A glacier is like a frozen river. Many countries do not have any glaciers. A glacier starts in very high mountains where there is snow and ice all the year. The snow and ice starts to move down a valley that has been made by a fast-flowing stream. As the ice starts to slide down the mountainside, it does not flow around the rocks; it pushes the rocks out of the way. As a glacier moves, it picks up more ice and gets bigger and bigger. A big glacier cuts through the soil and softer rock of the valley and piles up the rocks on either side, or pushes them in front of it. When a big glacier melts, it leaves a valley of a deep U-shape. Many valleys like this were made in the Ice Ages. In mountainous countries like Switzerland many people live in the valleys that were made by glaciers. Some of the deepest valleys in the world were made by glaciers. The fjords of Norway and "sounds" of New Zealand are where glaciers went into the sea. 