What techniques have scientists used to determine the earth's age?

Answer 1

Answer: Radiometric dating

Without resorting to materials that aren't "terrestrial" in nature, we can easily go back to around 4 billion years for rock samples that are native. Here's how it works.

A supernova of some kind creates (by atomic fusion) elements heavier than iron. These elements cannot be created by "regular" fusion as part of stellar nucleosynthesis, but only in the supernova event. Among the trans-iron elements is uranium.

Gas, dust and debris in an area begin to be gravitationally attracted to each other and coalesce. A star and some planets form. One is the third planet from the star. The initial state of the planet is one of molten material. It cools over a long time and rocks form. The core remains molten. The rocks that form begin a "life" based on what is inside them. If they are reclaimed or "remelted" by vulcanism, they have lost their identity and, if set out on the surface of the earth, begin a new "life" based again on what is inside them.

As rocks form, some zirconium gets trapped in the rocks along with some silicon, some oxygen and a bit of uranium. The temperatures at which these rocks form prevents lead from being included. Crystals form. The rocks underwent transformation to become crystals of a mineral called zircon, which is ZrSiO4. But there is some uranium present when things are getting together, and it sneaks into the crystal during formation in the place of some of the zirconium atoms. The uranium is now locked up in a lead-free crystal with zirconium, silicon and oxygen. Zircon is stable, tough and chemical- and weather-resistant. A crystal can hang around for billions of years. Some do.

Uranium has a number of isotopes. All uranium has 92 protons, but the number of neutrons varies. All uranium is unstable; it is radioactive and will eventually decay. What it decays into varies, depending on the starting isotope. Half-lives vary, too. U-238 is the most common isotope of uranium, and it comprises over 99% of the stuff we find. So most of the uranium in that zircon crystal is 238U. The 238U decays with a half-life of 4.46 x 109 years (4.46 billion years). That's a long time. And it's very convenient for us.

The 238U decays (eventually) into lead, specifically 210Pb, which is stable. There are a number of intermediate decay products, but the chain is well understood and half-lives are accurately known. If a sample of 238U is sequestered in a tightly sealed container (like a zirconium crystal), it can be studied there and we can find out how much uranium is there, and, based on what is in there with it (those decay products), we can "look back" and figure out how long it has been in there. Nothing can have happened to this crystal to change the chronology sealed inside if the crystal is intact. This is the heart of uranium-lead dating. Dating things well over 4 billion years old with an accuracy of a few million years is very doable in the lab. It is a painstaking and tedious activity, but it is the bread and butter of some devoted folks. They spend all their lives honing their skills at this - and their skills are razor sharp.

We drag our equipment out into the field looking for zircon crystals. We must find them "in rock" and not lying around on the ground. But we can find some. When we do, we know these little guys have been like they are now for a long time. But how long? Back in the office, we apply our laboratory radiometric dating techniques (micro-beam analysis), and we can date zirconium crystal samples back to nearly 4 billion years with an accuracy of + or - a few million years (not a few tens of millions of years). Easily. And that's how we know the oldest samples of rock found on earth date back to almost 4 billion years. Moon rocks and some material from meteors date back even farther by up to another half a billion years. And that is the source of the 4.54 billion year figure that is so often quoted for the age of the earth.

None of these activities requires Star Trek technology, a magic wand or a leap of faith. The underlying physics is as clear and understandable as the sunrise or the change of the seasons is.

The earliest geological time scales simply used the order of rocks laid down in a sedimentary rock sequence (stratum) with the oldest at the bottom. However, a more powerful tool was the fossilised remains of ancient animals and plants within the rock strata. After Charles Darwin's publication Origin of Species(Darwin himself was also a geologist) in 1859, geologists realised that particular fossils were restricted to particular layers of rock. This built up the first generalised geological time scale.

Once formations and stratigraphic sequences were mapped around the world, sequences could be matched from the faunal successions. These sequences apply from the beginning of the Cambrian period, which contains the first evidence of macro-fossils. Fossil assemblages 'fingerprint' formations even though some species may range through several different formations. This feature allowed William Smith (an engineer and surveyor who worked in the coal mines of England in the late 1700s) to order the fossils he started to collect in south-eastern England in 1793. He noted that different formations contained different fossils and he could map one formation from another by the differences in the fossils. As he mapped across southern England, he drew up a stratigraphic succession of rocks although they appeared in different places at different levels.

By matching similar fossils in different regions throughout the world, correlations were built up over many years. Only when radioactive isotopes were developed in the early 1900s did stratigraphic correlations become less important as igneous and metamorphic rocks could be dated for the first time.

Answer 2

This age of the Earth has been determined primarily by using radiometric dating which measures residual radioactivity in very old rocks.

Geophysicists have determined that the Earth is between 4.5 and 4.6 billion years old.

Direct measurements are most reliable.

Scientist have direct measurements that show there is material on Earth at least 4.4 billion years old. The oldest material found on Earth is in the form of small crystals of a material called zircon (zirconium silicate ZrSiO4). Because they have some uranium-lead content, the radioactivity allows their date of formation to be measured. Zircon is present all over the world, often in sand, but particular sites have very old crystals and in Australia these were measured to be 4.4 billion years old. They even suggest that water was present when they were formed.

Analysis of the isotope concentrations of lead in the oldest known samples of the mineral galena on Earth indicate that the lead is 4.5-4.6 billion years old.

Consistency is a critical test.

Tests must be conducted and comparisons made to make sure that these numbers make sense. One can rightly ask if there are perhaps older rock that just have not yet been found. Since the material on Earth was formed from something, presumably a cloud of gas and dust. The age of Earth can not be older than everything else in the solar system. That is why many meteorites have been tested as well as material returned from the Moon missions. Meteorite show a spread of ages between 4.53 to 4.58 billion years, so that is taken to mean the initial formation of the solar system cover a similar period of time. Moon samples show dates with a maximum of around 4.4 and 4.5 billion years. Even the rare martian meteorites have been dated to around 4.5 billion years old.

The final check is the age of the Sun. That is harder, but some information is known by looking at all the stars of a similar character and comparing age with luminosity and mass. These studies put the age of the Sun in the same time frame of 4.5 billion years, but with less accuracy.

Conclusion:

From all data available, the Earth and Sun and planets all formed about 4.5-4.6 billion years ago.

By the carbon of meteor.

The best way to get a solid reading for Earth's age is to find the age of an untouched piece of continental granite crust. The oldest rocks on Earth are found in the middle of the continents, because they have not been recycled into the mantle as oceanic crust is, and they have not been weathered as rocks on the surface may be. Scientists may use radiometric dating on these rocks.

The earth was formed at the same time as the rest of the solar system. Meteorites that have landed on earth and been carbon dated, consistently show an age of 4.3 to 4.5 billion years, so by extrapolation, that is also when the earth was formed. No rocks that old have been found in earth's crust, nor should they be expected to, as what we call the "surface" of the earth has been reformed several times since the planets birth by volcanic and tectonic activity.

Relative Dating

They determine the age of the earth by radioactive dating of the oldest rocks on our Earth, as well as by the stars.

It is noted that the age of our Earth by the above methods is consistent with the age of our solar system, based on the age of rocks in meteors and asteroids

Scientist can determine the age of the Earth by looking at different rocks. When we look at rocks we can see the effects of having oxygen in the atmosphere how long we have had this oxygen in the atmosphere and from here we can estimate how long from the big bang for the earth to cool down and then to form an atmosphere.

They determine the age of the earth by radioactive dating of the oldest rocks on our Earth, as well as by the stars.

It is noted that the age of our Earth by the above methods is consistent with the age of our solar system, based on the age of rocks in meteors and asteroids.

By the age of certain rocks. The oldest rock recorded was about 4.9 BILLION years

Answer 3

The lowest layer of rock or of a structure would be known as the oldest. The highest layer is then known as the newest/youngest. Scientists can't exactly determine the age of a rock but they can determine which layer is oldest and youngest, and then try to determine the age of the ones in the middle off of the basic observation.

Answer 4

by the amount of layers the one that is closest to the ground we walk on today is the oldest one

Answer 5

You could read The Bible, or you could believe in science. In the Bible, earths only a around 6,000 years old. Science says it's 4.5 billion years old. No one exactly knows for sure.