W4 Volcano by Ng

W4 Volcano by Ng - Volcanoes UGB222EB NATURAL HAZARDS...

Info iconThis preview shows pages 1–23. Sign up to view the full content.

View Full Document Right Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full DocumentRight Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: Volcanoes UGB222EB NATURAL HAZARDS 自然災害 Volcano The giant Encelade betrayed gods. Athena buried him under Mount Etna. His shaking was earthquake, his breathing caused volcano eruption. Vulcan`s forge , by Velazquez (1630AD) 90% of volcanism (vulcanism) associated with edges of tectonic plates “Ring of Fire” surrounding the Pacific Plate Most other volcanism occurs above hot spots >80% of magma extruded through volcanism takes place at the oceanic spreading centres Oceanic spreading centres: release magma to create 20km 3 of new oceanic crust each year Subduction zones: create tall and beautiful volcanic mountains at edges of the continents; account for 7-13% of all magma Transform faults have little or no associated volcanism igure 12.16 Historically active volcanoes(red triangles) and the Afar Triangle (shaded, center)- a so-called triple junction (or triple point), where three plates are pulling away from one another: the Arabian Plate, and the two parts of the African Plate (the Nubian and the Somalian) splitting along the East African Rift Zone. Viscosity Volatiles Volume Basalt: Low; pancake batter Rhyolite: High; think flows move and solidifiy to form flow fronts of 50-100m high Andesite: In between; dark to pale Viscosity of magma depends on chemical composition and hence internal arrangement of atoms and molecules Oxygen, silicon, aluminum Chemical bonds of oxygen and silicon atoms are strong. More silicon, higher viscosity Volcanic rock type Basalt Andesite Rhyolite Description Black to dark gray Medium to dark gray Light colour Volume at Earth’s surface 80% 10% 10% SiO 2 content 45-55% 55-65% 65-75% Temp of Magma 1000-1250 o C 800-1000 o C 600-900 o C Viscosity Low Medium-high High Water dissolved in magma 0.1-1 wt % 2-3 wt % 4-6 wt% Gas escape from magma Easy Less easy Difficult Eruptive style Peaceful Explosive More explosive 冰島式 夏威夷式 斯沖坡利式 伏爾坎寧式 皮連式 普林尼式 Water: the most abundant gas in many magmas is what mainly inspires volcanoes to violence Hot steam under pressure: high temperature The amount of water a magma can contain decreases dramatically as it rises to a level rock pressure is lower. CO 2 has much less influence on the explosive nature of an eruption Ejecta volume, in cubic miles Volume Volume of magma expelled in a single eruption has a bearing on degree of hazard....
View Full Document

Page1 / 72

W4 Volcano by Ng - Volcanoes UGB222EB NATURAL HAZARDS...

This preview shows document pages 1 - 23. Sign up to view the full document.

View Full Document Right Arrow Icon
Ask a homework question - tutors are online