• Question: How are Crevasses in mountains and glaciers formed? And are they bottomless?

    Asked by sharpie to Davie, Gemma, James P, James V, Nuala on 25 Jun 2012.
    • Photo: James Pope

      James Pope answered on 25 Jun 2012:

      Hi sharpie,

      Crevasses in mountains are either formed when the mountain forms as the land is deformed by the crashing of tectonic plates pushing the mountains upwards. Those that form later are caused by erosion of the mountain by water, either water in rivers or water frozen into glaciers. These gouge out the rock and wear it down to form crevasses.

      Glacier crevases are formed when the glacier speeds up and so cracks itself where another bit can’t flow as fast.

      Crevasses are not bottomless, they eventually hit some solid rock, but they maybe so deep they are effectively bottomless, you wouldn’t want to fall in to some of the deep ones!

    • Photo: Gemma Purser

      Gemma Purser answered on 25 Jun 2012:

      Crevasses form in glaciers where the ice can’t bend and mould quick enough over the rock underneath so that the ice cracks, like if you bent moulding clay the top bit breaks. Sometimes the cracks go all the way to the rock at the bottom and the ice falls off the glacier in an ice avalanche, some of these ice-crashes are so big that they show up on earthquake detecting seismometer equipment. Other times the crevasses close up again as the ice bends back – when this happens large things can get trapped in the ice such as rocks, mammoth and even people! It can be thousands of years before they melt back out. Better cross them carefully!

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