Remember on the 9th or 10th of November I said the Alps were no longer grwoing due to plate tectonics. When I first read the article below, I thought I had made a mistake, but on closer inspection, I found I wasn’t!
From http://www.sciencedaily.com/releases/2009/11/091105121207.htm
ScienceDaily (Nov. 6, 2009) — The Alps are growing just as quickly in height as they are shrinking. This paradoxical result comes from a new study by a group of German and Swiss geoscientists.
The formation of the Alps through the collision of the two continents Africa and Europe began about approximately 55 million years ago. This led to the upthrusting of the highest European mountains, which probably already achieved its greatest height some millions of years ago. At present, however, the Swiss Alps are no longer growing as a result of this tectonic process.
But Swiss geodesists, who have already been measuring the Alps with highest accuracy for decades, have observed, however, that the Alp summits, as compared to low land, rise up to one millimetre per year. Over millions of years a considerable height would have to result. But why then are the Alps not as high as the Himalayas? This is because the mountains eroded at almost exactly the same speed as they were being built.
How does it come about now that the Alps erode at the same speed that they rise? “Here pure upthrusting forces are at work. It is similar to an iceberg in the sea. If the top melts, the iceberg surfaces out of the water increases by almost the same share,” explains von Blanckenburg.
Thus this paradoxical situation with the Alps that through wind, water, glaciers and rock fall, they are being constantly finely eroded from the top but on the other hand, regenerated from the Earth’s mantle. This phenomenon, even if already postulated theoretically has now been proven for a complete mountain range for the first time.
Thus, the Alps are constantly rising, although they have been deemed “dead” in a tectonic sense ( because they plate movements have ceased a long time ago). Instead of plate forces it is the strong climatic variations since the beginning of the so-called quaternary glacial before approximately 2.5 million years, to which mountain slopes in particular have been reacting so sensitively. This holds the Alps in motion.
Think ships: if you laden a ship with a heavy load, it sinks down low in the water. If you take out some of the cargo then the ship will rise up higher in the water. But if the stuff you remove from the ship is only from the top deck, the height of ship + cargo will get less, but the height of ship above the water will be about the same as it was before.
What in effect they are saying is imagine the Alps as a piece of crust ‘floating ‘ on the mantle. As the mountain tops are eroded, the overall mass decreases and so the Alps ‘float’ higher than before.
