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Name: Jorge
Status: student
Grade: 9-12
Country: Mexico
Date: Winter 2011-2012


Question:
What the oldest rock ever dated? Earth is supposed to have material of two previous generations of stars that died in the form of a supernova. If the solar system is about 4.5 billion years old, could we find rocks from before that time, say 8 billion years old?



Replies:
Presumably there are rocks older than the nominal age of the Earth (~4.3 billion years), since the age of the Universe that we observe is ~13.6 billion years.

The ages of the Sun and the Earth are about the same ( 4.5 billion years ). There are other star/planet systems that are older, as determined by their Doppler shift. Now, some rock escaping one of these exoplanets could exceed that age of the Earth/Sun. If such a rock were to wander around for some billions of years and then crash into the Earth, its age would exceed that of the Earth/Sun.

Should we capture such a rock, and do the appropriate isotope dating to confirm the age, I see no reason why that violates any laws of Nature.

Vince Calder


Jorge

Go to http://www.google.com

And search for Oldest Rock.

My favorite source is Wikipedia at:

http://en.wikipedia.org/wiki/Oldest_dated_rocks

"In 1999, the oldest known rock on Earth was dated to 4.031 ± 0.003 billion years, and is part of the Acasta Gneiss of the Slave craton in northwestern Canada."

and

"Some of the oldest surface rock can be found in the Canadian Shield, Australia, Africa and in other more specific places around the world. The ages of these felsic rocks are generally between 2.5 and 3.8 billion years."

Here is an article from Penn State University that includes a picture of the Canadian 4.3 Billion year-old rock.

http://www.windows2universe.org/headline_universe/olpa/oldrock_
26sept08.html

Since the age of the universe is estimated to be about 13.75 +/- Billion years (see http://en.wikipedia.org/wiki/Age_of_the_universe), it would be possible to find a meteorite rock that is older than 8 billion years old but it would not be native to planet earth which is about 4.6 Billion years old (http://en.wikibooks.org/wiki/General_Astronomy/Earth%27s_Early_Years).

Sincere regards,
Mike Stewart


Jorge,

Since the age of rocks depend on that particular rock not being melted, eroded, or in some way separated (rocks are dated by the kind of minerals and radioactive atoms that are near each other), it is impossible to find rocks that are older than the last time the current Earth formed. If in fact, the solar system has experienced periods of disintegration (as caused by a supernova) then things got atomized. While atoms survive such events, rocks don't. When Earth coalesced out of the gases of the explosion, a new cycle of rock ages begin.

Thus, the oldest rocks that have been dated are about as old as the Earth.

Greg (Roberto Gregorius)
Canisius College


The oldest rock on earth is thought to be part of the Acasta Gneiss in northwestern Canada. It dates to 4.031 billion years plus or minus 3 million years. I doubt that we will find rock on earth that is very much older.

Because the Earth is geologically active, most all rocks have been re-melted or changes by heat and pressure. Meteorites have been dated slightly older, about 4.5 Billion years. Could there be older rocks on one of the inner planets (Mercury, Venus and Mars)? That might be possible if they did not undergo "Continental Drift". But that is yet to be seen.

R. W. "Mr. A." Avakian
Instructor


The above answers are all correct. It should be pointed out that the oldest rocks on Earth can be found at the root or base shield of each continent. The oldest rocks of each continent are found in these root areas where the continent began forming as the Earth colled from a molten mass. The rest of the continents grew from that area. The Canada gneiss mentioned above (pronounced "nice") seem to be the oldest.

Steve Sample



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