lava ranges from 600 to 1200 degrees centigrade, a high temperature moving stream of melted rock, that is emitted during an eruption. Moving from the crater downhill at a significant speed, covering and burning down everything on its way. The speed at which the lava moves depends on its composition, how viscous it is, and how steep the slope is, the speed and amount at which it erupts. Its speed can reach thirty kilometers per hour, however a more common speed is around one kilometer per hour. Such speed gives people sufficient time to escape the flow. The flow can reach dozens of kilometers from the crater. The dangers of lava being erupted by under-ice volcanoes have to do with creation of lahars – flows of mud, which are far-reaching and destructive, it can cause the increase of the water-levels, consequently creating floods. If lava flows across water, it causes the water to boil and spatter explosively around a large area, lava produces large amounts of methane, which can move underground and later cause explosions. Most casualties caused by lava usually are not the result of the flow itself but rather of the explosions of lava interacting with water, the lahars and the toxic gases emitted either by the volcano itself or later on, from the lava. .
A specific characteristic of the damage caused by lava is that it drastically changes the landscape. Unlike after other natural disasters, the land after the volcano eruption usually can't be used by people. .
The above report offers abundant data upon recent volcano eruptions. The scientists from the USGS observe the emissions of gas in the United States,observing about seventy active volcanoes. The long-term effects that volcano eruptions have on the environment mainly have to do with the number of gases and ash that is emitted into the atmosphere.
