topics: |  science | geography | horrible | humour | volcano | juvenile

The book mentions the Grimsvoetn volcano in Northern Ireland, whose
eruption in 2011 was responsible for the shutting down of flights all over
Europe, though it was not as severe as the 2010 Eyjafjallajökull eruption.
The latter even was noticed even by many chess buffs when Vishwanathan
Anand almost missed the opening day 
of his world championship match against Topalov.   

Here is Ganeri on the Grimsvoetn: 
Iceland - 1996: the Grimsvoetn volcano erupted under 760 m of ice in the
Vatnajökull ice-cap.  Underneath, the magma chamber (molten rock) melted
ice at 6K tons per second, and after three weeks, this water broke through
the melted ice in a flood at 55,000 tons/sec leaving fields of house-sized
icebergs on its wake to the sea.  p.69

[see more about magma chambers on p.31]


	Part of the Horrible Geography series, this is 
	written in a humourous vein...

Strongly recommended for readers, young and old!!

'Volcanic Explosivity Index (VEI) : 1 to 8

The biggest volcanoes ever were of VEI=8.  The biggest one known was the 
"Toba super eruption" -- this happened about 75,000 years ago. 
It is thought that the earth was chilled for nearly a decade, and weather
didn't return to normal for almost a millenium. 

The human species (or close hominid cousins) are thought to be 120,000
years old, and at the time, the first humans had just emigrated out of
Africa.

Language, if it existed, was very new and it is a matter of deep scientific
interest to know whether they would have been able to communicate about
such events.  Quite likely, this would have been an "indescribable" event
for them, with supernatural portents!!

Biggest volcanoes ever

Toba, Sumatra, 75,000 BC - 8 - 2,800 km³ ash spread all over the world
		and caused frozen weather for years.
Tambora Indonesia, 1815 - 7
Taupo, NZ, 130 AD?  - 7
Novarupta, Alaska, 1912 - 6 (21 km³ ash)
Krakatoa Indonesia 1883 - 6 heard from Australia, 4,800 kmm away)

The Toba super-event

The Toba eruption is the most recent such supervolcanic eruption, and 
and is the focus of intense worldwide study.  One theory suggests that the 
living conditions for hominids on the planet was affected severely, with 
and that the population may have gone down to several tens of thousands. 

There is evidence from the DNA diversity that suggests that modern humans
have passed through at least one "genetic bottleneck", in which the
population diversity was  drastically reduced. 

Some people relate this to the Toba supervolcanic eruption.  

One of the areas that is being studied intensively for possible evidence on
this matter is the anthropological site at Jwalapuram, in
Andhra Pradesh, where mining has exposed a very large area of many hectares
down to the volcanic deposition period.


	Anthropological site at Jwalapuram.   From Petraglia etal, 2007. 
	[toba.arch.ox.ac.uk/pub_files/Clarkson2009Antiquity.pdf|pdf]

Here the archaeologists have discovered a 2.5 m layer of ash, and all through
it, and above and below, there are evidence of stone tools being used by the
humans of that period. 

It is not known what hominid species it was that lived in Jwalapuram - 
no fossil remains have been found so far. 

But here is why this site may be of interest in deciphering the effect of the
Toba super-event:

	When Toba Volcano in Indonesia blew its top 74,000 years ago--the
	largest known volcanic eruption--it caused a "volcanic winter" and
	may have decimated human populations worldwide. So few early human
	foragers survived the event that it caused genetic bottleneck that
	researchers claim is still detectable in our DNA today. In addition
	to affecting climate, it blanketed the Indian subcontinent in four to
	six inches of ash. But new finds in south India's Jwalapuram Valley
	suggest that humans there endured. In deposits above and below the
	ash layer, archaeologists found similar sets of stone tools,
	suggesting that people there survived the massive catastrophe with
	their culture intact, despite being relatively close to the source of
	the devastation.
		 Samir S. Patel, Archaeology Magazine, 2008

This also seems to imply that modern humans may have occupied South Asia
thousands of years earlier than previously thought.