VOLCANOES and VOLCANIC ERUPTIONS

• A volcano is a vent or chimney that connects molten rock, known as magma, from within the surface of the Earth
• The Ring of Fire is a major volcanic vent formed by many volcanoes in the rim of the Pacific Ocean, characterized by earthquakes and volcanic eruptions
• Divergent boundaries are found at the Mid Ocean Ridge, while convergent boundaries are points of subduction
• The mantle spans about 2890km thick and is composed of dense malleable rocks
• Magma is semi-molten rocks that try to escape upward through the spaces between plates towards cooler areas on the crust
• Lava is formed when magma reaches the crust and flows over the surface, building layers until a volcano is formed
• A lahar is a volcanic landslide, volcanic dust consists of very fine particles less than 0.25 millimeters in diameter, and volcanic ash is about the size of a rice grain
• Volcanic bombs are large rock particles ejected during volcanic eruptions
• Parts of a volcano include magma, conduit, fumaroles, landslide, pyroclastic flow, lava dome, ash, eruption column, and vent
• Fissures are elongated fractures or cracks on the earth's crust from which lava erupts
• The flank is the side of a volcano, and the magma chamber is an underground compartment where magma is stored
• Strato Volcanoes, also known as composite volcanoes, are built up of alternating layers of rock particles and lava, with a violent eruption occurring first during formation
• Shield Volcanoes are produced by the accumulation of fluid basaltic lava and have a broad, slightly dome-shaped structure with quiet lava flow
• Parts of a Shield Volcano include summit caldera and central vent
• Cinder Cones are small volcanoes built primarily of pyroclastic material ejected from a single vent, forming from explosive eruptions
• Extinct volcanoes have no record of eruption and no magma supply. Dormant volcanoes show no eruption recorded in the past 10,000 years but have the potential to erupt. Active volcanoes exhibit volcanic activity within the last 10,000 years.
• Geothermal activity occurs when magma beneath the surface heats underground water
• Non-violent eruptions build up the volcano, while violent eruptions destroy it
• Hawaiian eruptions are the least violent type, with highly fluid lava flowing out several vents, creating shield volcanoes
• Strombolian eruptions are violent, with continuous ejection of magma and gas, resulting in the formation of volcanic bombs and cinder cones
• Vulcanian eruptions are violent, with thick, viscous magma flowing around the vent and solid lava and dust being ejected