The bottom of the seafloor shows us where ice used to flow. To pinpoint when the ice retreated, the geologists on board take samples of mud and sand from the seafloor. Using a weighted steel barrel lowered to the seafloor they bore their way through sand and mud. A catcher at the bottom of the barrel prevents the sediment from falling out when the corer is hoisted up.
The different layers of sediment help us identify episodes of ice retreat. If we come across shells or tiny plankton fossils in the sediment we can use them to date those episodes. So far we have taken more than 20 cores and and will take several more if the weather holds.