They don't.
Carbon-14 has a short half-life and is normally only used by archaeologists or anyone working on sediments less than 50,000 years old. It becomes much less accurate after 40,000 years.
Scientists used many different isotopes for dating rocks in Radiometric Dating, uranium/lead, potassium/argon and others are used. The half-life in some of these isotopes is measured in millions or billions of years.
It is not used for "carbon dating". Both U-238, and C-14 (radiocarbon, for carbon dating) are used to estimate the age of certain types of matter. These atoms decay, and from the amount of atoms remaining, an estimate of the age can be made.
Yes, see for details at: http://en.wikipedia.org/wiki/Uranium-lead_dating.
Uranium-238's decay product uranium 238 has a halflife of 246,000 years and so is useful for determining the age of sediments that are between 100,000 years and 1,200,000 years in age.
It isn't Carbon is used to measure the age of rocks.
Uranium 235 and uranium 238 are used in radiometric methods for dating of geological samples.
Isotopes Uranium 235 and uranium 238 are only natural isotopes of the element uranium.
Uranium-235 is not added to natural uranium, it is extracted from natural uranium by a process called enrichment.
Uranium 235 is a fissile material under thermal neutrons: - uranium 235 is used as a nuclear fuel in nuclear energetic reactors - uranium 235 can be used in nuclear bombs
Uranium and Plutonium
Uranium enriched with isotope 235 to approx 4 percent (natural U is 0.7 percent 235)
There are a few ways. First they use uranium 235 to date the oldest rocks. U 235 is radioactive so it has a half life that can be meaured.
That is the main use, to fuel nuclear power plants
Uranium-235 is an isotope of uranium making up about 0.72% of natural uranium.
U from uranium235U and 238U (recommended); also possible U-235 and U-238 or uranium-235 and uranium-238.
Approx. 0,7 % uranium 235 in natural uranium.
Isotopes Uranium 235 and uranium 238 are only natural isotopes of the element uranium.
Uranium-235 is not added to natural uranium, it is extracted from natural uranium by a process called enrichment.
Uranium-235 in combination with Uranium-238, enriched from natural levels of about 0.7% U-235 to about 5% U-235. There are other configurations, but this is the most common.
Uranium 235 is a fissile material under thermal neutrons: - uranium 235 is used as a nuclear fuel in nuclear energetic reactors - uranium 235 can be used in nuclear bombs
Uranium and Plutonium
Uranium enriched with isotope 235 to approx 4 percent (natural U is 0.7 percent 235)
Uranium dating methods were not used for fossils dating.