SCI - Lesson 2

• Mt. Pinatubo, one of the composite volcanoes that constitute the Luzon volcanic arc, erupted in June 1991. On June 15, the Philippine Institute of Volcanology and Seismology (PHIVOLCS) recorded a total of 19 eruptions on that day.
• Filipinos literally experienced a

  "day without a sun" when huge mushroom-shaped clouds disturbed the stratosphere up to 20 km high.

  Pyroclastic materials and volcanic mudflows (lahar) flowed down Pinatubo's gullies into rivers and heavy ashfalls blanketed the provinces of Zambales, Pampanga, and Tarlac.
• Volcanic process refers to the eruptive and non-eruptive activities that take place in a volcano.
• Intrusive igneous rocks are magma trapped beneath the surface that cools and solidifies into coarse-grained materials.
• Extrusive igneous rocks, on the other hand, are lava that were ejected from the volcano and flowed out through fractures onto Earth's surface.
• two types of volcanic eruptions based on their activity are explosive and effusive
• explosive eruptions which are characterized by gas-driven explosion that propels magma and tephra
• effusive eruptions feature the outpouring of lava without significant explosive eruption.
• Geologists classify volcanic eruptions according to three metatypes of eruption: magmatic, phreatomagmatic, and phreatic eruptions.
• Hawaiian - type of magmatic eruption named after the Kilauea volcano on the big island of Hawaii
• Strombolian - eruptions driven by the bursting of gas bubbles within the magma. When these gas bubbles accumulate, they produce large bubbles called gas slugs which can grow into size large enough to rise through the lava column.
• Vulcanian - named after the Italian island Vulcano, which is also believed to be the home to the Greek god of fire, Hephaestus (Vulcan for Romans). It is an explosive eruption that occurs when the pressure of entrapped gases in a relatively viscous magma becomes sufficient to blow off the overlying crust of solidified lava.
• Pelean - also called nuée ardente eruption, it occurs when a large quantity of gas, dust, ash, and lava fragments are blown out of a volcano's central crater.
• Plinian - considered the most explosive and powerful of all eruptions.
• Surtseyan - named after the island of Surtsey off the coast of Iceland. It is a kind of hydromagmatic eruption where magma interacts explosively with shallow groundwater or surface water.
• 5 types of magmatic explosions are hawaiian, strombolian, vulcanian, pelean, and plinian
• 3 types of phreatomagmatic eruptions are surtseyan, submarine, and subglacial
• Submarine - type of volcanic eruption that takes place beneath the surface of water.
• Subglacial Eruption - also called glaciovolcanism, which features the interaction between lava and ice often under a glacier. This type of eruption occurs at areas of high latitude and high altitude.
• phreatic eruptions, also called steam-blast eruptions, are those driven by explosive expanding steam resulting from cold ground or surface water coming into contact with hot rock or magma