Cold hard facts
By CHRISTINE JEFFERS
Shunpiking Magazine, No. 10, December, 1996
How relative is an Ice Age?
A period when part of the Earth is permanently covered by ice is called an Ice Age. We are living in an Ice Age at the moment. Today, permanent ice covers about ten per cent of the Earth's surface. During the last Ice Age, over twenty per cent of the planet was engulfed in ice. The average temperature was about three degrees lower than it is today.
How is an iceberg formed?
When an advancing glacier reaches the sea, the massive weight of the ice breaks free and floats away from the landforms. These bergs can range greatly in size. Smaller masses also "calve" from icebergs -- depending on their sizes, they are "growlers" or "bergy-bits".
Why does salt melt ice?
The presence of dissolved substances in water reduces the temperature at which water will freeze. Based on the same principle, rock salt is used with crushed ice in ice cream makers -- in a ratio which reduces the ice to a slush consistency as it gradually freezes the cream mixture.
Why do skates slide so easily on ice?
The commonly held belief is that the pressure exerted by the sharp skate blade forces an instantaneous melting of ice beneath it, creating a thin, slippery film of water on which to glide.
Sound plausible? Not to some experts, who in their hair-splitting quest for accuracy argue that a blade's friction on ice causes heat, creating a water film generated at the interface -- or shear -- of the ice. There is also an effect called "surface melting": a solid will sometimes develop a liquid film on its surface at a temperature below the solid's normal melting point; this phenomenon may be a factor. Other researchers suggest that a skate blade may slide over microscopic balls of ice, or even on a cushion of air vapor. Could that be how Elvis, Kurt and Kristy manage to look so weightless when they perform?
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