A few months ago I wrote about the significance of recent findings regarding the Toba super volcano in Indonesia (The Toba Super Eruption: A non-Flood Catastrophe – the Artifacts Say Yes). Briefly, I explained that the Toba volcano caldera produced the largest eruption in the past 100,000 years releasing an estimated 2800 cubic kilometers of ash into the atmosphere (for comparison, Mt. St. Helens released only 1 cubic kilometer of ash) which covered thousands of square miles. This catastrophic event had been hypothesized to have global climatic effects possibly even wiping out much of the human population in the northern hemisphere at the time. I reported before on studies of YTT (younger toba tuff) ash deposits in India which revealed the presence of human artifacts deposited below these YTT deposits providing very strong evidence that humans, possibly Neanderthals and/or modern humans, were indeed present in the region at the time of the eruption. Because that eruption has been dated to 74-80 thousand years ago it generated a lot of discussion in the literature about how widespread humans were prior to these epic event and what this event might have done to those populations. You can review more about these hypotheses and the challenges they present to young earth creationists in my prior post.
In the past week a new paper has been published in Proceedings of the National Academy of Science (Astronomically calibrated 40Ar/39Ar age for the Toba supereruption and global synchronization of late Quaternary records) which is open access and describes further efforts to pin down the date of the Toba super eruption. In that paper they calculated a date of 73.88 +/- 0.33 thousand years for the deposition of ash in Malaysia to the east of the Toba crater. The importance of this date is that before this the estimated dates of the explosion ranged from 70 to 80 thousand years ago. You might be asking, why is the date important? What could a few thousand years of variation matter? This might not sound like a big deal. It was already known from ice core data and other sources that the world experienced several hundred years of cooling around that time, but did this massive volcano cause that cooling or was the world already cooling when the volcano blew its top. Only very precise dating that is matched up across many points on earth can help to answer that question.
What do ice cores have to do with a volcanic eruption in Indonesia?
The Greenland ice cores are cores taken from the massive Greenland ice cap. One core taken in north Greenland reaches nearly two miles in-depth and at 2548 meter depth mark there is a large sulfate anomaly. Sulfates in the ice are indicative of fallout of the sulfur compounds that are released by volcanic eruptions. Only the largest eruptions release enough sulfates to be distributed around the globe in high enough concentrations that they would easily identified in the snow fall and eventually ice production in Greenland. Some recent volcanic explosions are recorded in these cores like Krakatoa which is found in the top few meters of the ice core. The critical features of the ice cores is that right after this sulfate spike at 2548 meters there is evidence (based on Oxygen isotopes) that the following several hundred years, as recorded in the ice, were much colder. There is a similar sulfate spike in the east Antarctica ice core (Svensson et al. 2012). Those sulfate spikes in the ice cores that are dated to 74 thousand years are very likely the result of the Toba super eruption and with a more precise date for the Toba explosion it is now possible to synchronize events at different places on the globe to this event. The hypothesis that the Toba event caused global cooling becomes more likely and can be further tested by examining other places where precise dates can be gained.
As an aside, in the Antarctica ice core ash/sulfates from the Krakatoa volcanic explosion in 1883 are found only 13 meters deep in the 3000 meter deep ice core. The Tapau volcanic explosion of year 186 is found 103 meters deep in the core (See this paper for data from other volcanoes from the past 4100 years: A 4100-year record of explosive volcanism from an east Antarctica Ice Core). What we see in the ice cores from both poles is that human recorded events from the past 4000 years are all found recorded in the ice cores in just the top 200 meters of what are 2000+ meter cores. The implications of this should be clear for young earth creationism and so I won’t pursue this any further here.
The other notable factoid I gained from the Storey et al. 2012 paper in PNAS that further backs up my observations in my previous post is that not only are their human artifacts in India under the Toba ash but artifacts (stone tools) have also been found in Malaysia under the Toba ash. This extends the geographical region that modern humans or Neanderthals are known to have populated immediately before this super eruption occurred. Did they survive through this event or where these populations destroyed? That is a question that has generated considerable interest and is the reason that in the coming years I am sure that we will learn many more details about these populations as new sites are dug up and examined.
Storey, M., R.G. Roberts, and M. saidein. 2012. Astronomically calibrated 40Ar/39Ar age for the Toba supereruption and global synchronization of late Quaternary records. PNAS 2012 ; published ahead of print October 29, 2012,doi:10.1073/pnas.1208178109
Petraglia, M.P., Korisettar, R., Boivin, N., Clarkson, C., Ditchfield, P., Jones, S., Koshy, J., Lahr, M., Oppenheimer, C., Pyle, D., Roberts, R., Schwenninger, J.L., Arnold, L., and White, K., 2007, Middle paleolithic assemblages from the Indian subcontinent before and after the Toba super-eruption, Science, 317, 114-116.