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Archive for December, 2010

Geology of Colombia South America

After reading about Our Lady of Las Lajas, (our Lady of the Rocks) I decided to learn something about the geology of Colombia, particularly around Ipiales. What sort of stones might there be in Colombia, I wondered, and are any of them deep blue shales? Here is the Las Lajas image, composed entirely of stone, except for the crowns, added later and seeming somewhat adrift on the glorious heads of the mother and child. (The other two figures are St. Francis and St. Dominic.)

Our Lady of Las Lajas 02

Lying as it does at the foot of the Isthmus of Panama. Colombia has the distinction being formed at the intersection of at least three tectonic plates: the Nazca Plate under the Pacific Ocean, the Caribbean Plate on the eastern side of the isthmus, and the South American plate to the south. The Nazca plate apparently first pushed against the South American plate in the deeps of time, over 500 million years ago, which is about when the supercontinent of Pangaea formed and before it broke up into the northern semi-supercontinent of Laurasia and its southern counterpart, Gondwana.

Laurasia included North America, and Gondwana included South America. Both of them had to break apart along a north-south seam, releasing Eurasia and Africa westwards, whilst also coming together from north to south, thus creating the double continent of the Americas, with Panama at their juncture.

Panama, therefore, is at the junction of several tectonic plates whose collisions belong to various episodes of tectonic shift over half a billion years. Looking today from above, one may think of it as a delicate strand that connects two continents; in fact it is probably not much more delicate than Italy which also lies at a junction of three tectonic plates a fact which accounts for its world reputation in beautiful marble.

The Andes mountains are the most striking feature of Colombia and also the location of most of her cities. The west coast is jungly and wet; the eastern plains range from something like savannah in the north, to the upper reaches of the Amazon jungle in the south; but even the drier regions have annual flooding that makes farming difficult. So the mountains are the location of Colombia’s cities and it is rugged going from place to place.

The city of Ipiales is on the western side of the Andes Mountains, just above the jungles of the Pacific coast, and just over the border from Ecuador. The little town of Potosi is six miles east. Perhaps both towns were small in 1754.

Blue shales

I still do not know anything about blue shales. Somerset England has a lovely formation from the early Jurassic, called the Lias. The stone is very blue.

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A recent article in the national news expresses the conviction that scientists have wrongly “assumed” that intelligent life could not exist on a planet orbiting a red dwarf star. Since there are so many red dwarfs, they have thus limited their search, and perhaps this is why they can’t find extra-terrestrial life.

There are several things wrong with this assertion, starting with the word “assumed.”

Scientists didn’t merely assume; they had thoughts based on rational considerations. Let me share a few of those considerations with you so you can understand how simply and completely this issue has been misrepresented.

A red dwarf star is not as hot as our sun. That’s why it is red. Therefore a planet orbiting a red dwarf must stay a lot closer to its sun in order to have the requisite water available for life. Most people who have any idea of what water means to chemistry and to life agree that liquid water is absolutely essential for life, and for any meaningful advances in life, that water has to be on the surface of the planet, not just under a mile of ice.

So, very well, the Goldilocks zone (not too hot, not too cold, just right) of a red dwarf star is much closer in than the Goldilocks zone of a sunlike star. That closeness is already sort of vulnerable because things happen in the universe, like comets bumping stuff, and you want to be where you can survive a few bumps, not where one bump might throw your orbit spiraling into your sun; so that’s one problem with a red dwarf. But this kind of author (Seth Borenstein wrote the AP article) is thinking that there are so many red dwarfs, we really should take a look, and not “assume” they don’t have habitable planets.

But now comes another consideration. When a planet is closer in, the tidal drag between planet and star is much stronger. And when the tidal drag is stronger, the spin of the planet slows down. Eventually it stops, or rather, the spin of the planet becomes the same as its orbit so that the planet turns just one face to its sun, and the other face away. (Our moon always turns the same face to the earth because of this tidal drag.)

Do you see a problem with this?

One face, turned to the little red sun, is going to get very, very hot; the other face, turned away, is going to get very, very cold. And all the world-encircling winds that we have on earth: the Hadley cells and the polar cells and the jet stream and so forth, are not going to be able fix it, because they depend on the Coriolis effect which depends on a spinning planet. So the “average temperature” of the red-dwarf’s planet might be ok, but the hot side will be too hot and the cold side will be too cold, and the little line between will be “little” and vulnerable and perhaps also stormy with the air from two sides meeting and mixing and raining and hailing, and snowing and melting in a great rush and tumult.

But really it wouldn’t even be that way on the line between, because soon enough, the hot side will just be dry, and the cold side will have all the water, all locked up as ice. This has to happen, because any water that strayed to the hot side would be evaporated, and as soon as it migrated to the cold side, it would fall as snow and never come back. All this would take place during the tidal locking ages, and then the possibility of life would be over.

The astrobiologists who left red dwarfs out of the list of places to look for intelligent life had reasons for their omission; it was not an assumption; it was a considered omission, and the reasons for it are not difficult to understand.

If you want to know more about it, read Privileged Planet by Guillermo Gonzales and Jay Richards. You will like it.

 

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