21-Feb Glacial Erratics & Drop Stones

21-Feb Glacial Erratics & Drop Stones

I have been collecting small rocks and stones that have been brought up from the seabed by the bottom trawl. Interestingly there is no consistency about them, there being many different colours and types of rock. John Mitchel our voyage leader, informs me that they are so varied because they have been ‘ice rafted’ from the Antarctic mainland. I learn that they are thus called Glacial Erratics - Glaciers apparently pick up the rocks as they slip slide down the mountain. When the iceberg calves off from the end of an ice tongue or ice shelf, it drifts out to sea and as it gradually melts from the bottom, the rocks that it had picked up on the trip down the mountain drop to the seabed. John pointed out an interesting larger rock our net picked up and one could clearly see heavy scoring where the iceberg or glacier had dragged it along a hard the bottom.

Large glacial erratic mysteriously appears in Doc Jenny’s bed in a black bag, Max is investigating further and starts a ‘Who Dun it’ documentary on it – watch this space.