Tuesday, July 14, 2009

More than you wanted to know about what I learned in school today

Harvey's friend (whose name escapes me at the moment, but Harvey will surely supply it) is a professor of geology at CSU Chico. At my request he recommended a textbook for me to read, "New Views on an Old Planet" by Tjeerd van Andel.

Too much to tell but I will give an example or three.

As you know plate tectonics is caused by convection of semi-molten rock in the mantle of the earth. This causes earthquakes and volcanoes at the joints between the plates. Less well known is what keeps the earth's core still molten after 4.5 billion years and powers the convection - the radioactive isotopes in the core. As they decay they radiate heat.

He shows by simple arithmetic and the half-lives of the main radioactive isotopes involved that the amount of heat generated in the past has to have been significantly higher than it is today. Which means that there was more convection in the mantle and that it was shallower than it is today. Which means that there were far more and smaller continents in the past than there are today.

Which means that ocean currents flowed smoothly around the planet and global weather had relatively small gradients with latitude - no ice at the poles and relatively mild weather at the equator.

With the continuing decay of the radioactives in the core of the earth the amount of heat in the core diminished, continents continued to drift, albeit more slowly, and became bigger. Recent developments, particularly the emergence of the Isthmus of Panama and the Suez Peninsula, have broken up the around-the-world ocean currents that kept climates equable as late as the mesozoic (loosely speaking, the age of dinosaurs).

These east-to-west currents in our era have been replaced by south-to-north currents caused by the fact that the earth has a glaciated continent at the south pole but none at the north pole. Van Andel says that cold water sinks all around Antarctica and forms seabottom cold currents that flow north. Sea surface warm currents flow south to replace the cold water flowing north , which makes a constant circular convection. There are regional currents as well, such as the Gulf Stream.

According to van Andel the cold currents from Antarctica, together with the shutting down of the equatorial currents, are the main determinants of climate and explain why the earth has grown so much colder and drier during the cenezoic (the past 60 millions of year - again loosely, the age of mammals).

[As an aside I should mention that this has no relevance to the global warming debate because the time scales are so different. Five thousand years of global warming might be more than enough to wipe out us and many other species, but would be too brief a blip to even show on van Andel's graph of temperatures.]

However the sea floors are not uniform. There are two major bottlenecks to the seabottom cold currents; van Andel calls them "gateways". One is west of Samoa, the other east of the Falklands.

If these were disrupted, the current flow would cease. The climate of the earth would be radically and fairly quickly transformed. Permanently, in human terms. Did I say "if"? Given what we know of plate tectonics, I meant "when".

Another gem -
He explains that the early biological and pre-biological processes that were the earliest history of life cannot take place in the presence of oxygen. But that those very processes generate oxygen. So why didn't early life poison itself by oxygenating the atmosphere and oceans early on and become extinct before it could evolve metabolic pathways that could use oxygen? What are we all doing here?

It turns out according to the going theory that oceans contain lots of dissolved iron and that continental rock contains lots of iron as well. Iron readily oxidizes in the presence of oxygen. So for more than a billion years, life got away with surviving because there was enough iron in erosion products like sand and clay and in sea water to absorb all of the oxygen.

Oxygen accumulated only slowly from 2 billion years ago to half a billion ya as the surface of the earth and the oceans began to run out of unoxidized iron. Since then there has been a rapid accumulation to more than fifteen times as much as when the earth was 90% as old as it is now and over a hundred times as much as when it was 80% of its current age. Which is to say, in geological times scale the atmosphere is going through a radical transformation RIGHT NOW.

Another thing -
There is no explanation for the composition of the rest of the earth's atmosphere. No theory to explain it works. (As of 1985 when "New Views" was published.)

Similarly, no theory explains why the oceans are not far saltier than they are.

And in closing, did you know that the sun evolves as well? It is 30% brighter now than it was a billion years ago, and twice as bright as it was when the earth was half its present age. No one knows how this may have affected life and evolution.

One speculation is that a dimmer, cooler sun would have produced less ultraviolet,which is mutagenic. But before there was oxygen was also before there was an ozone (Ozone is O3) layer in the atmosphere. Which means that though there was less UV, more of it reached the surface of the earth.

So one guess (mine, not van Andel's) is that eukaryotic cells (like ours) with their large, easily-disrupted genomes could not arise until there was an ozone layer.

"New Views on an Old Planet" is chuckabluck (chocablock?) with startling new things to think about on every page. By the way all, all, of this took place right where you are now*, among other places. Not far away. Right here. It is all still going on, right now.

*Unless you are in Ireland. Ireland has always been a stupid, miserable shithole where nothing good or interesting has ever happened.


  1. Anonymous11:07 PM

    Bottom line...is this good or bad for the Jews?

  2. Good for the Jews. Fossil fuel was laid down in the earth in the Pennsylvanian and Mississipian eras (jointly 'the carboniferous era') in the latter palaeozoic. No more has been or is being made. When that's gone, it is all gone.

    The Arabs would then have to live on what they can produce competitively. Without oil being of any value they would rapidly revert to their earlier status as the more backward parts of the Ottoman Empire.