* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Volcanism 3
Document related concepts
• Dynamic types related to magma/water interactions • Dynamic types related to dissolved bubbles • Dynamic types related to domes growth and collapse • Dynamic types related to lava flows etc. • Complex edifices • Destruction of volcanic edifices a vent 0 10 km scale sea level Shield Volcano: Mauna Loa, HI b c d Cinder Cone: Dome: Sunset Crater, AZ Composite Volcano: Lassen Peak, CA Mt. Rainier, WA. Figure 4-2. Volcanic landforms associated with a central vent (all at same scale). Réunion island Réunion Island Piton des Neiges (3100 m) (extinct) Piton de la Fournaise (2600 m) (active) Lava flows and more lava flows… But note also the grey material at the bottom… Helicopter view, NW coast (btw, this cliff tends to collapse quite often on the road) Cones groupe in Réunion + flows Shield volcano • Mostly a pile of basaltic flows! • Strombolian & Hawaian Stratovolcanoes Figure 4-3. a. Illustrative cross section of a stratovolcano. After Macdonald (1972), Volcanoes. Prentice-Hall, Inc., Englewood Cliffs, N. J., 1-150. b. Deeply glaciated north wall of Mt. Rainier, WA, a stratovolcano, showing layers of pyroclastics and lava flows. © John Winter and Prentice Hall. Lava flows… (Here, in the caldera wall on the top of Mt Pelée) … and explosive phases And erosion. Shield volcanoes vs. stratovolcanoes Shield volcanoes • Basaltic • Intraplate (hotspot) • Relatively flat • Effusive (lava flows, strombolian cones) • Minor explosive events (phreatic) • Erosion and flank collapse Stratovolcanoes • Andesitic to dacitic • Subduction • Rather steep • Explosive (plinian/pelean) • Minor andesitic flows a • Erosion, lahars and flank collapse • Dynamic types related to magma/water interactions • Dynamic types related to dissolved bubbles • Dynamic types related to domes growth and collapse • Dynamic types related to lava flows etc. • Complex edifices • Destruction of volcanic edifices Erosion and rivers Successive valleys and valley fills (Réunion Isl.) Lahars « Normal » landslides Cilaos Major landslides? Major debris avalanches forming the populated plateaux… Successive avalanches in the core of the volcano Consolidated breccias Megabreccias (Well, Ok, not in Réunion isl…Sorry, did not find photos from there) Superposition of breccia and flows! .. And more breccias Evidence for successive events: Breccia cut by dykes .. How major? Piton de la Fournaise Rift zone = major sliding plane? Evolution by successive flank collapses? A new view on shield volcanoes: • A succession of lava flows, and erosion – Local erosion (lahar, valleys) – Local/big erosions (large landslides, big depressions) – Major landslides (flank collapse), might be associated with eruptions (as in MSH, but no hard evidence for that) Volcanic islands: Tropical paradises or heaps of rubble?