how do scientists estimate the age of the earth?

Question

what methods are used and which would be the most accurate/reliable method
thx

Answer 1

That's an interesting question with a complex answer.

First of all, we must understand that it is not possible to determine the exact age of the Earth directly from rocks because the oldest rocks have been recycled and destroyed by the process of plate tectonics - faulting, igneous events, metamorphism, erosion etc. countless times.

The ages of Earth and Moon rocks and of meteorites are measured by the decay of long-lived radioactive isotopes of elements that occur naturally in rocks and minerals and that decay with half lives of 700 million to more than 100 billion years to stable isotopes of other elements. These dating techniques, which are firmly grounded in physics and are known collectively as radiometric dating, are used to measure the last time that the rock being dated was either melted or disturbed sufficiently to rehomogenize its radioactive elements.

The oldest rocks on Earth found so far are the Acasta Gneisses in northwestern Canada near Great Slave Lake (4.03 Ga) and the Isua Supracrustal rocks in West Greenland (3.7 to 3.8 Ga), but well-studied rocks nearly as old are also found in the Minnesota River Valley and northern Michigan (3.5-3.7 billion years), in Swaziland (3.4-3.5 billion years), and in Western Australia (3.4-3.6 billion years). These ancient rocks have been dated by a number of radiometric dating methods and the consistency of the results give scientists confidence that the ages are correct to within a few percent.

Dating individual rocks doesn't give us the right answer either. Considering the Earth and meteorites as part of the same evolving system in which the isotopic composition of lead, specifically the ratio of lead-207 to lead-206 changes over time owing to the decay of radioactive uranium-235 and uranium-238, respectively, gives us a much better estimate. Scientists have used this approach to determine the time required for the isotopes in the Earth's oldest lead ores, of which there are only a few, to evolve from its primordial composition, as measured in uranium-free phases of iron meteorites, to its compositions at the time these lead ores separated from their mantle reservoirs. These calculations result in an age for the Earth and meteorites, and hence the Solar System, of 4.54 billion years with an uncertainty of less than 1 percent. To be precise, this age represents the last time that lead isotopes were homogeneous througout the inner Solar System and the time that lead and uranium was incorporated into the solid bodies of the Solar System.

The age of 4.54 billion years found for the Solar System and Earth is consistent with current calculations of 11 to 13 billion years for the age of the Milky Way Galaxy (based on the stage of evolution of globular cluster stars) and the age of 10 to 15 billion years for the age of the Universe (based on the recession of distant galaxies).

Some other answers have suggested that radiocarbon dating can be used to estimate the Earth's age. The half-life of radioactive carbon (C-14) is 5730 years - way too short to date anything beyond about 50,000 years, so carbon dating is NOT used to measure the age of the earth. Radiocarbon dating also can not be used to date most fossils, as they are usually more than 50,000 years old and they have been completely replaced by other minerals, so there's not even any carbon to date.

Answer 2

Estimated Age Of The Earth

Answer 3

Erosion. observation shows that erosion takes place at about 1 ft. every 5,000 years. Knowing this method, we can estimate the age of rock formations like the Grand Canyon. If the Canyon started out flat, it would take 30,000,000 years for the Colorado river to erode 600 ft of the Grand Canyon. Sedimentation. Another method used is to measure the rate at which sediment is deposited. Scientists think it takes between 500 and 10,000 years to deposit 1 foot of sediment. This method is not as accurate as the erosion method. Salinity of the oceans. Some geologists try to measure the age of the earth by the amount of salt in the ocean. First they need to find out how much salt is in the oceans. Then they find out how much salt rivers carry into the oceans each year. By comparing how much salt there is in the oceans now to how much is carried in by rivers each year, scientists can estimate the age of the oceans. Radioactive method.. One of the methods used is to study the uranium in igneous and metamorphic rocks. Uranium is a mildly radioactive substance that breaks down very slowly to form other elements and eventually lead. Uranium breaks down at a slow and steady pace which cannot be altered by temperature or pressure. Scientists calculate that it takes about 5 billion years for a half of a piece of uranium to become lead. By looking at different rocks and comparing the amount of uranium still in the rock to the amount of lead that has been formed, they can measure the age of the earth. Using this method, scientists have determined that the earth is 4-5 billion years old. Carbon-14 dating. All organic life forms have some amount of carbon-14 in them. When they die, no more carbon-14 is produced but instead the carbon-14 begins to slowly break down. Scientists think it takes 5,600 years for half of a piece of carbon-14 to break down. The fossil remains of creatures that had carbon-14 in them are found in sedimentary rock. By comparing the amount of carbon-14 in a rock to the amount of other substances that have been formed as a result of the breaking down of the carbon-14, scientists can date the rock. Carbon-14 dating is used to find the age of rocks up to 15,000 years old and the radioactive method is used for older rocks.

Answer 4

Radiometric dating is most comonly used. However, while Carbon-14 is a form, its half life is far too short. Some radioactive isotopes used along with the half lives associated are:

Potassium K-40: 1,280,000,000 yr
Rubidium Rb-87: 500,000,000,000 yr
Thorium Th-232: 14,100,000,000 yr
Uranium U-238: 4,510,000,000 yr
Uranium U-235: 710,000,000 yr


C-14 is generally used for fossils, not rocks

Answer 5

Uranium 238 to Lead 206 decay. It has a half life of about 4.5 billion years. We date meteorites, which are thought to be the same age as Earth.

Carbon 14 only has a half life of ~ 5730 years. It cannot be used to date Earth. Some of you guys fell asleep in Earth Science.

Answer 6

.rocks? i watched a movie based on *earth story.* they said to calculate / estimate the age of the earth is by measuring the rocks, break them down into bits and pieces. on the rocks you'll notice some patterns. those are regarding the earth's formation / weather. i.e. the rock is rough with up and down patterns produced millions of years ago due to the river which washed it away.

Answer 7

I believe carbon dating is the main way. Every fossil that is dug up is generally carbon dated to see what era the animal lived. It's also done with trees and fossils of trees. I believe they can do it with coal, oil and diamonds too since it takes many years for these natural resources to form and the different stages they transform in to along the way. I was in the army for many years. I spent 6 months in Egypt and visited St. Katherine's Monastery. It's on top of Mount Sinai. I saw the original "burning bush and grabbed a couple of leaves off of it and brought them home. They're in our family bible now. The bush is no longer a bush. It's a full grown tree and it's the only thing that will grow on that mountain top. It's been carbon dated and it actually does date back to then. It's guarded by the Monks in the monastery. It's got a concrete wall built around it with a fence on top of that even. I waited when nobody was looking and jumped up and snatched a couple of leaves. We were told absolutely not to touch it but I just had to! lol I also brought back 2 rocks from the very site where the Ten Commandments were burned out of the rock. There's a concrete wall built around that area with a window with bars in it so you can look in and see but you can't enter.

Answer 8

usage of radio carbon dating will be the most accurate to estimate the earth age

Answer 9

i think they pull it out of thin air. Since they think they are so bright, they go with a theory and present it as fact. It's really all a bunch of crap.

Answer 10

heat of the core of the earth