Tuesday, July 15, 2008

National Geographic: Earth: The Biography


Earth: The Biography (Of a Rare Planet)" is a multi-part series from the National Geographic Channel airing starting this week. The schedule is here.

Dr. Iain Stewart (a Scottish geologist) narrates and appears repeatedly, globe-trotting in what seems like a self-date or solitary trip. It seems so far that every episode has some surprises, although some material is repeated among the episodes.

Oceans”, for example, tells us that a several times in history, the Strait of Gibraltar has closed off, locking up the Mediterranean Sea to evaporate into a desert. It fills up when the strait opens (the same may have happened with the Black Sea). Around the Mediterranean there are salt caves, and even a cave of gypsum crystals in Sicily, which is usually not open to visitors because their breath would erode the crystals. I have visited a similar salt cave in Poland, near Cracow and Auschwitz.

The oceans have an underwater current system of feedback loops. These mechanisms explain the Gulf Stream, which warms Britain and western Europe, and various water pooling mechanisms like El Nino. A breakdown in the feedback loops can cause stagnation and death of sea life. In some areas, that could lead to toxic gasses overtaking land

Strube says that much of the water in the oceans could have come from comets earlier in Earth’s history. Sometimes the Moon and Sun line up to produce enormous tidal boars, that cause a destructive reverse upstream flow up the Amazon.

Atmosphere” examines the air from the troposphere through the stratosphere up to the mesosphere. The film shows a free-fall jump from a balloon at 19 miles altitude in 1960, where the balloonist (Kittinger) took 15 minutes to reach earth, his parachute opening just in time over New Mexico. Stube travels to Western Australia to show us stromatolites, covered with a slime produced by bacteria that were perhaps the earliest life form several billion years ago, until they started producing oxygen with a primitive photosynthesis. He also travels to Patagonia to see some of the most violent cloud-to-ground lightning on the planet, caused with Antarctic and Amazonian air masses collide while trapped by the Andes. The lightning extends into the mesosphere with great color shows like disco lasers.

Volcanoes” starts with an examination of the volcano lava lake in a rift volcano in Ethiopia. (There is another such lava lake in Mount Erebus in Antarctica, shown in the recent film “Encounters at the End of the World” – July 12 on my movies blog). The hour examines how volcanoes helped populate the earth’s atmosphere with carbon dioxide, getting us out of “snowball earth” 700 million years ago. The movie shows how subduction volcanoes like the Cascade volcanoes in Washington state act as a natural thermostat maintaining the carbon dioxide balance in the Earth’s atmosphere. At the end of the movie, a time lapse sequence is shown of the growth of the lava dome in the caldera of Mount St. Helens after its 1980 eruption.



Rare Planet” develops the idea that Earth really may be “special” and rare or alone in the Universe. Stewart starts with the idea that when the Sun was about 1 billion years old, Earth was much smaller and had a twin, Thea, that lagged behind and eventually collided with it, forming a larger Earth with an iron core and unusually strong magnetic field. It also form an unusually large Moon, which produced unusually strong tides. This help set up an environment unusually lucky for advanced life, at least able to get beyond bacteria. Earth had to be stable most of the time, but occasionally needed a real shock (like an asteroid hit) to remove most species and allow new ones to develop. The last time this happened was about 65 million years ago with the asteroid hit near Yucatan that wiped out the dinosaurs.

Here is a blogger entry on this theory about the formation of the Moon.



Ice” has Stewart doing some icefall climbing with crampons, and a British friend climbs Half Dome in Yosemite, which was carved by ice. He discusses the ices ages, and a huge “ice age flood” that scoured out what would become some of the Great Basin with a 60 mph wall of water several hundred feet high. He also explains how the Gulf Stream may have contributed to ice ages, by bringing warm water to polar regions. He explores the Greenland ice cap, with the concerns over its melting, and shows some of the same maps (as did Al Gore in “An Inconvenient Truth”) of coastal inundation around the world that result from global warming. He makes a relative obscure point: glacier ice consists of snow from which all the air has been removed or squeezed out.

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