Glaciers are very important. They have a large effect on the environment. They do this because they are very large and heavy. When they move, they erode mountains and land. Also, since they froze long ago, snow crystals and air bubbles inside are kept in good condition. These can provide a large amount of information for scientists. Recently glaciers have been melting more than they did in the past. Many scientists think this is happening because global warming is changing the climate.