When a large piece of freshwater ice breaks off a glacier or ice shelf, it will float in the open water becoming icebergs. They are commonly found in polar regions, especially the Arctic and Antarctic, where massive glaciers meet the ocean.
Icebergs can vary in size and shape, but they all share a common anatomy:
Visible Tip:
Sail: The visible part of the iceberg above the waterline is known as the "sail." This is the smallest part of the iceberg and is often what ships and observers see first. Its size and shape can vary widely.
Submerged Base:
Keel: The "keel" is the underwater portion of the iceberg, and it is much larger than the visible tip. The keel is responsible for maintaining the iceberg's stability by counterbalancing the weight of the sail above the waterline.
Waterline:
The waterline is the boundary between the visible portion of the iceberg and the submerged part. Typically, about 90% of an iceberg's mass is beneath the water, while only about 10% is above the surface.
Layers and Strata:
Icebergs are often composed of distinct layers and strata, which can be visible when the iceberg has broken apart. These layers are caused by the accumulation of snow and ice over many years, with each layer compacted and compressed over time.
Bergy Bit and Growler:
Smaller ice fragments that have broken off from an iceberg or glacier are known as "bergy bits" and "growlers." Bergy bits are larger than growlers, but both can be hazards to ships, especially in areas with heavy iceberg concentrations such as the North Atlantic.
Shapes and Features:
Icebergs come in various shapes, including tabular (flat-topped), domed, wedge-shaped, and irregular. Some icebergs may have unique features like tunnels, arches, and large overhanging sections.
Colours:
Icebergs can appear in various shades of white and blue. The blue colour comes from compressed ice, which scatters and absorbs light differently from ordinary ice. The amount of blue in an iceberg can vary depending on its age and composition.
Sizes:
Icebergs can range in size from small chunks to massive structures spanning several kilometres. The largest icebergs are known as "tabular icebergs" and are typically flat and extensive.
Movement:
Icebergs are not stationary; they can drift with ocean currents and winds. Their movement can be unpredictable, making them a potential hazard to shipping.
Melting and Calving:
Icebergs gradually melt as they float in warmer waters, causing them to change shape and size over time. They can also break apart in a process known as "calving", where large chunks of ice break off from the main iceberg.
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