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Through Radiometric (also known as Radioactive) dating.
They search for the decay of isotope solutions. By seeing how much decayed, they are able to calculate how long it took for that amount to decay. Meaning they are able to calculate how long ago they've been decaying from, and how old the rock is.
For sedimentary rocks age you check the fossils
By measuring the amount of Uranium contained within the specific rock/fossil. Uranium-238's Half-Life is about 4.47 billion years, So each 4.47 billion years, the amount of Uranium is reduced by half. If the accepted amount of Uranium for a time period is 25%, and the sample contains 12.5%, then it is twice as old as that time period. Scientists cannot use carbon dating on rocks because they were never living things, and did not inhale carbon-14 from the atmosphere.
the age of a arock can eb determinded by measn of a process called carbon dating. Depending on the amount of carbon present and the halp life period of carbon, th eage of amaterial can be determined.
They do it by using the law of superposition. This law states that younger rocks lie above older rocks in undisturbed rock sequences. And if they are not undisturbed then there might be other causes like tilting, folding, faults and intrusions.
scientists know that the youngest rocks are formed at the mid-ocean rift and the oldest rocks are farther out. hope this helps :)
looking at patterns
Sedimentary rocks contain bits of sediment, each much older than the rocks they form
The law of superposition states that the oldest strata in an undisturbed formation of rock are the oldest.
Carbon
Earth was too hot to have solid rocks at that time.
There are many, but the trilobite is considered an exceptional index fossil.
Scientists date sea-floor rocks by looking at patterns in the rocks, including magnetic patterns, and by looking at the geomagnetic reversal time scale.
Sedimentary rocks contain bits of sediment, each much older than the rocks they form
Because they want 2
See the links below.
The law of superposition states that the oldest strata in an undisturbed formation of rock are the oldest.
because is out of date and no one want s it any more and i think that people should not ask this question any more
DISGUST
Carbon
Radioactive materials decay at predictable rates
The rocks of "greenstone belts" some of which date to almost 4 billion years ago are the oldest intact rocks. Some individual zircon crystals found in much younger rocks date to 4.4 billion years ago.
The basic idea is to compare the abundance of a naturally occurring radioactive isotope within a material to the abundance of its decay products; it is known how fast the radioactive isotope decays.
By looking at a calender.