Yesterday I was arguing that as ice sheets melted at the end of the last ice age, 12,000 years ago, they gradually subsided to reveal the peaks of mountains and hills, which emerged as an archipelago of islands in a sea of ice.
But that was what was happening at the top of the ice. Today I’d like to consider what was happening at the bottom of the ice, hundreds and even thousands of feet beneath the upper surface of the ice.
I’m supposing in this respect that the subsiding ice was generally a solid mass of ice from top to bottom. There are reasons for supposing that this was not always the case, but for now I will suppose that the ice formed huge, unbroken slabs.
I’m also supposing that the ice was melting from the bottom upwards rather than the top downwards. But whichever way the ice melted, I’m supposing that the meltwater always end up at the bottom of the ice sheet.And from here it ran away under the ice in sub-glacial streams. And these streams formed tunnels beneath the ice, which eventually emerged from under the ice into the open air.
In times of strong melting (summer?) these caves would have been flooded with meltwater. But in times of little melting (winter?) the caves would have had narrow streams of water flowing along them. In places they may have even been almost perfectly dry.
And the environment inside these ice caves would have been warmer than the environment on the upper surface of the ice, which would have been well below freezing point for much of the year.
And so a variety of different animals would have occupied the caves where they emerged into the outer air. Some animals might have hibernated inside the relatively warm and dry caves during winter. Others, like bats or bears, might have lived inside them all year round, only emerging to hunt or gather food. Some migratory fish, like salmon, might have used the glacial streams as safe breeding grounds.
And humans would have also occupied the caves at the edge of the ices sheets. And they would also have explored the tunnels extending many miles under the ice. They may even have been able to tunnel through from one meltwater catchment area into adjacent ones.
So while humans would have been able to travel across the upper surface of the ice, using skis and sleds, they would also have been able to travel long distances beneath the ice. And where surface meltwater streams descended through the ice, they would have been able to use these to ascend to the surface, or descend from the surface.
The system of natural caves and tunnels beneath the ice would have provided something like a London Underground system of transport, augmented here and there with artificial tunnels.
And if these tunnels formed important trade routes across the ice, it would have been a matter of great importance to keep the tunnels open. However, since the ice would have always been slowly subsiding, some of the natural tunnels beneath the ice would have been prone to become blocked with fallen ice. And it would have been necessary to remove the fallen ice, and prop up any ice that was likely to fall.
In many cases, timber might have sufficed to prop up the ice above. But where the ice was deeper, it may have been necessary to erect substantial stone structures. The stones could of course be carried along the subglacial network of tunnels. But in many cases it might have been much easier to slide stones across the upper surface of the ice, and lower them down to the caves below, by the simple expedient of heating them so that they melted the ice under them, and descended to where they were needed.
The bluestones of Stonehenge are believed to have come from Carn Menyn in Pembrokeshire in Wales, a distance of 230 km (140 miles). The elevation of Carn Menyn above sea level is 1200 feet, and the elevation of Stonehenge is 328 feet, and of the nearby Avebury stone circle 512 feet . If there had been a 900 foot deep ice sheet overlying the site of Stonehenge, the stones could have been dragged across the ice rink surface of the ice sheet, assembled in place on the surface, and then heated and dropped through the ice onto the exact positions required.
And so, by this account of Stonehenge, it was no sort of temple or astronomical observatory at all, but was much more akin to the Piccadilly Circus underground station in London. It had been erected (or rather lowered) to act as a support for an ice sheet above it. And the same was true of the nearby Avebury circle.
And I would dare suggest that this is what all the megalithic structures throughout Britain were really for: supporting overlying ice sheets. If they were not stone circles like Stonehenge and Avebury, then they were stone avenues which supported the ice above tunnels, sometimes for several miles, or single stone pillars or dolmens used in one important place or other beneath the ice. And they of course remained standing once the subsiding ice sheets had completely melted.
And instead of being a mere 5,000 or so years old, Stonehenge might be more like 100,000 years old, having been erected at the start of the last ice age, rather than at its end.
Perhaps the principal objection to this account is that it is at present believed that neither Stonehenge nor Avebury ever experienced any glaciation. It is at present believed that most of southern England lay outside the ice sheets which extended over much of northern England and Wales. But it appears to be the case that the presence of ice anywhere is only discovered if the ice has been moving, and transporting rocks from one place or other, or forming moraines and other structures on the surface of the ground below. But must all ice move in the manner of alpine glaciers? It seems perfectly plausible that ice above flat plains (and Stonehenge is situated on Salisbury Plain) could have remained almost entirely motionless as it gradually melted away, and so left no record of its presence in the form of moraines or errant rocks.
Or rather, the only record of its presence would now be found in the existence of megalithic structures all over England, and in many parts of Europe.