What does the word iceberg make you think of ? Do you think of a large block of ice in a cold northern ocean? Or do you think of something that ships can crash into? While these are both correct, in truth there's far more to icebergs than meets the eye. According to scientists, only the largest blocks of ice count as icebergs. They must rise at least 5 meters above the water and be 15 meters wide at the water line. But only about 10 percent of an iceberg can be seen. The rest lie beneath the water. Icebergs begin froming when layers of snow fall year after year without melting. The snow is pressed together into large blocks of ice called glaciers. When chunks of ice break off these glaciers, icebergs are born. In Greenland alone, about 40,000 icebergs are formed each year. Since they began as snow, icebergs are made of fresh water, not salty ocean water. Tidy bubbles of air inside the ice give them their white color1. While most icebergs are white, some are blue because they have melted and frozen again. This action allows the air bubbles to escape. Other icebergs have brown, black or yellow parts because of dirt mixed with the ice. Algae   can also get trapped in the underwater parts of an iceberg. If the iceberg turns over, all or part of it is green! Icebergs can be flat, cube-shaped, round like a turtle shell or U-shaped. Some even look like mountains. The large underwater parts of icebergs are hard for ships to avoid. They have destroyed and sunk many ships, including the Titanic. As a result, the International Ice Patrol now monitors icebergs in areas with heavy ship traffic. But there's yet another side to icebergs. Many microscopic   animals live inside icebergs and in the water around them. These creatures feed on minerals that the icebergs store and release as they melt. Scientists are still studying all the ways icebergs affect sea life. Why does the passage begin with questions?
To attract readers' interest in icebergs. To show readers icebergs are dangerous. To tell readers icebergs are large blocks of ice. To encourage readers to see icebergs by themselves.