VOLCANIC ACTIVITY

Volcanic activity ranges from emission of gases, non-explosive lava emissions to extremely violent explosive bursts that may last many hours. The types of eruptions determine the relative volumes and types of volcaniclastic material and lava flows, consequently the shapes and sizes of volcanoes.A volcanic event occurs when there is a sudden or continuing release of energy caused by near-surface or surface magma movement. The energy can be in the form of earthquakes, gas-emission at the surface, release of heat (geothermal activity), explosive release of gases (including steam with the interaction of magma and surface of ground water), and the non-explosive extrusion or intrusion of magma. An event could be non-destructive without release of solids or magmatic liquid, or if there is anything to destroy, could be destructive with voluminous lava flows or explosive activity. Destruction usually refers to the works of mankind (buildings, roads, agricultural land, etc.).

A volcanic event can include

(1) an eruptive pulse (essentially an explosion with an eruption plume, but also non-explosive surges of lava. A pulse may last a few seconds to minutes, a.Calbuco volcano

(2) an eruptive phase that may last a few hours to days and consist of numerous eruptive pulses that may alternate between explosions and lava surges

b.Augustine Volcano

(3) a single eruption or eruptive episode, composed of several phases, that may last a few days, months or years (Fisher and Schmincke, 1984). Paricutin, Mexico was in eruption for nine years. Stromboli, Italy has been in eruption for over 2000 years.

c.Mount Etna