If, on average, the Andes has an elevation of 20,000 feet, and it was raised to this level from zero elevation by five feet every 250 years, then1) 20,000 ft / 5 ft = 4,0002) 4000 * 250 = 1,000,000.One million years to raise the Andes from zero elevation at the rate of 5 feet per 250 years.During the first few months of his journey in South America, Darwin became convinced that, exclusively, the Earth's surface changed gradually over long periods because of the continuous effects of surface disturbances such as earthquakes, erosion, deposition, and volcanic activity.
Darwin researched this because he became witness to a major earthquake in Chile, which resulted in new land rising perceptibly from the sea in a very short time. He also found fossil shells 12,000 feet up in the Andes. These two experiences confirmed for him Charles Lyell's concepts in his work Principles of Geology. He came to believe that sudden, short-lived events of great violence were also responsible for the alteration of the Earth's surface. In the Indian Ocean, Darwin also studied the slow and steady formation of coral reefs.
Here he conceived of the idea that the earth was probably thousands or even millions of years old, contrary to the prevailing notions that the earth was just a few thousand years old. On his Beagle journey Darwin collected enough data on geology, which he used as the basis for three books on South American geology.Darwin also eventually challenged and subsequently changed Charles Lyell's view on the formation of coral reefs by volcanic action. According to Darwin, the reefs were part of a process of gradual changes in the Earth's crust, which resulted from corresponding instances of subsidence and elevation in landmasses.
Thus, according to him, because corals grow in shallow water, coral reefs form because they build up on the sea floor as it subsides. He than extended this theory to the formation of atolls, which he said would form as a whole island sank beneath the sea. Darwin's theories on continental change brought him celebrity in scientific circles even before his return from the journey.
