Mt st helens radioactive dating

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Such a large variety of igneous rocks exists that it is logical to assume an equally large variety of magmas must also exist.However, geologists have found that various eruptive stages of the same volcano often extrude lavas exhibiting somewhat different mineral compositions, particularly if an extensive period of time separated the eruptions.Evidence of this type led them to look into the possibility that a single magma might produce rocks of varying mineral content. Bowen discovered that as magma cools in the laboratory, certain minerals crystallize first.A pioneering investigation into the crystallization of magma was carried out by N. At successively lower temperature, other minerals begin to crystallize as shown in Figure 3.6.Lava erupting earlier would come from the top of the magma chamber, and lava erupting later would come from lower down.

Here I want to concentrate on another source of error, namely, processes that take place within magma chambers.To me it has been a real eye opener to see all the processes that are taking place and their potential influence on radiometric dating.Radiometric dating is largely done on rock that has formed from solidified lava.During the last stage of crystallization, after most of the magma has solidified, the remaining melt will form the minerals quartz, muscovite mica, and potassium feldspar.Although these minerals crystallize in the order shown, this sequence is not a true reaction series.

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