Different methods of dating rocks
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The second goal is to illustrate the changing distribution of mountains, lowlands, shallow seas, and deep ocean basins through time.The past positions of the continents can be determined using the following five lines of evidence: paleomagnetism, linear magnetic anomalies, paleobiogeography, paleoclimatology, and geologic history.
The age of these linear magnetic anomalies can be determined using fossil evidence and radiometric age determinations.
Other paleogeographic features change very rapidly and, therefore, any map, at best, is an approximation.
In this regard, the Earth, since the early Precambrian, has been divided into deep ocean basins (average depth 3.5 km) and high-standing continents (average elevation about 800 meters).
Less extensive mountains can also form when continents rift apart (e.g.
East African Rift), or where hot spots form volcanic uplifts.
Because these magnetic anomalies form at the mid-ocean ridges, they tend to be long, linear features (hence the name "linear magnetic anomalies") that are symmetrically disposed about the ridges axes.
The past positions of the continents during the last 150 million years can be directly reconstructed by superimposing linear magnetic anomalies of the same age.
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.
The ancient distribution of these, and other, rock types can tell us how the global climate has changed through time and how the continents have travelled across climatic belts.
In order to reconstruct the past positions of the continents it is necessary to understand the development of the plate tectonic boundaries that separate continents and bring them back together again.
The Earth's climate is primarily a result of the redistribution of the Sun's energy across the surface of the globe.