WE were driving to London the other day, and anyone that has done that will have noted the spectacular road cuttings where the A30 meets the M5 at Exeter. It made me think that although we hear a lot about climate change, the bit of rock we now called Britain has had a remarkable series of climate variations over its history, some caused by our geographic position, some by the earth’s climate and, more recently, some by the impact of man.

The oldest rocks in Britain are in north-west Scotland, called the Lewisian gneiss (pronounced “nice”) which are almost three billion years old. Which is very impressive as we are a small island and we have rocks that are very recent as well, and pretty much most ages in between.

There are two red sandstone deposits in Britain, one formed about 400-350 million years old and the younger one being about 250-200 million years old. Being imaginative, the geologists call these the Old Red Sandstone and... wait for it... the New Red Sandstone. The Old Red was deposited in seas when Britain was just below the Equator and the New Red was when we were north of the Equator, in arid, hot desert conditions similar to the Sahara today. The New Red Sandstones tend to be brighter in colour and the redness is due to iron in the rocks that has oxidised.

Contrast that with weather in Britain in the last Ice Age, when early humans were evolving. There were actually four main glacial episodes with warm inter-glacial periods, when African animals were found in Britain. At its peak, much of Britain was covered, with ice in Scotland being over two kilometres thick. What wasn’t covered with ice was enduring permafrost, so not a great place to be. One of the direct impacts was the flooded ria valleys of Cornwall, caused as the north of Britain sunk under the weight of ice and then rose again as it melted, causing Cornwall to sink – and we are still sinking, at a rate of 1mm a year. All that due to climate variations.