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The most widely known form of radiometric dating is carbon-14 dating.
This is what archaeologists use to determine the age of human-made artifacts. The half-life of carbon-14 is only 5,730 years, so carbon-14 dating is only effective on samples that are less than 50,000 years old.
These were most likely driven by regular changes in Earth’s orbit and rotation known as the Milankovich Cycles that govern the seasonal timing and intensity of solar energy entering the atmosphere.
Other factors that may have contributed to the formation and cessation of ice ages are the amount of greenhouse gases (mainly carbon dioxide, methane, and water vapor) in Earth’s atmosphere, the extent of sea and land-based ice across the northern hemisphere, and shifts in patterns of wind and ocean currents.
We don’t really know why it happens, or even when it is likely to happen next, but every several hundred thousand years or so, the Earth’s magnetic field reverses. We know this, because when rocks are formed, they are indelibly marked with the normal or reverse polarity of their birth time, or chron.
Apart from being a geological curiosity, the constant toing-and-froing of the Earth’s polarity has proven extraordinarily useful in pin-pointing the geological ages of rocks.
This is perhaps no better illustrated than in the recent – and incredibly precise – dating of the Australopithecus sediba remains from South Africa.
The movement of the ice across the surface of the planet also scoured deep valleys, created extensive chains of hills known as moraines, and created extensive lakes, including the Great Lakes.
Understanding the onset and termination of glacial and interglacial cycles is a key part of efforts to understand how Earth’s climate system works and how it responds to changes and disruptions.