Life in Mid-Pangaea: There Wasn’t Any
If you think that the climate here and there on Earth is not too good, there are times, every once in a while, when the climate is much worse; when parts of the Earth’s land surface become absolutely uninhabitable.
The reason for this arises from the difference between land and water. Water has a higher heat capacity than land has. That is, a given amount of heat is absorbed by water with less of a temperature rise than takes place in the case of land subjected to the same amount of heat. Similarly, if it gets cold, water gives up heat, dropping to a low temperature, but land, giving up the same amount of heat, drops to a considerably lower temperature.
The result is that the ocean is cooler than the neighboring land in hot weather, and warmer than the neighboring land in cool weather. The ocean, when nearby, therefore exerts a moderating influence on the land’s temperature so that the “oceanic climate” of coastal areas and of islands tends to be milder than it would otherwise be.
On the other hand, land that is far from the ocean does not have a chance to have its temperature moderated. It gets good and hot in the summer, and good and cold in the winter. Such regions experience a “continental climate.”
Ordinarily, you would expect the North Pole and the South Pole to be the coldest regions on Earth by the time they haven’t had any sunshine for six months. As far as the South Pole is concerned that’s almost correct because the South Pole is located on a continent. Still, the lowest temperature is not at the South Pole itself, but in that portion of Antarctica that is farthest from the ocean. The temperature there has been observed to be as low as minus 128.6 F.
In the Arctic region, neither the North Pole nor any place near it holds the record for cold. The North Pole is in the center of the Arctic Ocean, the water of which moderates the temperature. The coldest region in the north is in central Siberia, far from the ocean and barely at the Arctic Circle.
The town of Verkhoyansk in Siberia has experienced a temperature as low as minus 94 F in the depth of winter. On the other hand, in the height of summer, that same town can experience temperatures of up to 98 F. That means there is a total range of up to 192 Fahrenheit degrees of temperatures because of the absence of any oceanic effect. (In the United States, it is places like North Dakota that get really cold in winter and really hot in summer.)
But the continents have not always been distributed as they are now. Very slowly, they are pushed here and there by the movement of the huge plates that make up the Earth’s crust. Every once in a long while, they are pushed together to make up one huge super-continent, called Pangaea (from Greek words meaning “all-Earth”). The last time this happened was about 255 million years ago, when the early reptiles (the ancestors of the dinosaurs and of ourselves) were clumping the Earth.
Imagine Pangaea! It was three times as large as Asia and all in one piece. The central portions of Pangaea were perhaps 2,000 miles farther from the ocean than any land surface can be today.
The central regions of Pangaea, if far enough north or south, would get colder than any place on Earth today in the deep winter and hotter than any place on Earth today in the height of summer.
Some scientists affiliated with the Applied Research Corp. and headed by Thomas Crowley have created a model of Pangaea’s climate on a computer and reported on the results this past spring.
As might be expected, the climates in the interior would be ferocious. Summer temperatures may have routinely reached a high of 115 F or even more, and the winters would have been way below zero. If one plots out the portions of Pangaea that would have had temperatures as bad as, or worse than, that of the north central portions of Siberia and Canada, it turns out that these super-uncomfortable regions of Pangaea encompassed at least eight times the areas of such regions on Earth today.
The places in Pangaea that would have been subjected to the highest temperatures were in what is now eastern Brazil and west-central Africa. The places where the greatest temperature range between summer and winter took place were in what is now southern Africa.
Fossil finds are few in those areas; the climate was probably so ferocious in central Pangaea that life simply could not stand it. This is especially likely since central Pangaea would have been so far from the ocean that the rains could rarely reach it no matter which wind was blowing, making it too hot and dry to sustain life.
It was fortunate, then, that Pangaea broke up (as it always had to sooner or later). The fragments of Pangaea are all more moderate in climate than Pangaea itself was, and the rims of the oceans near the land are always richest in life, too, and with many continents there is more ocean-rim than there was with just one super-continent. So life today is better off . . . if only we don’t do anything to ruin things.
