Presentation on theme: "“Supervolcanoes” and super eruptions Chapter 11 (pages 265-289) Presentation based on Miller and Wark, 2008, Elements, Vol 4, Issue 1, pages 11-16."— Presentation transcript:
“Supervolcanoes” and super eruptions Chapter 11 (pages ) Presentation based on Miller and Wark, 2008, Elements, Vol 4, Issue 1, pages 11-16
What makes an eruption “super?” The term “Supervolcano” was introduced by BBC/Discovery Channel in 1995 “supereruptions:” – eject magma with a mass greater than 1015 kg, equivalent to a volume greater than 450 km 3 – imply relatively short-term, and explosive events as opposed to fluid lava eruptions (think the current eruption of Kilauea Vs. Yellowstone Caldera forming eruption) – explosive eruptions of this magnitude have a volcanic explosivity index (VEI) of 8 or above and produce > 1000 km 3 of fragmental deposits A “supervolcano” can be defined as a volcano that has produced at least one explosive supereruption
Volcanic Explosivity Index or VEI VEIDescription Plume Height VolumeClassification How often Example 0non-explosive< 100 m1000s m 3 HawaiiandailyKilauea 1gentle m 10,000s m 3 Haw/StromboliandailyStromboli 2explosive1-5 km 1,000,000s m 3 Strom/Vulcanianweekly Galeras, severe3-15 km 10,000,000 s m 3 VulcanianyearlyRuiz, cataclysmic10-25 km 100,000,00 0s m 3 Vulc/Plinian 10's of years Galunggung, paroxysmal>25 km1 km 3 Plinian 100's of years St. Helens, colossal>25 km10s km 3 Plin/Ultra-Plinian 100's of years Krakatau, super-colossal>25 km100s km 3 Ultra-Plinian 1000's of years Tambora, mega-colossal>25 km1,000s km 3 Ultra-Plinian 10,000's of years Yellowstone, 2 Ma
Figure modified from Miller and Wark, Elements, Vol 4, Issue 1, page 12 Cubes represent relative volumes of ejected material
Effects of Toba supereruption 74,000 years ago Lake Toba at the site of Toba caldera, Sumatra: 100 Km long, 40 Km wide Figure modified from Miller and Wark, Elements, Vol 4, Issue 1, page 13
Supereruptions require: ENORMOUS volume of highly viscous magma (silica content >60%) accumulating in shallow magma chambers, which are part of even bigger magma reservoirs High volatile content (mostly water vapor) Thick, relatively low-density crust, common in continents or old island arcs help to create such HUGE magma reservoirs
High viscosity prevents the expanding bubbles from escaping Pressure builds up Figure modified from Miller and Wark, Elements, Vol 4, Issue 1, page 14
Explosive eruptions can happen if (when?): The magma body becomes partially solid and the volatiles are forced into the remaining liquid, making the liquid saturated in gas Fresh batch of hot magma intrudes in the magma chamber The gas-rich liquid magma escapes from the semi-solid crystal mush and is stored beneath the roof of the magma chamber, and, earthquakes and faulting fracture a magma chamber and/or “shakes up” the magma chamber
Supereruptions: “The ultimate geologic hazard” History Channel mega disaster: Yellowstone part I 1) Can the magma/lava shown in the documentary actually cause a super eruption? 2)How far below the surface is the magma chamber under Yellowstone? 3)List the potential warning signs expected before an eruption at Yellowstone 4)List the timings of the last three supereruption events at Yellowstone
History Channel mega disaster: Yellowstone part II 1) How long did the last Yellowstone eruption continue before the caldera formation? 2)How much ash was released in the last Yellowstone eruption? 3)List the effects of the ash cloud from the last Yellowstone eruption 4)What is the direction of the hot-spot trail ending at Yellowstone? How long ago did it begin? 5)How deep below the surface is the SOURCE of the magma chamber under Yellowstone?
History Channel mega disaster: Yellowstone part III 1) How did the animals die during one of the earlier supereruptions? What was the evidence behind that conclusion? 2)What happens when animals breath in volcanic ash for extended periods of time? 3)What were some of the impacts of the Toba eruption? 4)How do we know about the climate impacts of Toba eruption? How much did the global temperature drop?
History Channel mega disaster: Yellowstone part IV 1)How is the Yellowstone Volcano being monitored today? 2)What is a resurgent dome? How did the two resurgent domes form in the Yellowstone caldera? 3)How much magma is thought to be in the reservoir below Yellowstone? 4)What is currently happening at the Norris Geyser basin that might be cause for concern?
History Channel mega disaster: Yellowstone part V 1)Describe the safety measures that should be taken in the event of a future eruption at Yellowstone 2)Describe the progressive stages of a future Yellowstone eruption as predicted in the documentary 3)How far are the pyroclastic flows expected to reach? 4)How might the ash from the eruption cause global famine?