The Cambridge Philosophical Society has its roots in the Earth Sciences, with all three of our founders (Edward Clarke, Adam Sedgwick and John Stevens Henslow) being engaged in geology at the University of Cambridge. Professor Marian Holness FRS in the Department of Earth Sciences at the University of Cambridge and Fellow at Trinity College Cambridge explores the geological and social history under our feet with some surprising finds.

The cobbled area outside Trinity College Great Gate is a useful area to park lorries making deliveries to the college, and also commonly hosts groups of tourists admiring the Gate and the statues above it. What is less recognised is the enormous scientific and historical interest of the cobbles themselves. Even a cursory glance from a non-specialist shows that there is a huge range of colours in the cobbles and that they are clearly natural materials with no evidence of them being cut into shape. A closer look tells us that there are many different rock types, most of which are not found anywhere near Cambridge with the source of a couple of types that can be confidently placed in southern Norway. These cobbles are most likely to have been laid in the sixteenth century, re-used from an older road down to the river - the makers of that road collected the cobbles from nearby fields, deposited there by glaciers during the greatest Ice Age almost half a million years ago. That we can see Norwegian rocks tells us that this huge ice sheet must have travelled from Scandinavia across the North Sea, ending up in East Anglia.

Video courtesy of Trinity College Cambridge.

Photo: Not all that glitters is gold: a larvikite cobble from Norway, with its characteristic iridescent grains of feldspar.