Explosive Eruptions Types
Explosive Eruptions Types : Explosive eruptions involve the rapid expansion of gas causing the surrounding rock or magma to fragment explosively. There are 3 types of explosive eruptions: (1) Magmatic Eruptions: Explosive magmatic eruptions occur when dissolved gases in a rising magma expand to form gas bubbles which then burst as the magma nears the Earth's surface, leading to explosive fragmentation of the magma. The bigger fragments are ejected (balistically) like cannonballs while the smaller fragments are transported vertically by the expanding hot gas into the atmosphere to form a vertical eruption column. The products of an explosive magmatic eruption include pyroclastic fall, flow and surge deposits. In 1979, the eruption of the Soufriere volcano of St. Vincent developed from a phreatomagmatic stage into an explosive magmatic stage. Several magmatic explosions have occurred during the ongoing eruption of the Soufriere Hills in Montserrat. (2) Phreatomagmatic Eruptions: Explosive phreatomagmatic eruptions occur when magma comes into contact with water causing the water to flash to steam. The expanding steam disrupts not only the pre-existing solid rock but also the magma itself so that the fragments thrown out are a mixture of broken-up old rocks and new rocks. The products of a phreatomagmatic eruption include pyroclastic fall, flow and surge deposits. The 1979 eruption of the Soufriere of St. Vincent began as a phreatomagmatic eruption and this is also the predominant eruption style of the Kick 'em Jenny submarine volcano. (3) Phreatic Eruptions: Phreatic eruptions occur when confined sub-surface geothermal waters are heated to temperatures above their boiling point and flash from water to steam. The resulting volume expansion and energy release drives the phreatic eruption. There is no direct involvement of magma in this style of eruption. These eruptions may eject steam, hot water, hot mud and/or hot and cold rock. In some cases the mud and water ejected may be acidic. In the Eastern Caribbean there have been numerous phreatic eruptions. The 1880 and 1997 eruptions in the Valley of Desolation in Dominica are examples of phreatic eruptions
No records Found