although glacial ices are solid it actually flows like a river it's incredible to think that this much ice is constantly on the move I've been climbing up to see what drives the glacier and it's the phenomenal weight of this enormous ice pack over nine kilometers long and up to five hundred meters deep millions of tonnes of ice crammed into this valley built up from layer upon layer of snow this monumental river of ice is constantly being topped up by fresh snowfall and that keeps it flowing downhill it makes very slow progress but there is a way to see it move a time-lapse camera shows that brains surface ice travels at around 275 meters per year carving away the rock as it goes when you're here the only clues you see of the glaciers movement are crevasses deep gashes that split open the surface of the ice these open up at the top of the ice one of the reasons is that atop the ice is brittle and tough further down where it's being squeezed it's more plastic and soft glass the Glaceon removes the brittle part of the top breaks open and creates these these great crevasses when a crevasse has opened up in the ice melt water can gather in it and start hollowing its way down towards the bedrock here it carves out a hidden world of icy caverns deep within the glacier I'm going to try to abseil right into the heart of the glacier to see for myself how it moves I was amazing so this is it when the engine new as a glacier you can see just down here right where the ice meets the ground and this is where everything important happens I'm getting pretty wet here was a little melting water from the ice but it's that that helps the Glacia slide on its belly and one of the things that makes it so dynamic new God's Plains temperate mountain climate means the ice at the lower end of the glacier exists very close to melting points as well as the meltwater flowing beneath the ice which helps lubricate the glacier on its journey down the mountain there's meltwater within the ice itself seeping out of these walls and that melting water also makes this cave and other caves like it probably all around and I bet this cave wasn't here last year and it probably won't be here next it's transient it's part of the science that the glacier is dynamic and moving and changing all the time you