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Only by understanding the regional geological and tectonic evolution of an area can you determine the location and timing of rifting, subduction, continental collision and other major plate tectonic events.Some paleogeographic features change very slowly and are easy to map.Certain kinds of rocks form under specific climatic conditions.For example coals occur where it is wet, bauxite occurs where it is warm and wet, evaporites and calcretes occur where it is warm and dry, and tillites occur where it is wet and cool.The ocean basins, on the other hand, are all less than 150 million years old.Oceanic lithosphere, because it is more dense is continually recylced back into the interior of the Earth.Fluctuations, or "anomalies", in the intensity of the magnetic field, occur at the boundaries between normally magnetized sea floor, and sea floor magnetized in the "reverse" direction.The age of these linear magnetic anomalies can be determined using fossil evidence and radiometric age determinations.
The first goal is to map the past positions of the continents.
By measuring the remanent magnetic field often preserved in iron-bearing rock formations, paleomagnetic analysis can determine whether a rock was magnetized near the Pole or near the Equator.
Paleomagnetism provides direct evidence of a continent's N-S (latitudinal) position, but does not constrain its E-W (longitudinal) position.
In contrast to the continents and ocean basins, which are permanent geographic features, the height and location of mountain belts and the shape of the Earth's shorelines constantly change.
Mountain belts either form where oceanic lithosphere is subducted beneath the margin of a continent, giving rise to a linear range of mountains, like the Andes mountains of western South America, or where continents collide forming, high mountains and broad plateaus like the Himalayan mountains and Tibetan Plateau of central Asia.
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The Earth's magnetic field has another important property.