Skip to comments.Why (Super-Volcano) Toba Matters
Posted on 04/18/2007 3:15:14 PM PDT by blam
Why Toba Matters
What can a volcanic eruption that occurred almost 75,000 years ago teach us about today's world of air pollution, global warming, and climate change? Heaps, says Dr. Drew Shindell, a climatologist at NASA's Goddard Institute for Space Studies in New York. For starters, knowing what the massive upheaval of Indonesia's Toba supervolcano did to the planet's climate (it might have cooled global temperatures enough to kill vegetation for years on end and perhaps hasten an ice age) offers sobering insight into what pumping billions of tons of chemicals into the atmosphere as we're now doing could result in. In this interview, Shindell shares his thoughts on Toba's impact then and now.
Q: I want to ask you about the lessons Toba might have for us today, but first a few questions about Toba itself. You've modeled how the world's climate likely reacted to Toba's eruption 75,000 years ago. What did you find? What happened?
Drew Shindell: Well, we found it was such a powerful eruption that it really could send the planet's temperatures dropping quite rapidly and keep them there for quite awhile. This isn't a long time period relative to ice ages, but you can make the planet cold for many years. And when people are trying to survive based on growing crops, [such cooling] each year for many yearson the order of 10 years or sothat can have pretty damaging consequences.
Q: Some experts have said that Toba might have even triggered an ice age. Can supereruptions do that?
Shindell: Well, I don't think a supereruption could really trigger an ice age. But I think that if we were on the verge of falling into one anyway, a supereruption could certainly provide that little push to get us rolling down the hill into an ice age. It could bring one on a little bit earlier.
Q: Do you think that happened with Toba?
Shindell: It's hard to say. There are a lot of signs that it did make the Earth quite a bit colder, and that cooling period extended for a long time. Part of the uncertainty that remains is that [the climate] seems to have warmed [up again] about 1,000 years afterwards before really settling into the actual depths of the ice age. So it's unclear whether Toba really did push us in and then something else happened 1,000 years later, or whether the effects of Toba were to make it cooler but it was really a temporary thing, and then we went into the ice age that we would have gone into anyway.
Q: What causes the climate in such a case where an ice age develops to slow its runaway cooling, reverse, and ultimately return the planet to a warmer period?
Shindell: Well, climate cycles are really driven by changes in the alignment between the Earth and the sun, and these things change extremely slowly. There are a few different cycles having to do with the shape of the Earth's orbit and the tilt of its axis, but the cycles range from about 20,000 to 100,000 years [in length].
Clearly crops will fail for year after year after year, and the whole planet would probably plunge into a terrible famine.
As the amount of energy reaching the Earth changes at different times of year, different parts of the Earth will be exposed to a different amount of sunlight, depending on the orbital configuration. How much energy reaches the northern latitudes, where you have a lot of land area and can develop ice sheets, is really the key factor.
So you go into an ice age if you have a reduction in the amount of sunlight reaching these northern high latitudes around 60 degrees that's enough to allow snow to persist during the summer. If the snow stays throughout the summer, it piles up year after year after year and you develop an ice sheet, which is a strong amplifier of the cooling of the country there in the first place by reflecting a lot of sunlight.
Then you just plunge into an ice age. And you really have to wait until the temperatures warm up enoughagain from the change in the astronomical alignmentto start melting that ice and bring you out of an ice age.
Q: Experts say it's only a matter of time before another eruption of Toba's magnitude occurs. If such a supereruption were to occur today, how would its effects on the climate differ from those 75,000 years ago, given our globally warming world?
Shindell: Well, there would be a number of differences. There are a couple of main factors, in my opinion, that would each go in somewhat opposite directions. One is we have a lot of modern technology that we didn't have back then, 75,000 years ago, of course. If the climate is degraded and there's less energy from the sun reaching the surface so that it gets darker and crops can't grow, we have some ways to get around that. We have things like our own ability to generate power. In some ways this would make it a little bit easier for us to deal with the climate problems induced by a supereruption.
But in most other respects, I would expect that it would be even more devastating than it was back then, largely because there are just so many people on the planet now. If six billion people need to be fed, you really can't tolerate a vast disruption in our ability to grow crops. If so much ash and soot are thrown up into the air that sunlight can't reach the surface, clearly crops will fail for year after year after year, and the whole planet would probably plunge into a terrible famine. That's what we think happened after the eruption of Toba. And if you look at the genetic studies, it seems there was a huge wave of extinctions right around then. Probably that was a result of the same thingthe blocking of the sun by the eruption.
Q: And Toba was not even the biggest supereruption that's been recorded. If a really huge supereruption were to occur today, could the climate potentially change so drastically as to threaten us as a species, or threaten life on Earth?
Shindell: Well, Toba was extremely large, and it did wipe out a lot of species, it seems, 75,000 years ago. But several of the other mass extinction periods, genetic bottlenecks if you will, in Earth's history are related to the timing of very, very massive volcanism. One of the most famous is, of course, the extinction of the dinosaurs. There was also apparently a large asteroid impact, but it is clear that there was a huge episode of volcanism right around the exact same time. And there are other periods when mass extinctions across different boundaries occurred, and in a time where again these are linked to volcanism.
So in the past we have a lot of evidence that genetic bottlenecks, when large fractions of the species alive on Earth at the time were wiped out, are really correlated with volcanism. I would say that if another supereruption were to occur, it would definitely have the potential to wipe out vast numbers of species living on the Earth. And, of course, there will be; it's just a question of when. We really don't have any capability to predict these things. Fortunately, they seem fairly rare.
Q: What lessons might Toba have for us today then?
Shindell: Toba offers us a few lessons that I think are interesting in a time of global warming. What we're seeing now is that as we put a lot of greenhouse gases into the atmosphere, the climate is slowly changing. But what something like Toba tells us, or may be telling us, is that the Earth's climate has sensitivities where if you push it too far, it might not come back. The cooling after Toba, as I've said, seems to have lasted about a thousand years.
Is there a chance that well push things into a new state where they wont simply return to where they were before? I think yes.
To the best extent that we can understand it, even if you throw a lot of particles and ash and chemicals up into the atmosphere from a supereruption, they hang around for awhilein the case of a very large eruption like Pinatubo in the Philippines in 1991, about three years or so; in the case of a supereruption, maybe a decade or so. But they're going to fall out just by their weight. It's not really so much a function of how much is up there, but just how long it takes for them to settle down out of the atmosphere. So the fact that the cooling seems to have lasted for a thousand years really implies that there are thresholds that can be crossed. There are ways that you can push the Earth's climate, and it doesn't simply bounce back when you stop pushing.
Those are important lessons when we try to consider what we should do about global warming at the present. Is there a chance that we'll push things into a new state where they won't simply return to where they were before? I think yes, there is a pretty high probability of that happening.
Q: I think many people still tend to think of the climate as so huge and robust that it takes thousands of years to change radically. But that just isn't true, is it?
Shindell: No, it apparently really isn't true. And actually most scientists had the same point of view for a long time. It took us a very long time to obtain evidence, and awhile afterwards to really be convinced by the evidence, that in the past climate has varied quite rapidly, sometimes with large changes taking place over times as short as a decade or so.
We have evidence from ice cores, which have a record of what happened to past climate, from both Greenland and Antarctica. As techniques have improved to extract information from these, we can get higher and higher temporal resolution and really see that sometimes changes can happen extremely rapidly.
One of the most interesting things going on now is the dramatic increase in the melt area and the rate at which ice is melting in Greenland. One of the things that always comforted us a little bit was there was so much inertia in the ice sheets that we thought we really didn't have to worry about them all that much. It takes millions and millions of years to build up an ice sheet, and presumably it would take an extremely long time as well for them to break down.
But as we get more evidence about what's happened in the past, and as we see what's going on now, we're beginning to doubt that that's really true, meaning how quickly they can break down. It does take millions of years for snow to pile up to a depth of a couple of miles as in Greenland, but it seems that snow and ice sheets can fall apart much more quickly, which makes sense when you think about it. If something starts to melt and breaks up into pieces and they all slide out into the ocean, it's just gone really quickly. And we see that's what's happened in the past.
We have new measurements that seem to indicate that just during the last five years or so the rate at which water has been coming off of Greenland has approximately doubled. It says that these things are really sensitive, and, in fact, the time over which they can respond might be much, much less than we thought.
Q: Al Gore's new documentary, An Inconvenient Truth, shows quite dramatic images of the Greenland ice sheet melting. As a climate specialist, what's your take on the film? Have you seen it?
Shindell: I haven't actually seen the film, but I've seen Al Gore's presentation, and I've been told that it's basically the same material. I thought that the material in the presentation was very well done. It was pretty carefully chosen so as to convey, in my opinion, a pretty accurate picture of what the scientific community thinks. It's not the most extreme viewpoint on either side but kind of the general consensus of what's been going on.
There are, as you said, dramatic pictures of what's been going on in the Arcticthe sea ice retreat and the melting over Greenland. These are really what's happening. This is what the data shows. It's not really anybody's opinion; this is just what the new measurements are showing. Even five years ago, we wouldn't have believed a lot of this. But now that's what the satellites are seeing, aircraft are seeing, people on the ground. It's all quite consistent and rather alarming.
What the past tells us is that bad things can sometimes happen.
Q: What would you see needing to happen, climaticalogically speaking, for world leaders to realize what most scientists now realize and to take action? What would convince them, do you think?
Shindell: I'm not sure there's an easy answer to that question. It seems to me that world leaders in many countries have been fairly receptive to at least trying to take initial steps to deal with the problem. That hasn't been so much the case here in the United States.
But I think maybe one of the best analogies is the case of smoking. It was a difficult problem to deal with because the hazards induced by smoking were way off in the future, so people didn't really want to quit smoking. They didn't really feel that it was that imperative to do it right away, and there wasn't really that leadership from above. It eventually came about, partially through the courts, but partially through general popular opinion changing.
I think that's part of what might happen from something like Gore's film. As more and more people see this, and as more and more people realize what the problem is, even though it's far away in the future, what has to happen is the American public has to put pressure on the leadership, has to say "This is not going to be a problem within your elected term of office" (which is generally two to six years in our government) "but it is a problem for you because we, the people who are electing you, are saying it's a problem." That has to be the transition, and I think we're starting to see more of that.
Q: You see things as a climatologist on scales that a geologist doestens of thousands of years. Yet things, as you've said, can also happen very quickly. How do you get the point across to people that things can happen quickly, that, say, we could jump to a whole new steady state of climate?
Shindell: Well, I like to give examples from the past. There are periods where we have seen things shift pretty abruptly. I mentioned before that we have evidence from the ice cores, and what we see is there have been times when something dramatic happened and climate seemed to really flip within even a decade or so. So there's really a history of it.
I mean, if you just see something happen in a climate model, sure there's lots of uncertainties in the model, and how do you really know if you should trust what this model says? Even if every model in the world said "In 10 years something dramatic is going to happen," how would you really know whether to believe that when the models are mostly used for looking at what's happened in the recent past, which hasn't been as dramatic?
But when you see that the records from the past really show that this has happened before, then we know that what we humans are doing is kind of an unplanned, uncontrolled experiment where we are putting a lot of stuff in the atmosphere and pushing at the Earth's climate system in a funny way. And when you start doing that, what the past tells us is that bad things can sometimes happen.
Regardless, I'll be posting more on Toba as this thread progresses.
Shhh, don’t tell Algore about Mt. Erebus.
by Peter Tyson
What could we expect if a supereruption were to occur today?
The closest I've come to seeing a supereruption waswell, not very. It was July 1987, and I had just climbed to the summit of Semeru, an active volcano and the highest mountain on the Indonesian island of Java, when it suddenly erupted.
It was the closest because it's the only volcanic eruption I've ever witnessed, and at the same time it was about as far from a supereruptionin size, impact, sheer horror, you name itas one could imagine. Still, since it's all I've got to go on, I use that eruption in my mind to try to imagine a supereruption, a once-in-a-blue-moon explosion that dwarfs "run-of-the-mill" eruptions like that of Mount St. Helens or Krakatau.
Scaling up from smaller eruptions is all the experts can do, too, since no one in recorded history has ever seen a supereruption. (The last one, depending on whose definition of supereruption you use, was either 26,500 or 74,000 years ago.) "It's very difficult to forecast quite what would happen, because it would be of a scale we just have no experience of," says Stephen Sparks, a volcanologist at Bristol University in England.
Nevertheless, by studying deposits from earlier such cataclysms, experts like Sparks can make educated guesses about what would transpire if a supervolcano went off. And, as I learned, the eruption I saw resembles a supereruption like the detonation of a firecracker resembles a nuclear explosion.
When it will blow
Knowing when Semeru ("suh-MARE-oo") will erupt again is a piece of cake: it explodes about every 20 minutes, like clockwork. I had been watching this progression of blasts for days before I ascended the mountain, admiring the mushroom-shaped plume that rose above the peak's ashen slopes for a few minutes before its source was choked off.
No such luck with supervolcanoes. Supereruptions occur so infrequently that even with the best-studied supervolcanic hot spots, experts only know about two or three at most that have occurred there, which makes it hard to nail down frequency. Moreover, since any early humans who saw and survived the eruption of Taupo in New Zealand 26,500 years ago or Toba in Sumatra 74,000 years agothe most recent known megablastsdid not record any details, experts today have no idea what the precursor signals to a supereruption might be.
"Some of us think you wouldn't be able to miss the signs and that they'd probably go on for quite a long time beforehand," says Stephen Self, a volcanologist at the Open University in England. "Others doubt this. They think there might be cases where there could be a very short period of unrest before a big eruption."
Add to this uncertainty the fact that scientists are still trying to figure out where all the supervolcanoes are. The first authoritative list of these giants was published only in 2004, and though considered a good start, it's incomplete. "There are considerable numbers [of supervolcanoes] missing from the list," says Self. "It's not anybody's fault. We just don't know about them."
On Semeru, I was able to sit on top and enjoy the periodic eruption because the crater is actually a quarter mile away and a few hundred feet below the summit. Happily the wind carried the ash cloud to the south, away from me. And of the six or eight eruptions I observed while up there, the most intense coughed up rocks at most the size of basketballs, and these landed not far from the crater rim.
A supereruption would not only take out the summit but the entire mountain and much else besides. The caldera that underlies Yellowstone National Park"caldera" essentially means humongous crateris over 50 miles long and nearly 30 miles wide. You could fit four Manhattans placed end to end inside. The amount of magma, or molten rock, thrown out by its most recent supereruption 640,000 years ago was a staggering 240 cubic miles, with an ash volume two to three times that.
Probably something like a third of the United States would be more or less uninhabitable maybe for a few months, even a year or two.
The intensity of such convulsions matches the magnitude. In A.D. 79, Vesuvius belched out an astounding 100,000 cubic yards of magma per second over a 24-hour period. Yet this is chicken feed compared to supereruptions, which can emit volcanic debris at up to 100 million cubic yards per second. You might have thought such violence was reserved for astronomical events like supernovas and gamma-ray bursts, but noour own Earth can generate it.
All that erupted material wouldn't just fall nearby or waft harmlessly away like Semeru's ash clouds, either. If something the size of that 640,000-year-old Yellowstone eruption occurred under New York City, it would not only obliterate all five boroughs but bury what was left as well as large portions of Long Island, New Jersey, and Connecticut under half a mile of pyroclastic flow deposits (see diagram at right). Pyroclastic flows comprise all the heavy stuff that collapses out of an ash cloud, and in supereruptions they can travel up to 60 miles away at speeds of 100 yards per secondagain, unimaginable fury. (A report published on the Web site of the Geological Society of London, which is the best single source for the layman on supereruptions that I've seen, puts the danger succinctly: "No living beings caught by a pyroclastic flow survive.")
A planetary peril
The devastation would spread much farther than the surrounding region. A stone monument atop Semeru memorialized several people who had died there after breathing volcanic fumes. But a supereruption would kill millions. "If you're close enough to the eruptionand in a supereruption that can mean thousands of miles awayif you breathe in the ash in an unprotected way, you're breathing in tiny glass needles," says geologist Michael Rampino of New York University. "They cause the blood vessels in your lungs to pop. Water in your lungs combines with this volcanic ash, and essentially you drown in a kind of soup or cement of wet volcanic ash."
Even if you survived long enough for the ash to settle, you could still succumb to longer-term effects. A supereruption would smother many millions of square miles under an inch or more of ash. Less than an inch can disrupt most forms of agriculture, so a single supereruption could lead to the starvation of millions of people. (Wildlife and natural habitats, needless to say, would suffer just as grievously.) Ash would collapse roofs, poison water supplies, and clog machinery such as vehicle and aircraft engines, causing transportation to grind to a halt.
"It would be pretty dire," says Bristol University's Sparks, who chaired the working group that prepared the Geological Society of London report, referring to another Yellowstone supereruption. "Probably something like a third of the United States would be more or less uninhabitable maybe for a few months, even a year or two."
A big enough supereruptionthe biggest yet identified unloaded 1,200 cubic miles of volcanic debriscould even have a global impact, threatening everyone on Earth. Aerosols shot into the atmosphere could create a worldwide haze that blocks sunlight sufficiently to change the climate for several years, with potentially disastrous effects on global agricultural yields. (Some scientists think the Toba supereruption might have gone so far as to speed the planet's plunge into an ice agesee Why Toba Matters.) Refugees pouring into surrounding areas, disrupted satellite communications, reeling world financial marketsthe fallout could be "sufficiently severe," notes the Geological Society of London report, "to threaten the fabric of civilization."
Before you pack up and move to Mars, know that supereruptions do have one encouraging characteristic: they don't happen very often. "Something on the order of every 100,000 years," says Jake Lowenstern, head of the Yellowstone Volcano Observatory (which keeps a close eye out for any unrest there).
"We could merrily go on for another 10,000 or 20,000 years without anything of this size happening," Sparks says. "On the other hand, at some stage, assuming that humanity outlasts all its other problems, we will face one of these eruptions. They are inevitable. So I think they have to be taken seriously."
Sounds like a good idea. In the meantime, if you want to catch an eruptionand survive itgo and watch Semeru from a safe distance.
Can I tell him to mount Cerebus?
“IMO, comparing ‘Global Warming’ to the eruption of Toba is lunacy. “
No not really volcanic ash would spread all over the world and block out the sun which in turn would cause global cooling. Just like pulling an awning out over a house what happens it cools off under the awning.
What I doubt or would doubt is the validity of a super volcano happening or did one happen all they know is they think they are possible none have been recorded that I know of. Have you? Enough Said
by Stephen Oppenheimer
The Toba explosion 74,000 years ago and the genetic evidence
Perhaps more important than the precision of the dating, the connection between stone tools and Toba volcanic ash in Malaysia puts the first Indians and Pakistanis in the direct path of the greatest natural calamity to befall any humans, ever. The Toba explosion was that disaster, the biggest bang in 2 million years. Carried by the wind, the plume of ash from the volcano fanned out to the north-west and covered the whole of the Indian subcontinent. Even today, a metres-thick ash layer is found throughout the region, and is associated in two Indian locations with Middle and Upper Palaeolithic tools. An important prediction of this conjunction of tools and ash is that a deep and wide genetically sterile furrow would have split East from West; India would eventually recover by re-colonisation from either side. Such a furrow does exist in the genetic map of Asia.
In spite of the proximity of Toba to Perak, the Toba ash plume only grazed the Malay Peninsula. The human occupants of the Kota Tampan site were the unlucky ones others on the peninsula escaped. Some argue, on the basis of comparing skull morphologies, that the Semang aboriginal Negrito hunter-gatherers, who still live in the same part of the dense northern Malaysian rainforest, are descendants of people like Perak Man. The continuity of the Kota Tampan culture as argued by Zuraina Majid provides a link back to the 74,000-year-old tools in the Toba ash.
The Semang are perhaps the best known of the candidate remnants of the old beachcombers. Another relict group possibly left over from the beachcombers in Indo-China and the Malay Peninsula are the so-called Aboriginal Malays, who are physically intermediate between the Semang and Mongoloid populations.
For a film documentary, The Real Eve (Out of Eden in the UK), with with which Stephen Oppenheimer 's book is associated, Discovery Channel helped to fund a genetic survey of the aboriginal groups of the Malay Peninsula which I conducted in collaboration with English geneticist Martin Richards and some Malaysian scientists. This survey was part of a much larger on-going study of East Asian genetics.
The mtDNA results were very exciting: three-quarters of the Semang group (i.e. the Negrito types) have their own unique genetic M and N lines with very little admixture from elsewhere, which is consistent with the view that their ancestors may have arrived with the first beachcombers. Their two unique lines trace straight back to the M and N roots (the first two daughters of L3 outside Africa). Their M line is not shared with anyone else in Southeast Asia or East Asia (or anywhere else) and, although it has suffered loss of diversity through recent population decline, it retains sufficient diversity to indicate an approximate age of 60,000 years. Their other unique group on the N side comes from R, Ns genetic daughter. This lack of any specific connection with any other Eurasian population is consistent with the idea that after arriving here so long ago, they have remained genetically isolated in the jungles of the Malay Peninsula.
The colonisation of Australia over 60,000 years ago was part of the same Exodus
Some are still convinced that Australian aboriginals represent an earlier migration out of Africa than that which gave rise to Europeans, Asians, and Native Americans. Yet again our genetic trail tells us otherwise. Several studies of Australian maternal clans have shown that they all belong to our two unique non-African superclans, M and N, and large studies of Y chromosomes show that male Australian lines all belong to the same Out-of-Africa Adam clan as other non-Africans (M168). The same pattern is seen with genetic markers not exclusively transmitted through one parent. In other words, the combined genetic evidence strongly suggests Australians are also descendants of that same single out-of-Africa migration. The logic of this approach, combined with the archaeological dates, places the modern human arrival in the Malay Peninsula before 74,000 years ago and Australia around 65,000 years ago. It is also consistent with the date of exit from Africa predicted on beachcombing grounds.
My date estimates for the trek around the Indian Ocean en route from Africa suggest that the beachcombers could have taken as little as 10,000 years to eat their way down the coastline to Perak and roughly another 10,000 years to reach Australia. Such a time requirement is fulfilled by the difference between leaving Africa around 85,000 years ago and arriving in Australia 65,000 years ago. The former date is consistent with dates estimated for the African L3 cluster expansion using the molecular clock.
A genetic furrow in India resulting from the Toba explosion?
There is an abrupt genetic change to the north and east of India. These changes can be inferred even from physical appearance. In Nepal, Burma, and eastern India we come across the first Mongoloid East Asian faces. These populations generally speak East Asian languages, contrasting strongly with their neighbours who mostly speak Indo-Aryan or Dravidian languages. By the time we get to the east of Burma and to Tibet on the northern side of the Himalayas, the transition to East Asian appearance and ethnolinguistic traditions is complete, as is the rapid and complete change of the mitochondrial sub-clans of M and N. In Tibet, for instance, the ratio of M to N clans has changed from 1:5 to 3:1, and there is no convincing overlap of their sub-clans with India. Instead, Tibet shows 70 per cent of typical East and Southeast Asian M and N sub-clans, with the remainder consisting of as-yet unclassified M types of local origin. The north-eastern part of the Indian subcontinent therefore shows the clearest and deepest eastwest boundary. This boundary possibly reflects the deep genetic furrow scored through India by the ash-cloud of the Toba volcano 74,000 years ago.
To the south of the Indian peninsula, the main physical type generally changes towards darker-skinned, curly haired, round-eyed so-called Dravidian peoples. Comparisons of skull shape link the large Tamil population of South India with the Senoi, a Malay Peninsular aboriginal group intermediate between the Semang and Aboriginal Malays (see above).
M born in India, N possibly a little farther west in the Gulf M, who is nearly completely absent from West Eurasia, gives us many reasons to suspect that her birthplace is in India. M achieves her greatest diversity and antiquity in India. Nowhere elsem does she show such variety and such a high proportion of root and unique primary branch types. The eldest of her many daughters in India, M2, even dates to 73,000 years ago. Although the date for the M2 expansion is not precise, it might reflect a local recovery of the population after the extinction that followed the eruption of Toba 74,000 years ago. M2 is strongly represented in the Chenchu hunter-gatherer Australoid tribal populations of Andhra Pradesh, who have their own unique local M2 variants as well as having common ancestors with M2 types found in the rest of India. Overall, these are strong reasons for placing Ms birth in India rather than further west or even in Africa.
What is perhaps most interesting about the unique Indian flowerings of the M and R clans is a hint that they represent a local recovery from the Toba disaster which occurred 74,000 years ago, after the out-of-Africa trail began. A devastated India could have been re-colonised from the west by R types and from the east more by M types. Possible support for this picture comes from the recent study by Kivisild and colleagues of two tribal populations in the south-eastern state of Andhra Pradesh. One of these populations, the Australoid Chenchu hunter-gatherers, are almost entirely of the M clan and hold most of the major M branches characteristic of and unique to India. The other group, the non-Australoid Koyas, have a similarly rich assortment of Indian type M branches (60 per cent of all lines), but have 31 per cent uniquely Indian R types. The Chenchu and Koya tribal groups thus hold an ancient library of Indian M and R genetic lines which are ancestral to, and include, much of the maternal genetic diversity that is present in the rest of the Indian subcontinent. Neither of these two groups holds any West Eurasian N types. The presence of R types in the Koyas but not in the Australoid Chenchus might fit with some component of a recolonization from the Western side of the Indian subcontinent. As evidence of their ancient and independent development, and in spite of their clearly Indian genetic roots and locality, there were no shared maternal genetic types (i.e. no exact matches) between the two tribal groups
Super Volcano ping!
Blast From The Past
(Click then go to the site and click on ' launch interactive' to see all the known super-volcanoes)
"The most recent one (Taupo, in New Zealand) occurred 26,500 years ago. One from 74,000 years ago (Toba, in Indonesia) left behind a caldera, or giant crater, about the size of Rhode Island. The biggest one yet identified (La Garita, in Colorado) coughed out 1,200 cubic miles of volcanic materials. On this map, sample a selection of the aptly named, though thankfully extremely rare, natural cataclysms known as "supereruptions."Peter Tyson"
I've heard that it is 40,000 years late for the average time between previous eruptions.
"Wasnt the last one a couple hundred thousand years ago?""
640,000 years ago.
Chapter 5, Toba Volcano
Through the Bottleneck
Table of Contents to Chapter 5
5-1. A Most Peculiar Mammal: Homo sapiens
5-2. Genetic Bottleneck
5-3. Before the Bottleneck
5-3.1 Homo idaltu in Ethiopia, 160,000 years ago
5-3.2 Homo erectus (?) in Malaysia, 75,000 years ago
5-3.3 Homo neanderthalensis in the Middle East, 75,000 years ago
5-4. After the Bottleneck
5-4.1 Homo neanderthalensis in the Middle East, until 30,000 years ago
5-4.2 Homo erectus (Ngandong 6) on Java, Indonesia, until 25,000? years ago
5-4.3 Homo floresiensis on Flores island, Indonesia, until 12,000 years ago
5-5. Winner Takes All
Homo sapiens spreading worldwide
Supervolcanoes don’t have supervolcanic eruptions on a schedule, at the present location of Yellowstone Caldera there have only been three supervolcanic eruptions, which is hardly a dataset to derive a “schedule” from...
Yellowstone isn’t “overdue” in any conceivable sense.
There’s ample evidence of supervolcanic eruptions all over the world.
None have occured in recorded history, but the evidence is pretty obvious from ash deposits, etc.
A recent Science channel show demonstrated how volcanic eruptions took us out of a global "snowball earth" ice age. Another idiot and his 15 minutes of fame.
I stopped reading right there.
Obviously, this clown doesn't have enough brain cells to understand the difference between the most massive volcanic eruption that we know of, and human-induced CO2.
The difference is so mind-boggling dramatic that this person should be checked out by the white-coat meds --- soon.
I remember very well back in the early 70’s, the gov. and wacko’s telling us that using up all the fossel fuel (and it would be gone in 30 years) that we would soon be entering a new ice age.
And now, it's 'Global Warming' and some of the dry oil wells have 'refilled.'
Please FREEPMAIL me if you want on or off the
"Gods, Graves, Glyphs" PING list or GGG weekly digest
-- Archaeology/Anthropology/Ancient Cultures/Artifacts/Antiquities, etc.
Gods, Graves, Glyphs (alpha order)
It might well be true, but it isn't provable.
So, let's get this right, Toba caused global cooling by throwing off essentially pollutant gases. BUT climate cycles are driven by the earth's orbital variations.
So we must fight Global Warming! or GoreBaloney!
|GGG managers are SunkenCiv, StayAt HomeMother & Ernest_at_the_Beach|
Just updating the GGG info, not sending a general distribution.
Disclaimer: Opinions posted on Free Republic are those of the individual posters and do not necessarily represent the opinion of Free Republic or its management. All materials posted herein are protected by copyright law and the exemption for fair use of copyrighted works.