Plinian eruptions are characterized by both the extrusion of high-viscosity lava flows and the violent explosion of released gases that blast huge quantities of ash, cinders, bombs, and blocks skyward. Less violent Hawaiian and Strombolian-type eruptions are associated with fissures that often produce a line of fire fountains. These geyserlike fountains of lava may shoot several hundred feet into the air and form a nearly continuous curtain of fire. The basalt lava is extremely fluid and flows down the mountain sides in torrents. When these streams reach the sea, they form pillow lavas, lobes of stacked lava that resemble a pile of pillows.
Volcanoes provide a wealth of natural resources.
Emissions of volcanic rock, gas, and steam are sources of important industrial materials and chemicals, such as pumice, boric acid, ammonia, and carbon dioxide. In Iceland most of the homes in Reykjav k are heated by hot water tapped from volcanic springs. Greenhouses heated in the same way can provide fresh vegetables and tropical fruits to this subarctic island. Geothermal steam is exploited as a source of energy for the production of electricity in Italy, New Zealand, the United States, Mexico, Japan, and Russia. The scientific study of volcanoes provides useful information on Earth processes.