Posted on 02/09/2019 12:13:39 PM PST by ETL
Planet Earth doesn't have a birth certificate to record its formation, which means scientists spent hundreds of years struggling to determine the age of the planet. By dating the rocks in Earth's ever-changing crust, as well as the rocks in Earth's neighbors, such as the moon and visiting meteorites, scientists have calculated that Earth is 4.54 billion years old, with an error range of 50 million years.
Scientists have made several attempts to date the planet over the past 400 years. They've attempted to predict the age based on changing sea levels, the time it took for Earth or the sun to cool to present temperatures, and the salinity of the ocean. As the dating technology progressed, these methods proved unreliable; for instance, the rise and fall of the ocean was shown to be an ever-changing process rather than a gradually declining one.
And in another effort to calculate the age of the planet, scientists turned to the rocks that cover its surface. However, because plate tectonics constantly changes and revamps the crust, the first rocks have long since been recycled, melted down and reformed into new outcrops.
Scientists also must battle an issue called the Great Unconformity, which is where sedimentary layers of rock appear to be missing (at the Grand Canyon, for example, there's 1.2 billion years of rock that can't be found). There are multiple explanations for this uncomformity; in early 2019, one study suggested that a global ice age caused glaciers to grind into the rock, causing it to disintegrate. Plate tectonics then threw the crushed rock back into the interior of the Earth, removing the old evidence and turning it into new rock.
In the early 20th century, scientists refined the process of radiometric dating. Earlier research had shown that isotopes of some radioactive elements decay into other elements at a predictable rate. By examining the existing elements, scientists can calculate the initial quantity of a radioactive element, and thus how long it took for the elements to decay, allowing them to determine the age of the rock.
The oldest rocks on Earth found to date are the Acasta Gneiss in northwestern Canada near the Great Slave Lake, which are 4.03 billion years old. But rocks older than 3.5 billion years can be found on all continents. Greenland boasts the Isua supracrustal rocks (3.7 to 3.8 billion years old), while rocks in Swaziland are 3.4 billion to 3.5 billion years. Samples in Western Australia run 3.4 billion to 3.6 billion years old.
Research groups in Australia found the oldest mineral grains on Earth. These tiny zirconium silicate crystals have ages that reach 4.3 billion years, making them the oldest materials found on Earth so far. Their source rocks have not yet been found.
The rocks and zircons set a lower limit on the age of Earth of 4.3 billion years, because the planet itself must be older than anything that lies on its surface.
When life arose is still under debate, especially because some early fossils can appear as natural rock forms. Some of the earliest forms of life have been found in Western Australia, as announced in a 2018 study; the researchers found tiny filaments in 3.4-billion-year-old rocks that could be fossils. Other studies suggest that life originated even earlier. Hematite tubes in volcanic rock in Quebec could have included microbes between 3.77 and 4.29 billion years ago. Researchers looking at rocks in southwestern Greenland also saw cone-like structures that could have surrounded microbial colonies some 3.7 billion years ago.
Meet the neighbors
In an effort to further refine the age of Earth, scientists began to look outward. The material that formed the solar system was a cloud of dust and gas that surrounded the young sun. Gravitational interactions coalesced this material into the planets and moons at about the same time. By studying other bodies in the solar system, scientists are able to find out more about the early history of the planet.
The nearest body to Earth, the moon, doesn't experience the resurfacing processes that occur across Earth's landscape. As such, rocks from early lunar history still sit on the surface of the moon. Samples returned from the Apollo and Luna missions revealed ages between 4.4 billion and 4.5 billion years, helping to constrain the age of Earth. How the moon formed is a matter of debate; while the dominant theory suggests a Mars-size object crashed into Earth and the fragments eventually coalesced into the moon, other theories suggest that the moon formed before Earth.
In addition to the large bodies of the solar system, scientists have studied smaller rocky visitors that have fallen to Earth. Meteorites spring from a variety of sources. Some are cast off from other planets after violent collisions, while others are leftover chunks from the early solar system that never grew large enough to form a cohesive body.
Although no rocks have been deliberately returned from Mars, samples exist in the form of meteorites that fell to Earth long ago, allowing scientists to make approximations about the age of rocks on the Red Planet. Some of these samples have been dated to 4.5 billion years old, supporting other calculations of the date of early planetary formation.
More than 70 meteorites that have fallen to Earth have had their ages calculated by radiometric dating. The oldest of these are between 4.4 billion and 4.5 billion years old.
Fifty thousand years ago, a rock hurled down from space to form Meteor Crater in Arizona. Shards of that asteroid have been collected from the crater rim and named for the nearby Canyon Diablo. The Canyon Diablo meteorite is important because it represents a class of meteorites with components that allow for more precise dating.
In 1953, Clair Cameron Patterson, a renowned geochemist at the California Institute of Technology, measured ratios of lead isotopes in samples of the meteorite that put tight constraints on Earth's age. Samples of the meteorite show a spread from 4.53 billion to 4.58 billion years. Scientists interpret this range as the time it took for the solar system to evolve, a gradual event that took place over approximately 50 million years.
By using not only the rocks on Earth but also information gathered about the system that surrounds it, scientists have been able to place Earth's age at approximately 4.54 billion years. For comparison, the Milky Way galaxy that contains the solar system is approximately 13.2 billion years old, while the universe itself has been dated to 13.8 billion years.
Further reading:
This article was updated on Feb. 7, 2019, by Space.com contributor Elizabeth Howell.
A fist-size sample of the Acasta Gneisses, rocks in northwest Canada that are the oldest
known rocks on Earth. Credit: Mike Beauregard/Creative Commons.
Not as old as ‘nasty p-lousy”
The Acasta Gneiss is a tonalite gneiss in the Slave craton in Northwest Territories, Canada.
The rock body is exposed on an island about 300 kilometres north of Yellowknife.
The rock of the outcrop was metamorphosed 3.58 to 4.031 billion years ago and is the oldest known intact crustal fragment on Earth.[1]
First described in 1989, it was named for the nearby Acasta River east of Great Bear Lake.
The Acasta outcrop is found in a remote area of the [...] people land settlement.
It is the oldest known exposed rock in the world.
Contents:
1 Formation
2 Contention for record
3 Exhibit
4 See also
5 References
6 Bibliography
Formation
The metamorphic rock exposed in the outcrop was previously a granitoid that formed 4.2 billion years ago, an age based on radiometric dating of zircon crystals at 4.2 Ga.[2]
The Acasta Gneiss is important in establishing the early history of the continental crust.
Acasta Gneiss was formed in the Basin Groups unofficial period of the Hadean eon, which came before the Archean: see Timetable of the Precambrian.
Contention for record
In 2008 an age of 4.28 billion years was reported for an outcrop in the Nuvvuagittuq Greenstone Belt on the eastern shores of Hudson Bay, 40 kilometres south of Inukjuak, Quebec, Canada.[3]
However, the dating method used did not involve similar radiometric dating of zircon crystals and it remains somewhat contentious whether the reported date represents the age that the rock itself formed or a residual isotopic signature of older material that melted to form the rock.[4]
Mafic rocks from the Nuvvuagittuq Greenstone Belt have recorded isotopic compositions that can only be produced in the Hadean (i.e. older than 4 billion years ago) and the complete isotopic study of all the lithologies included in the Nuvvuagittuq Greenstone Belt suggests that it was formed nearly 4.4 billion years ago.[5]
“Radioisotopes and the Age of the Earth (RATE)
Scientists associated with the Institute for Creation Research
have finished a five-year research project known as RATE,
or Radioisotopes and the Age of the Earth.”
“How old are your rocks?”
Same age as me.
How old are your socks?
So old they’ve become holey relics.
Phobos is one of these moons (today, that is)
another place is the rings/moons of Saturn
I might have read this originally about Uranus and its 27 moons, but a quick check turned up no links to help jog my memory.
There's only one thing that could have prevented deposition of sedimentary layers for 1.2 billion years.
Tinfoil. Duct tape would have broken down too soon.
That, of course, leaves open the question of who removed the tinfoil several billion years ago.
I think my mom has some specimens.
“How old are your rocks?”
My rocks are the same age as me.
Sorry. Didn’t mean to plagiarize your post.
Does it really, really matter since we’re the ones that created “time”.
The RATE project concluded that nuclear decay rates were accelerated by a factor of around 500 million times currently measured rates during the Creation week and again during the Flood.
They have no solution to the problem that the heat created by this rate of decay would heat the Earth’s surface to over 22,000 degrees Celsius.
The process of planetary formation is a theory not a proven fact. IThat it looks right does not mean that it is right.
As for the time the zircons were formed 4+ billion years ago - there was an article years ago that postulated that the necessary conditions for there formation meant the Earth looked much as it does today - blue skies, large bodies of water etc.
Reference:
Myth of hellish Earth doused in water
Anna Salleh
ABC Science Online
Friday, 6 May 2005
There is a later article with the same tittle on the same site by a different author dated 2 years later which contains only a bit of the original - ABC self-censoring science even back then.
Nonsense. Presuppositions and “facts” unverifiable through experimentation running rampant. Nonsense, just unverifiable propaganda.
We measure time, I think, by segments of our choosing.
A billion here and a billion there, pretty soon you’re talking about some real time.
5.56mm
To the lefties i bet it feels like President Trump has been in office for a billion years. :)
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