We can infer from the passage that glaciers ______.

Overpopulation and environmental pollution are constantly decreasing the world's drinking water reserves; consequently, the vast store of water contained in glaciers is a resource of inestimable value. Yet, since these immense masses of ice are difficult to penetrate and explore, our knowledge about them is limited. An economical approach to expanding this knowledge, according to a group of scientists, would be to offer climbing expeditions the opportunity of combining mountaineering and science. They believe that, by using the methods and equipment described in their project, small groups of climbers can in a short time collect valuable data about glaciers, even under extreme conditions.