26. Over a number of generations, scientists investigating Earth’s long history

Question

26. Over a number of generations, scientists investigating Earth’s long history have summarized their findings as the geologic column, which is a description of the sequence of major events shaping our planet and its living inhabitants. Upon what two major sources of evidence is the geologic column based? (1 point) 1. the sequence of fossils in sedimentary rocks 2. the written records from ancient cultures 3. dates derived from radioactive decay of certain minerals in the rocks 4. magnetic reversal patterns in sea floor rocks Answer choices: a. 1 and 2 b. 2 and 3 c. 2 and 4 d. 1 and 3 e. 1 and 4

Explanation / Answer

Answer d 1 and 3:The geological column or timescale is that which relates the geological strata with time. This is used to relate the timing and relationship of different events in the earth's history. The oldest event are at the bottom and the youngest event are at the top of column. The rocks that contain index fossils have been divided into eras. This fossiliferous layers have been correlated worldwide and based on that the geological column has been constructed. The part of the time scale which is prepared by the use of fossils is 570 million years. Most of the index fossils about 95% are marine fossils. This time scale is also prepared by using radioactive dating methods which gives the absolute dating of rocks and is useful especially for the old Precambrian rocks where fossils are not available. This geological time scale represents the entire 4.5 billion history of the earth.

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