This module will give you an insight into the physical dynamics and ecological interactions within glacial systems. We begin with the concept of mass and surface energy balance, determining when and where snow and ice melt may occur. This determines how water flows through a glacier and introduces the concept of hydrological regime. We then study the implications that this has for glacial dynamics and the legacy of past glacial systems in the environment. Where ice sheets and glaciers overlie active volcanic systems there is currently very little understanding of how the two forces interact - does volcanic activity control glacier behaviour or is it the other way round? We introduce the concept of studying glaciers as ecosystems, rather than just physical systems in the landscape, and discuss recent advances in glacier hydrochemistry in the context of climatic change.