towering cliff of ice hangs above Michele


Koppes. She is in a kayak, paddling. Suddenly, she hears a loud crack. A huge piece of ice breaks away from the cliff . It splashes into the cold lake, creating waves. T e waves rock the kayak, tossing it between jagged chunks of ice. Koppes keeps paddling. Aſt er all, this is what


she has come to see. Koppes is a glaciologist, a scientist who studies glaciers. Glaciers are huge masses of ice. T ey flow like rivers, but they move slowly. Glaciers form in places where snow never


completely melts. Instead, the snow builds up year aſt er year. Over time, the layers of snow squash the lower layers into ice. Yet a glacier is more than layers of ice. It’s


layers of ice that move. Koppes usually can’t see the ice move, but she can hear it. Bang! A thunderous noise stops Koppes. She


and her companions have pulled their kayaks onto a rocky shore. T ey pause to listen. Koppes knows this sound. It is the sound


of moving ice. When ice gets to be about 40 meters (130 feet) thick, its great weight forces it to slide forward. Glaciers don’t move quietly. T ey crack, rumble, and bang.


Ice and More Ice Glaciers form on every continent except Australia. Small glaciers are no bigger than two football fields. T e largest glaciers are the size of a continent. Altogether, glaciers cover ten percent of Earth’s land area. Some glaciers are sheets of ice. T ese ice


caps cover large areas of land. For example, Greenland and Antarctica are almost fully covered in sheets of ice. Others are mountain glaciers. T ey flow


down rugged peaks and can stretch for 120 kilometers (75 miles). Koppes and her team are standing at the foot


of Tyndall Glacier in Chile. T at’s where the glacier flows into a lake. T is part of a glacier is called the terminus. Here, huge pieces of ice can break off , or calve, into the water. One piece nearly hit Koppes’s kayak.


18 NATIONAL GEOGRAPHIC EXPLORER


Michele Koppes lowers herself into an ice cave in a glacier.


Getting Ready Koppes and her team are studying how the glacier moves and changes. T ey plan to climb up the glacier and collect data along the way. Aſt er stowing their kayaks, they check


their gear. Koppes’s backpack overflows with equipment. Some of the instruments are for measuring changes in the ice. Most of her gear is to keep her safe on the ice. She zips up her warm coat. She puts on dark


sunglasses. Sunlight reflecting off the ice can be blinding. Her eyes need protection. Koppes clips herself into her climbing


harness. A coil of rope rests across one shoulder. In her hand, she carries an ice axe. With a nod to her team, they begin the climb.


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