Snowball Earth ? Cool, Baby !

Anyone reading my first post in this blog will know that there have been four Great Ice Ages with varying amounts of evidence to support their existence. I was reading the Daily Mail yesterday and, to my great surprise, found an article about scientists who've been researching various deposits which confirm the theory of the Cryogenic Era. They were from St Andrew's University and had been researching ancient Irish rocks. According to the journalist, the theory was first 'coined in 1992' (sic) to explain the existence of massive glaciers at sea-level in the equatorial regions of that period. Also according to the journalist, the period lasted for about 10 million years. They are publishing findings which appear to give more detailed support to the theory.

The article was fairly short and it would appear that, as usual, a journalist has been given details on a topic they know little about, an article was written and then, thereafter, sub-edited down to fit the space available. In the process inaccuracies have crept in. I may be wrong on this but I wonder if the journalist was given a reference to the coining of the name of the epoch by Kirschvink (C.I.T) in the 1990s rather than the actual concept which was bouncing around a lot earlier.

Actually, the first Great Ice Age was thought to have been a Snowball Earth as there is some evidence which is replicated in the geological record during the period we now refer to as the Cryogenic period. That is a topic for another post.

I had to smile as I read the article. I first came across the concept/theory of the Snowball Earth in the 1960s as I studied Geology and Geography. There was quite a fair amount of discussion about it at the time. One thing was obvious though - the 10 million years mentioned above simply doesn't cut it for the length of time the Snowball Earth existed. As a matter of interest, this period and the whole issue of ice ages is dealt with in his usual superb inimitable style by Bill Bryson in his book "A Short History Of Nearly Everything". Well worth reading in my opinion. It's also worth mentioning that the theory is not without its critics - which is as it should be; any theory worth its salt should be challenged to within an inch of its life as far as I am concerned. That, of course, is why I militate so strongly against the "conventional wisdom" - based on limited knowledge as far as I can see - nonsense and scaremongering being peddled as facts about global warming / climate change by the media, those with certain political or 'green' agendas plus a certain 'wannabe' US president ('I don't plan to run again'. Oh yeah ?).

There are two points which can be made categorically. There is no 'unanimity' of world scientists. There are many, many climatologists, geographers, geologists who do NOT agree - many extremely well-known if not actually pre-eminent in their fields. Secondly, the science is NOT settled. In fact, ALL of the respectable science across a range of disciplines tends to refute all of the claims. For example, in "An Inconvenient Truth", Al Gore is correct to point out a correlation between CO2 and global temperatures. However, close examination shows he is wrong in his claim of which causes which. The CO2 levels actually follow climate trends not cause them ! Sunspot activity also gives a much closer correlation than CO2 and is considerably more co-terminous, suggesting sunspot activity is much more likely to be the cause than CO2. The problem is that he is likely to be dead before he is discredited.

Anyway, enough of the polemics. Back to the ranch.

The Snowball Earth Theory suggests that the Earth was covered in ice from the Poles to the Equator, hundreds of metres thick over most of the Earth, thinnning to perhaps only tens of metres in the equatorial regions. Most interpretations of the theory suggest that, based on biological information, some areas of ocean must have remained unfrozen. There is also the suggestion that there were local 'hotspots', possibly volcanic in origin, which kept some places just warm enough. Another suggestion is that there may have been places where the ice froze but remained clear enough for sunlight to penetrate. That's not common in nature but it does happen. I also read somewhere that nunataks [jagged horn peaks protruding through the ice - as opposed to mass onslaughts by little women in black dresses] may have been places with daily thawing and nightly refreezing. All offer the niches that life could have clung on to.

Why did it happen ? No-one's sure. A drop in solar radiation is thought to be one of the main causes. However, it is likely that that had to be combined with a fall-off in the production of greenhouse gases. Equally, in some way, the earth was unable to hold on to those it had already. It should be noted that greenhouse gases are essential to sustain us. Without them the earth would be a lifeless ball of ice.

What's the evidence ? Well, on to one of my favourite bits. Palaeogeography. We know that the continents have been moving about through the Earth's history. We can track them by looking at the orientation of iron particles in volcanic rocks for one thing. The Earth is a giant magnet with a field that stretches from Pole to Pole. It reverses from time to time, at fairly regular intervals. Again, a topic for another blog. The iron particles tend to align themselves with the earth's magnetic field whilst still molten. When the magma or lava begins to set that's them fixed. From the rocks we analyse, we can date them and work out where they were at various points in time. One of the pieces of evidence for continental drift / plate tectonics.

At this time, the continents were mostly in the area of the Equator, forming a clustering which is called Rodinia. Where do they get the names ? Rodinia, Pangaea, Laurasia, Gwondanaland ......... The evidence - the usual sort of glacial debris, markings, erratics etc - is sufficiently widespread to make it extremely compelling evidence. However, there's more. One interesting piece of evidence relates to iron. In our air iron oxidises ("rusts" to you and me). That's down to oxygen. Deposits of iron in non-glacial periods are oxidised. During Ice Ages - it's not, because oxygen levels are so much lower. Deposits from the Cryogenian period are unoxidised. Conclusion - Great Ice Age.

How long did it last ? Well it's far more than the 10 million years mentioned in the Daily Mail. Best estimates are around 170 million years viz. from 750 - 580 million years ago. Some estimates suggest even further back - to about 880 million years ago. The devil, as they say, is in the detail.

Why did it end ? How could it possibly have ended is actually a better question. The Earth reflects sunlight in various ways (The Albedo Effect). A giant snowball, 40,000 km in circumference, is going to reflect virtually everything. There would have been a clear blue sky without clouds. Nothing could stop heat being radiated back out into space. In theory, once having achieved that state, the Earth should have remained as a giant snowball thereafter.

One suggestion is volcanic activity. Look back a decade or so to the volcano beneath the Vatnajokul glacier which erupted, melting hundreds and hundreds of metres of ice which eventually poured down into the Atlantic as water. Could volcanic heat have begun punching through the ice ? Could volcanic emissions of Carbon Dioxide have begun to reconstitute the greenhouse gas layer needed to retain solar energy ? Once melting began, was there some form of feedback cycle which maintained and increased the melting process ? It's possible that Milankovitch's 3 cycles coincided positively towards the end of this period to begin the earth's temperatures rising again. Quite possibly all of these factors conspired. No-one's sure but we may find out eventually I suppose.

Footnote :

British geologists of yore were fascinated by the various rocks we call erratics today. They postulated floods and various other mechanisms to account for their movement. A suggestion was even made about a mythical race of giants carrying them as I recall. However, it was the Swiss who knew the mechanism was ice. From then theories and knowledge about glaciation have advanced, not without set-backs it has to be said. Noteworthy was Louis Agassiz. He became one of the best-known protagonists of the theory of glaciation although neither really feted nor well-known until he went to the USA and became a professor. Unfortunately, he tended to see more signs of glaciation than he was able to prove. Seeing signs of glaciation in equatorial zones was a step too far. He fell from grace when he proclaimed that ice had once wiped out all life before divine intervention restored it. He was actually closer than he knew. Time to rehabilitate him ?