Iceberg
About 90% of an iceberg is below the water line and ten percent above. Icebergs break off from larger structures made of ice, like glaciers or ice shelves. These are formed by snowfall in very cold places where it will not melt in the summer. The snow builds up and compacts into ice. This is gradually pulled downhill by gravity and into the sea. The ice then falls off and makes icebergs. The icebergs can drift in the sea for years before they have melted completely.