Icebergs

Science
 * [[image:wikistange_small.jpg]] || [[image:home_button.jpg link="home"]] || =Icebergs= ||

Record your findings on the **//Beware of Icebergs!//** tip sheet. Use key words to record facts about icebergs in the "Facts" column. Then guess about the risks each fact poses in the "Potential Risks" column. What actions could a ship crew take to avoid those risks? Write your ideas down in the "Recommended Actions" column.


 * [[image:http://www.strategicva.com/images/iceberg.jpg width="496" height="610"]] || =Where do icebergs come from?=

Most of the icebergs found in the North Atlantic come from about 100 glaciers along the Greenland coast. A few others can be traced back to glaciers in the Eastern Canadian Arctic Islands. The glaciers of western Greenland, where 90% of Newfoundland's icebergs originate, are amongst the fastest moving in the world, up to 7 km per year. As the ice advances into the sea, it breaks off because it is no longer supported from below.

=Do we know many icebergs are there at any one time?=

Approximately 40,000 medium to large sized icebergs calve annually in Greenland and about 1 to 2% (400-800) of those make it as far south as 48 degrees north latitude (St. John's). The numbers vary greatly from year to year and seasonally. Spring and early summer are the best times for icebergs. Icebergs that drift into shipping areas are closely monitored from ships and from satellites. Nobody wants another Titanic disaster! || =Weird Iceberg Facts=
 * [[image:http://imagecache01a.allposters.com/images/pic/PA/6445019~Penguins-Diving-Off-Iceberg-Posters.jpg]]


 * Antarctic ice shelves may calve icebergs that are over 80 kilometres long. If that was a flat road, it would take you about 17 hours to walk from one end to the other
 * Almost 90% of an iceberg is below water--only about 10% shows above water.
 * There has been at least one recorded murder on an iceberg.
 * In the 6th century an Irish monk recorded that he "passed by towering crystals that rose up to the sky" when he wrote an account called "Voyage of Saint Brendan the Abbot". During voyage, he recorded that his boat " was raised up on the back of a sea monster, passed colossal crystals that rose from the sea and had blazing rocks thrown at it by the natives of a large island." Historians think he was referring to whales, icebergs and Iceland's volcanoes. It is possible that Saint Brendan discovered America almost a millennium before Christopher Columbus got there.
 * During the Second World War there was a top secret plan (called Habbakuk) to use icebergs as aircraft carriers.
 * In June 1875 the schooner "Caledonia" sank off Newfoundland, but the crew of 82 all managed to climb to safety on an iceberg. They were all rescued.
 * The word "iceberg" probably comes from "ijsberg", which means "ice hill".
 * Melting iceberg ice makes a fizzing or pinging sound. This is caused by the popping of tiny compressed air bubbles in the ice. The air that escapes is, of course, as old as the ice. It may have been trapped there for 15,000 years or more!
 * Icebergs may also make sudden very loud booming and cracking sounds without any sign of movement or calving. The sounds are caused by stress cracks forming in the ice. It's a very scary experience when you are close to the berg and it starts making noises!
 * In Newfoundland iceberg ice is now a commercial product. Ice is collected and sold as bottled water and used in the production of vodka.
 * Growlers, or small iceberg pieces, really do make a growling noise when they bob up and down into the water.



=Why does glacial ice look blue, but snow looks white?=

Glacial ice only looks blue when it has become very dense. Years of compression slowly increase the density of the ice, from loose and fluffy snow to extremely dense ice. As it is compressed, the air trapped between the original snow flakes is forced out. When glacier ice becomes extremely dense, the properties of the ice change. It now absorbs all the colours in the spectrum except blue, which it reflects. This is why it looks blue. From this, you have probably worked out that it's the trapped air in snow that makes it reflect almost all the spectrum and appear white. So, white ice is new ice, blue ice is old ice. || =How old are icebergs?=

Icebergs usually take about a year between being calved from a glacier and reaching Newfoundland. They usually hang around in cold arctic bays melting slowly (or not at all in winter) for about a year, then eventually move through the Davis Strait and into the Labrador current. Once they pass the Davis Straight they usually have about one year left before they melt. The further south they drift, the quicker they melt. The glacial ice that actually forms the icebergs though may be more that 15,000 years old.

=How much does an iceberg weigh?=

It all depends on how big they are! The larger ones can weigh more than 10 million tonnes. Icebergs are classified according to size, and are named as follows...

Very large, large, medium and small bergs. Icebergs smaller than 'small bergs' have interesting names. After small bergs there are " bergy bits" and finally "growlers". Growlers are about the size of a small car.

If you really want an average value, the average iceberg weight for the Grand Banks area is one to two hundred thousand tonnes.

=How cold are icebergs?=

Inside the iceberg the temperature is about -15 to -20 degrees C. The surface temperature is determined by the temperature around the berg.

=How big was the largest iceberg ever recorded?=

The largest Northern Hemisphere iceberg on record was discovered near Baffin Island in 1882. It was 13 km long, 6 km wide and its height above water was about 20 m. To put that into context, if you melted a berg that big, you'd have enough water for each person in the world to drink two litres a day for 2 years!

In Antarctica the bergs can be even bigger. In 1987 an iceberg with an area of 6350 square kilometers broke from the Ross Ice Shelf. That berg had a mass of around 1.4 trillion tonnes and could have supplied everyone in the world with 2 litres of water per day for almost 330 years! ||