We have lots of techniques for getting the rough age of the Earth, and we have a handful of techniques for getting a detailed age. The latter fall under radioactive dating methods, and they are very accurate; we can measure with incredible precision the decay rates of some elements, and these form an almost literal ticking clock that can be read.
The Earth is 4.567 billion years old, plus/minus a small fraction of that. The thing is, finding intact rocks close to that age is hard. The Earth is active, with rocks getting subducted deep into the crust (and below), new rocks forming, erosion weathering them into dust, and so on.
So it’s pretty amazing that in Quebec, rocks have been found that are about 4.3 billion years old. They were discovered in the Nuvvuagittuq greenstone belt of northern Quebec, and the age was determined looking at ratios of isotopes of the elements samarium and neodymium.
These rocks date back to the time that the Earth’s crust was separating from the mantle, and even predate the time of heavy bombardment, when the Earth was pummeled by asteroid and comet impacts. The rocks were formed well after the impact that formed the Moon however, which happened less than 100 million years after the Earth itself formed.
I’ll add that small grains of minerals have been found that date back 4.3 billion years as well, but this is the first time extant rocks have been discovered. Science magazine has the full story (subscription required).
On a personal note, a few months ago I was giving a talk in Canada, and we visited the Ontario Science Centre. They had a timeline of the Earth laid out down a corridor, with rocks representing the various ages. That fellow on the left is a chunk of gneiss dated to be 4 billion years old, one of the oldest known rocks (I think it was the oldest known when it was found). It was sitting out there, so anyone could touch it. I am not mystical in any sense, but there was something very cool about touching the rock, actually contacting it physically. Monkey instincts, I guess, using our hands and fingers.
The funny thing is, you’d walk right past it if you saw it in the dirt. It would look like an ordinary, if rather pretty, chunk of stone. But our other good monkey instincts are curiosity, and the ability to examine things, figure out how they work, why they exist. Some scientists somewhere studied geology, others studied radioactivity, others investigated how the Earth’s surface formed. Together, these remote cousins (gneisses?) found all the clues we needed to put together the history of this rock, the Earth’s surface, and the Earth itself.
If you want to believe the Earth is 6000 years old, then you have that right. But you are one of the blind men feeling the tail of an elephant and claiming it’s a rope. You’re missing the big picture, and in this case, it’s a tapestry far richer, more satisfying, and more beautiful than you can know.
Tip o’ the gelogist’s hammer to Philippe Hamel and to Fark, which gave this story this marvelous headline: "6,000 year-old rocks found in Quebec." Credit for the first picture:Credit: Jonathan O’Neil/McGill Univ. via Science magazine. Second picture taken by me.
September 26th, 2008 at 11:49 am
Yeah! The Great One has mentionned me. Let me bask in the glow.
Ok, the 15 minutes are over…
September 26th, 2008 at 12:06 pm
So, my question would be “how do you pick what rocks to test?”
If the really ancient rocks look like the not-so-ancient-but-older-than-me rocks how do you decide which rocks you should bother to lug back to the lab. It’s clearly not as simple as “LOOK! Pull the car over, Margaret! That’s the oldest rock I’ve ever seen!”
September 26th, 2008 at 12:10 pm
Awesome. But please ‘god’ change the ‘then’ to ‘than’. Thank you.
September 26th, 2008 at 12:14 pm
I wonder what Ray unComfort thinks of this.
September 26th, 2008 at 12:15 pm
I read somewhere that the Earth & moon were once one & some cosmic collision separated the two early on. Shortly after that the Earth (post-collision) was pretty toasty warm, even liquid. If true, that would suggest if the Earth’s oldest “living” rock could only date to that time.
How does the “Rock of Ages” compare to the stuff retrieved from the moon (Luna)?
September 26th, 2008 at 12:17 pm
BA:
Sort of like touching the Moon rock on display at the Smithsonian, I suppose?
September 26th, 2008 at 12:20 pm
I love the Science Centre, but I haven’t been there in years…
September 26th, 2008 at 12:33 pm
@Ken B:
\>Sort of like touching the Moon rock on display at the Smithsonian, I suppose?
I’ve done that. Had to change my definition of the word ‘awestruck’ afterwards. There’s just no way to describe that experierence without using terms that sound nearly identical to religious reverence. I felt the same way the first time I saw Saturn or Jupiter through my own backyard telescope.
Sadly, that kind of language, when applied to moments of personal significance regarding nature or science, is a large part of the reason that creationists claim that science and materialism is as much a matter of ‘faith’ and ‘worldview’ as religious belief is. Let them play their silly semantic games – I refuse to let them stop me from sharing the wonder, the majesty and the awe of science and natural phenomena.
September 26th, 2008 at 12:35 pm
It is also like touching a Marsian meteorite rock, which I have done in my astro club meeting, so I know how you feel like. By the way, is there a theoretical basis on the fact that the radioactive dating is reliable other than the consistent results the rocks give when one dates it? I am just curious.
September 26th, 2008 at 12:38 pm
It is entirely too sad that some people will close their eyes to some of the most beautiful and awe inspiring things.. in favor of something they cannot see.
Don’t they realize, even if there is a god, that by supposing how this was all done, they’re basically telling the supreme being how it should / did do its job?
The world is an amazing place. The universe, doubly so.
September 26th, 2008 at 12:44 pm
Gneiss pun!
September 26th, 2008 at 12:54 pm
Ken B,
I’ve also touched the “moon rock” at the Smithsonian. Exactly how we do know its really a moon rock? Could be any old piece of granite/basalt/whatever with a nice plague for all we know.
September 26th, 2008 at 12:56 pm
Following up on IBY’s question, how do we know if a rock, with common elements that can be found on Earth, is originally from Earth or from a meteorite that fell to Earth? Look for rare elemtents in the rocks? I’m sure that would narrow it down, but is there a more conclusive method?
September 26th, 2008 at 1:28 pm
I subjected myself to a cerationist lecture at our local university (UNBC, Prince George, BC, Canada). His hypothesis was that, aside from the YEC stances of the common 600 year old earth, etc, geneticists were purposely misrepresenting facts and giving us false material. When we probed him to answer for geological evidence of a more aged earth, and all he replied with was “well, my molecular work says humans are 6000 years old, thus Earth must also be that old”. Full stop.
I, and a few others, kept him going with ~2 hours of questions, but he never wavered from his point – any evidence we presented, or logical fallicies suggested were ignored. Flat out ignored.
“This is my story and im sticking to it” YEC mentality!!
It was Dr. K. Anderson from the Creationist Institute..goolge him if yee like.
-T
September 26th, 2008 at 1:29 pm
There’s a chance you may have touched older – who knows how old some meteorites really are? They might have wandered in from outside the solar system.
September 26th, 2008 at 1:29 pm
Sorry, first line should have read “the YEC stance of the common 6000 year old earth”
sorry for an error of such magnitude…
September 26th, 2008 at 1:40 pm
Well, 600 or 6000, they’re equally stupid. I don’t think an apology is needed.
September 26th, 2008 at 1:57 pm
I’m glad that Phil told us it was a chunk of gneiss. I would have taken it for granite . . .
September 26th, 2008 at 2:07 pm
“If you want to believe the Earth is 6000 years old, then you have that right.”
I smell a quote mine!
September 26th, 2008 at 2:20 pm
>These rocks date back to the time that the Earth’s crust was separating from the mantle, and even predate the time of heavy bombardment, when the Earth was pummeled by asteroid and comet impacts. The rocks were formed well after the impact that formed the Moon however, which happened less than 100 million years after the Earth itself formed.
OK, I’ve always wondered this, so I have to ask. How do we know how old the Earth is? My understanding was that it’s from rock finds like this, and dating the moon rocks which give the same answer. But… If some cataclysmic collision created the moon from the collision of Earth and another planet, wouldn’t all the date markers be reset? Like the carbon ratios are continuiously reset in living creatures until they die? And obviously the Moon would be the same age, then, right? So the Earth could be much older, and just got a face lift of sorts by the moon collision. What’s wrong with that logic?
September 26th, 2008 at 2:33 pm
Gneiss!
September 26th, 2008 at 2:39 pm
Ray:
I guess it’s just a matter of faith.
September 26th, 2008 at 2:50 pm
That’s actually a pretty good point. It’s like trying to determine the age of a house that’s remodeled every few years. But let’s say you happen to find scraps scattered on the grounds. The oldest scraps should give some idea of the age of the house.
In the same way we can get an idea of the age of the Earth by the building scraps – meteorites. These left-overs from the time the planets condensed out of the accretion disk can give us an idea of just when all this happened. So meteorites were used to determine the age of the earth through radiometric dating.
Radiometric dating of moon rocks agrees with the estimate from meteorites. It’s a little younger than the meteorites, but not terribly so. Then there’s the microscopic remnants found in Australia, if I recall correctly – and this newly dated slab of rock in Quebec.
September 26th, 2008 at 2:59 pm
That just rocks, it just demostrates the rift between the YEC and science.
September 26th, 2008 at 3:27 pm
How big is the rock in the picture? It’s hard to get a sense of scale. It almost looks like you could use more than your fingers to experience that bad boy. It looks big enough to sit on! I’m guessing that is just a forced perspective view though.
September 26th, 2008 at 3:31 pm
Gneiss sounds like “nice”, not “niece”, but gneiss try.
Can you really say the earth was formed before the impact that created the moon? Surely without that impact, the composition of this planet would be different. I’d think that impact was a key event in the formation of this planet.
September 26th, 2008 at 3:38 pm
AFAIU one can use self-calibrating isochron dating.
@ Kevin, Ray, Tony, Lee:
Don’t forget isotope balances.
September 26th, 2008 at 4:42 pm
WOW!!!! That rock is almost as old as John McCain!!
September 26th, 2008 at 4:49 pm
I love how they have metal pipes holding the rock in place. Are they afraid someone will steal it?
September 26th, 2008 at 4:57 pm
This must be a geologist’s dream; finding the oldest rocks ever on Earth!
I can imagine how much mileage Apollo moon hoax believers will get from this, since a distinction between Earth rocks and moon rocks is that rocks from the moon show a greater age than rocks on Earth.
September 26th, 2008 at 6:20 pm
Even if this were true (and as Torbjörn says, it isn’t), we have other lines of evidence for the age of the solar system as a whole, which constrain the age of the earth under any reasonable assumptions. We have estimates for the age of the sun which depend on quite different reasoning, but agree very well with the planets forming shortly after the sun. Furthermore, we can see solar systems in various stages of formation, so we know are ideas aren’t completely out of whack (although there are plenty of puzzles and surprises!)
Of course, when creationists see the E word in “stellar evolution” they reject the whole field. Did you ever see a star turn into a cat ? I DON’T THINK SO!
September 26th, 2008 at 6:26 pm
@ Reed they it call stellar intelligent design.
September 26th, 2008 at 8:41 pm
I had a similar experience last summer. We were visiting my mother-in-law in southern Arizona and went on an afternoon trip to the Sonoran Desert Museum outside of Tucson. They had a rock there that the sign said was from the early formation of the solar system, and there was a hole in the box holding it so that you could reach in a touch it. Way cool!
September 26th, 2008 at 11:29 pm
This reminds me of a poem i wrote when I was in 8th grade. “Ode to a rock”
September 27th, 2008 at 12:34 am
[...] 4.28 billion-year-old rock! – I can’t wait to tell my friends. They don’t have a rock this old. IT’S THE OLDEST ROCK EVER! It’s like John McCain old! Picture the length of time it takes to watch the theatrical version of just one of the Lord of the Ring movies, and that’s how friggin’ old this thing is! PZ Myers calculates that means Ken Ham is wrong by a factor of over 713,000. This is also covered on Science Daily. [...]
September 27th, 2008 at 9:11 am
Ray asked: “Exactly how we do know its really a moon rock? Could be any old piece of granite/basalt/whatever with a nice plague for all we know.”
Moon rocks have certain characteristics which make them noticeably different from Earth rocks, at least for geologists. For examples: they lack water (all Earth rocks, even those spat from volcanoes, contain water bound into their chemical structure); they’ve been subject to no weathering by air or water; and their exposed surfaces show “zap pits” – tiny craters caused by the impact of dust particles at several kilometres per second.
September 27th, 2008 at 9:21 am
I presume that we’ve pretty much done all the research on that rock that we think we can. Doesn’t having people handle it at random potentially compromise geological data that can be mined from it? Or, do we just split it open and test the inside, which hasn’t been handled?
September 27th, 2008 at 10:05 am
Hey, folks read up on the Apollo missions sometime. You’ll see that the rocks from the Moon have been spared for public display because they’ve been scanned already, and/or have characteristics identical, so far as can be measured, to other rocks still in the lab.
Count the years. It’s been awhile.
One of the minerals brought back is now called “armalcolite”, named for Armstrong-Aldrin-Collins, who brought it back. It doesn’t occur on Earth.
Those of you with dating problems – sorry, not that kind – can actually get the info from a practicing Christian who knows when to read his instruments. See “Radiometric Dating – a Christian View”. It’s remarkably free of dogma.
You can also go find a copy of Nuclides and Isotopes, by GE Nuclear Energy. Your library might have one.
This stuff is studied so intently I don’t have the words to explain it.
September 27th, 2008 at 1:38 pm
Um…I know that around the Canadian Shield there is some pretty old out croppings of rock…but I’m curious to know how this thing survided all these years intact with very little erosion/contamination/etc. It must been in a real shady spot.
September 27th, 2008 at 3:42 pm
Utakata, no, it isn’t a shady spot. It survived 4.whatever billion years of erosion and glaciation. What you are seeing when you visit the Pre-Cambrian Shield is the bones of the earth. When you walk on the Shield you are walking on what once was far inside mountains.
September 27th, 2008 at 5:42 pm
I must say that claiming a 600y earth really is a whole level of nutjob greater than a 6000y earth. There is extensive written documentation of historical events older than 600y, but for 6000y I’m not aware of much, so the evidence is primarily archeological. That means you’d have to deny a whole additional level of evidence to claim a 600y earth. An even higher level of reality denial would be to claim a 60y earth, where one would have to disregard recorded video and audio evidence.
September 27th, 2008 at 10:27 pm
Thanks, Mr. Grizzly…that sorta makes things a little more clear on what was otherwise a little too astronomically mind boggling for me.
So that makes more sense now…it was cocooned not shaded.
September 29th, 2008 at 5:17 am
“This must be a geologist’s dream; finding the oldest rocks ever on Earth!”
Yeah, but imagine how he felt the day after.
“What did you do yesterday?”
“I found the oldest rock on Earth!”
“Nice! What’re you going to do today?”
“Um… “