Document Actions
1.7 Icebergs
Icebergs are fascinating structure with wondrous beauty and power. Students can investigate what icebergs are made from, why four-fifths of an iceberg is underwater and research how icebergs float and melt.
Iceberg near Davis.
Photo: Dave Mccormack
|
- Discuss whether icebergs are made from freshwater or saltwater, and why.
- Demonstrate the principle of four-fifths of an iceberg being underwater by floating an ice block in a glass of water. Have students predict, observe and record whether the ice block will float in freshwater, and then in saltwater. (Note that most icebergs have a density that is a little below that of pure ice because they contain some entrapped air. Tabular bergs have a top layer of compacted snow 50 metres or more thick, which is less dense than ice.) Estimate the proportion of the ice block that floats above the surface. Why are icebergs dangerous to shipping? What famous vessels have been lost to icebergs?
- Students could research the floating properties and melting rates of different shaped ice bergs. In groups they could then brainstorm how they could make different shaped icebergs and how to tell how much is submerged. (Hint: use overflow cans and apply Archimedes' Principle (which states that the apparent loss in weight of a body immersed in a liquid is equal to the weight of the liquid displaced - so if the weight of the iceberg is less than the upwards force of the water, it will float partly above the surface). The students could also use this to tell if water takes up more or less space than ice.)
Read all about the recent calving of several immense Antarctic icebergs from the Amery Ice Shelf in the media release Successful season winds up.
Check out the Gander Academy site for information about icebergs, including photos (even one of the iceberg that sank the Titanic).
ISSUE - Icebergs
Grounded icebergs off the Antarctic coast.
Photo: Diana Calder
|