THE BIRTH OF A PLANET Unlike other fields of Natural History, GEOLOGY has no geographic boundaries. Its concern is with the planet. Geologists examine processes that formed and shaped Earth surface and seek clues to the nature depths they cannot visit. While a particular species of bird, fish, or butterfly may be found only near your home, the stony cliffs and shining veins of Patagonia are little different from some you pass daily. Living species adapt local stress, evolving by selection of the fittest for each environment. But the rocks that make up the crust of the Earth, the minerals that make the rocks, are everywhere alike, because the conditions under which they form are the same everywhere. From the earliest appearance, the evolution of living forms has been affected by environment. Variations in climate and topography - desert and jungle. Himalayan peaks and Amazon swamps - have enriched the Earth with innumerable species, each adapted to its ecological niche. Rocks and minerals, on the other hand, heed harsher laws, as elements from the combinations predetermined by the immutable mathematics of chemistry and physics. Beneath the surface, the Earth is like an onion, layered in a series of shells. A short way down, conditions are the same worldwide - heat, pressure, molten rock, inconstant gases, and traces of rarer substances. Elements everywhere join to form the same minerals. We can be sure that when pioneering astronauts disembark on Mars, they will find formations differing little from those they left on Earth. AN EVOLVING SURFACE If we fantasize an all-seeing Methuselah, a chronicler to whom our year is but a second, watching the formation of Earth from distant space, our observer would have been kept very busy documenting this fast-changing planet. He would have noted that much of the surface was covered with a blue skin of water that surrounded a giant, turning island (#Pangaea). The island split along the boundaries of the large areas of crust we call plates,and then the pieces of land came together again, while the crust thickened. This happened more than once in the early days. Ever so slowly, features formed on the flat exposed surfaces, rolling hills with uptilted edges, arching layers rimming low-lying plains intersected by mud-filled rivers running to the seas. From time to time, he might have seen mysteriously glowing rivers near the island edges. Entranced by these events, our far-off viewer would watch as the island surfaces grew green, margins became bay-cusped, and light-hued bars and beaches stretched out to sea. Round elevations became sharp mountains, low-lying valleys were incised and widened by watery scalpels. With mountains growing steeper, exposing layered cliffs of bent and folded strata, no longer was the crust a simple sheet of frozen lava. *Source: Peterson First Guide to Rocks and Minerals by Frederick H. Pough Click the photos to see the source links and their captions. Prepared by: Group 1 of BS Geology 1-A
Posted on: Sat, 05 Jul 2014 11:48:56 +0000
Trending Topics
Recently Viewed Topics
© 2015