Glaciers on volcanoes could serve as early-warning systems

Mapping glaciers was once a difficult and arduous job. So was monitoring volcanoes for the grumblings and rumblings that might herald an eruption. In recent decades, the old methods of hiking boots and mountaineering gear have been joined by satellites and remote sensing, making things both easier and safer.But looking from afar has its drawbacks too. If a volcano is high enough to sport glaciers on its flanks (and many are), then the thick layer of ice can make it harder, or impossible, to get accurate temperature readings from the rock beneath.