Large- and Super- volcanoes. Local and global Effects & Hazards

[madbadgalaxyman]

Here is a good paper by S. Self in the 2006 Philosophical Transactions of the Royal Society, dealing with the frequency & the nature & the size of the Effects (local and global) and Hazards caused by the very largest volcanic eruptions.

It is extremely readable, and avoids unnecessary geological jargon:
178784

[Shiraz]

thanks Robert - very interesting read. Seems like something will get us sometime in the future.
I guess that, since there is stuff all we could do to modify a volcanic eruption, the best approach is to be aware, but ignore until there is a definite threat. This is unlike some of the other threats like meteor impact or food crop failure, where we may be able to do something to head off the problem.

[madbadgalaxyman]

Gday, Ray,

There have been a number of studies of very large magma reservoirs in those places where there was previously a super-eruption , in order to try to figure out how and on what time-scale these vast magma bodies will finally make it to the surface..... and then "all hell breaks loose".

The two biggest eruptions in the last 5000 years are ::
- Lake Taupo (in N.Z.) between 180 and 200 AD
- Mount Tambora, in 1815, which lead to the famous 1816 "Year without a summer" in the Northern Hemisphere.

At Lake Taupo, the actual Volcanic Vents are on the bottom of the lake, which is a caldera that formed when the land slumped due to so much magma being extruded from underneath it.
(the caldera formed in the supergiant 26,500 y.b.p. Taupo eruption)
It is impressive to stand near Lake Taupo and to contemplate the fact that hundreds of cubic kilometers of magma might be making their way to the surface, right underneath your feet!!

Mount Tambora, on the Indonesian Island of Sumbawa, is a most impressive sight ::
2850 meters tall, with the 1815 eruption taking >=1200 meters off the previous height of the mountain. The caldera/crater at the top of the mountain is 7 kilometers across!!

Best regards,
Robert

Added in edit:
It has been suggested in the geological literature that the only eruption during the last 100,000 years that was big enough to cause Long Term and/or Severe disruption to the global climate was that of Toba (Lake Toba) in Sumatra, some 74000 years ago, though there are ongoing scientific controversies surrounding this assertion.

However, even the enormous volumes of magma and volcanic ejecta that were emitted by the Toba eruption (some 2800 cubic kilometers) pale in comparison to the volumes of Basalt lava which flowed out in series of eruptions that lead to the Deccan Traps and the Siberian Traps;
these two sequences of eruptions are probably the best candidates for volcanic phenomena that caused severe and long-term global climatic change, as over a million cubic kilometers of volcanic rocks can be extruded in a single related series of volcanic eruptions.
(just 'google' on "Flood Basalts")
(( see also:
http://www.le.ac.uk/gl/ads/SiberianTraps/Index.html for excellent info on the Siberian Traps ))

For instance, the basaltic eruptions leading to the Siberian traps have been implicated as a serious suspect for causing the Permian-Triassic mass extinction.