Icebergs

I'm hoping that I still have students and teachers that are following the blog as I share out some of the educational postings. Today, I'm going to focus on Ice. Believe me, in Antarctica there is plenty of ice in all shapes and sizes. I use this picture from Wikipedia to demonstrate how much larger an iceberg is below the surface of the ocean.

Occasionally, huge pieces of floating shelf ice break loose and drift away in the currents. These pieces of ice are called Tabular Bergs or Tabular Icebergs, and can be enormous, perhaps hundreds of square kilometers in surface area, and may drift for years before melting or becoming grounded. These are not to be confused with regular icebergs, which break off from glaciers that reach the sea. Not all Antarctic icebergs are of such huge proportions. Some are much smaller, for icebergs are simply pieces of ice, large or small which have broken (calved) off the ice sheet, ice shelves, or glaciers, and float in the sea. By definition, however, an iceberg is suppose to measure more than 100 square meters (1,100 square feet) in area, and stand more than five meters (16 feet) above the surface.

Indications of an iceberg's history can be gleaned by observing its color (which depends on age, density and air content of the ice), or dark bands that reveal the presence of glacial moraines or volcanic ash, or its general shape and sculpturing. Sometimes horizontal or oblique water-lines at different levels show where the iceberg has melted and then tilted as it adjusts its center of gravity (AP pg. 32,33).

Most of the information I could find, including a presentation that was given to us the night before heading into Iceberg Alley, classifies icebergs into roughly seven categories.

1. Tabular - These are large with flat top resembling a huge tablet. Have usually broken away from ice sheets or an ice shelf

2. Non-Tabular - Often referred to all icebergs that are not tabular

3. Blocky - Flat topped and block shaped with steep sides

4. Dome - Rounded in the middle while tapering to the edges

5. Wedge - Top narrows to a pyramid point

6. Drydock - An iceberg eroding to the point that it forms and enclosure much like a harbor. Thus the name "drydock"

7. Pinnacle - Having one or spires, often resembling a castle.

Other terms used to classify ice at Antarctica:

1. Anchor ice - Submerged ice that is attached to the sea bed

2. Glacier - A mass of snow and/or ice moving from higher to lower ground. Sometimes a glacier can float out onto the sea

3. Pancake ice - a form of ice that consists of round pieces of ice with diameters ranging from a few inches to many feet in diameter

See if you can pick out and identify the different types of icebergs!