The Earth reveals its secrets
22 December 2007
Catherine Brahic
<http://environment.newscientist.com/channel/earth/mg19626355.600-news-review-2007-the-earth-reveals-its-secrets.html>
"It's like finding out some fascinating little secrets about your own
mother.
This year, our life-giver, the Blue Planet, revealed a host of details
about herself. We learned where to find the clearest seas, the oldest
piece of the Earth's crust, why it hums, and how many volcanoes sit on
the ocean floor. We now know how the weather makes the days a tiny bit
longer, while climate change will make them shorter. Oh, and Earth is
smaller than we thought.
The planet's clearest ocean waters lie in the middle of the southern
Pacific. A lack of chlorophyll and nutrients also makes them the most
lifeless, giving them an eerie violet hue that can be picked out from
space. The record-breaking crust, at 3.8 million years old, was found
in Greenland.
As for that mysterious hum, computer models show it is caused by
turbulent water pounding the ocean floor. A review of sonar data
reveals there are more than 200,000 undersea volcanoes, 10 times the
number expected. Most were too small to have been detected before.
In June, new video technology revealed sprites in their full glory as
these gigantic flashes of light tear through the thin air above
thunderclouds. A new type of polar aurora was also revealed, thought
to be caused by electrons from the solar wind reaching a different
part of the atmosphere from the source of most auroras.
Why do El Niño events make the days a wee bit longer? It's because
they generate strong westerly winds that speed up the rotation of the
atmosphere. The Earth and its atmosphere system always retain the same
total angular momentum, so Earth has to slow down to compensate,
adding roughly 1 millisecond to each day during an El Niño. That will
partly be offset by climate change, as warmer oceans will shift some
of the mass of the oceans towards the poles. Like an ice skater
tucking her arms into her body, the Earth will spin faster, losing 2.3
milliseconds every 100 years.
What of our planet's size? A new, more precise measurement of her
diameter revealed she is 5 millimetres smaller than we thought."
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