How do we know the age of the surfaces we see on planets and moons? If a world has a surface as opposed to being mostly gas and liquid , astronomers have developed some techniques for estimating how long ago that surface solidified. Note that the age of these surfaces is not necessarily the age of the planet as a whole. On geologically active objects including Earth , vast outpourings of molten rock or the erosive effects of water and ice, which we call planet weathering, have erased evidence of earlier epochs and present us with only a relatively young surface for investigation. One way to estimate the age of a surface is by counting the number of impact craters. This technique works because the rate at which impacts have occurred in the solar system has been roughly constant for several billion years.
Potassium-Argon Dating Methods
Radiometric dating methods | Geology (modification for Lehman College, CUNY)
By international agreement , Precambrian time is divided into the Archean Eon occurring between roughly 4. After the Precambrian, geologic time intervals are commonly subdivided on the basis of the fossil record. The paucity of Precambrian fossils, however, precludes the creation of small-scale subdivisions epochs and ages in this time period. Instead, relative chronologies of events have been produced for different regions based on such field relationships as unconformities interruption in the accumulation of sedimentary rock due to erosion or nondeposition and crosscutting dikes intrusions of igneous rock that burrow through cracks in the original structures of surrounding rock. These field relationships, combined with the isotopic age determinations of specific rocks, allow for some correlation between neighbouring regions. Likewise, they divide the Proterozoic Eon into the Paleoproterozoic 2. These definitions are based on isotopic age determinations.
James E. Breeding, Steven B. Shirey, and Douglas Ashbury. Since mining operations began in , it has produced over million carats of diamonds.
Lake Turkana has a geologic history that favored the preservation of fossils. Scientists suggest that the lake as it appears today has only been around for the past , years. The current environment around Lake Turkana is very dry.