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What is an Iceberg?

Mary McMahon
Mary McMahon
Mary McMahon
Mary McMahon

An iceberg is a piece of glacial ice which has broken off and become free-floating. Although icebergs are found in the ocean, they are actually made from freshwater, and this contributes to their buoyancy in the ocean. Typically, around one tenth of an iceberg's mass can be seen above the surface of the water, with the bulk of the iceberg being submerged. This explains the common slang term “the tip of the iceberg,” used to describe a situation in which incomplete information about a situation is available.

When an iceberg breaks off in a process known as calving, it sets sail on a slow journey through the ocean. The iceberg will move with the ocean and wind currents, and its lifespan will be essentially indefinite, as long as it is not pushed into warmer regions. Many icebergs lose a bit of volume during the summer months, but as long as they are close to the poles, they can remain quite sizable. Over time, an iceberg may also break up into several smaller segments.

Icebergs.
Icebergs.

Scientists use a variety of terms to classify icebergs. Sizewise, they can be on the small end of the scale, as with bergy bits and growlers, or on the bigger side of the spectrum, with the imaginatively-named “large” icebergs. Icebergs can reach 75 feet (240 meters) in height. These massive chunks of ice can also be classified by shape, with terms like tabular, weathered, wedge, blocky, valley, pinnacled, dry-dock, domed, and arched being used to describe iceberg shapes.

A ship with a hull that has been damaged by an iceberg may have to be repaired in dry-dock.
A ship with a hull that has been damaged by an iceberg may have to be repaired in dry-dock.

People have been observing icebergs for centuries, and noting their role in navigation. In regions where icebergs are abundant, they can represent a serious threat to shipping, because they are difficult to see and challenging to avoid. Historically, numerous ships were lost due to iceberg collisions. In the modern era, ships avoid bergs by taking advantage of tracking data about especially large icebergs, along with utilizing technology which can be used to identify upcoming bergs in the path of a ship.

Icebergs had an effect on several of explorer Ernest Shackleton's expeditions.
Icebergs had an effect on several of explorer Ernest Shackleton's expeditions.

The number and size of icebergs in the world's oceans is closely monitored by researchers and scientists. An iceberg can present a navigation hazard, especially if it pops up in an unexpected place, but large numbers of big icebergs can also indicate that a glacier may be rapidly deteriorating. Several very large icebergs were calved in the early 21st century, including bergs the size of some American states, raising concerns about the health of the world's glaciers.

Frequently Asked Questions

What exactly is an iceberg and how does it form?

An iceberg is a large piece of freshwater ice that has broken off from a glacier or ice shelf and is floating in open water. They form when chunks of ice calve, or break off, from the edge of glaciers or ice shelves, usually due to the natural process of ice movement and cracking. According to the National Snow and Ice Data Center, this process is influenced by the glacier's flow, temperature, and the surrounding water's warmth.

How much of an iceberg is underwater?

Typically, about 90% of an iceberg's volume and mass is submerged underwater, with only about 10% visible above the surface. This is due to the density of pure ice (about 920 kg/m³) being slightly less than that of seawater, causing icebergs to float. The exact ratio can vary depending on the iceberg's shape and density, as explained by the Archimedes' principle of buoyancy.

What are the different types of icebergs?

Icebergs are categorized mainly by size and shape. The two basic types are tabular and non-tabular. Tabular icebergs have steep sides and a flat top, resembling floating platforms, and are typically larger. Non-tabular icebergs include various shapes like domes, wedges, spires, and blocks. The U.S. National Ice Center classifies icebergs by size, ranging from small 'growlers' to massive 'ice islands'.

Can icebergs pose a threat to ships?

Yes, icebergs can be a significant hazard to ships due to their size and the fact that the majority of their mass is hidden underwater. The most famous incident is the sinking of the RMS Titanic in 1912 after it collided with an iceberg. Modern navigation systems and iceberg tracking help reduce the risk, but ships still maintain a safe distance from them as a precaution.

How long can an iceberg last, and what happens to it over time?

The lifespan of an iceberg varies greatly depending on its size, the temperature of the surrounding water, and wave action. Smaller icebergs may last several weeks to a few years, while large ones can persist for more than a decade. Over time, icebergs melt and disintegrate due to the action of waves, warmer water, and air, eventually disappearing completely.

Do icebergs contribute to sea-level rise?

Icebergs themselves do not contribute directly to sea-level rise when they melt because they are already floating in the ocean. However, the glaciers and ice sheets from which they calve do contribute to sea-level rise when they lose more ice to the ocean than they gain from snowfall. According to NASA, melting ice sheets are the biggest contributors to global sea-level rise.

Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a AllThingsNature researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Learn more...
Mary McMahon
Mary McMahon

Ever since she began contributing to the site several years ago, Mary has embraced the exciting challenge of being a AllThingsNature researcher and writer. Mary has a liberal arts degree from Goddard College and spends her free time reading, cooking, and exploring the great outdoors.

Learn more...

Discussion Comments

goldenmist

@softener - As far as I know, it was a huge iceberg that broke off of the Ross Ice Shelf. I think it was in 2000. I can definitely remember that it was about half the size of Wales though -- crazy how those little things stick in your mind.

softener

Is there any information on how big the largest iceberg ever recorded was? I've got a paper due on this next week and I seem to be finding a lot of conflicting information. Can anybody help me out?

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    • Icebergs.
      By: Goinyk Volodymyr
      Icebergs.
    • A ship with a hull that has been damaged by an iceberg may have to be repaired in dry-dock.
      By: Nightman1965
      A ship with a hull that has been damaged by an iceberg may have to be repaired in dry-dock.
    • Icebergs had an effect on several of explorer Ernest Shackleton's expeditions.
      Icebergs had an effect on several of explorer Ernest Shackleton's expeditions.