Tuesday, January 12, 2010

Answering Creationist Claims (Part 9b - Evidence for a 4.54 billion year old Earth through Radiometric Dating)

While I did explain radiometric dating in my previous Answering Creationist Claims post, I don’t think I’ve given any direct evidence for an old Earth (not the Universe, that’s a different topic), and I think it’s my job to present them here:

Evidence from Rocks of the Earth

The Oldest Zircon – 4.404 Billion Years Old

Why are zircons are loved by geologists so much? Firstly, zircons are all too common in the Earth’s crust. It occurs in igneous, metamorphic, and sedimentary rocks. Zircons are able to survive geologic processes such as transport, erosion, even metamorphism (recrystallization), are chemically inert and they have much to tell about the geologic processes that occurred in history. However, the greatest thing is that within this mineral are uranium and thorium, and thus can be dated by the extremely accurate Uranium-Lead dating method, fission track dating, and (U-Th)/He dating.

At Mt Narryer and Jack Hills in the Narryer Gneiss Terrane, Yilgarn Craton,
Western Australia, a 4.404 billion year old zircon grain have been found, about 130 million years older than the previous record. Stunning, indeed. What’s more, a high ratio of stable isotopes was calculated using the δ18O method (7.5 – 5.0%), and the magmatic oxygen isotope ratios of such range points toward the possibility that the the oceans may have formed 4.4 billion years ago, 100 millions years than previously expected! While this is still under debate within the scientific community, it nevertheless provides an exciting point of view.

4.404 byr year old zircon

Cathodoluminescence image of earth's oldest-known mineral (zircon grain - W74/2-36) with inset concordia plot showing the 4,404 billion year old region. Note the oscillatory zoning in the outer rim. Image by John W. Valley. © University of Wisconsin

The Oldest Rocks: The Acasta Gneiss Complex - 4.04 Billion Years Old/Nuvvuagittuq greenstone belt – 4.28 Billion Years Old

The Acasta Gneiss Complex is a rock outcrop located at Slave Province, Northwest Territories of Canada. Dated to be at about 4.04 billion years old in the Hadean period (informal), the Acasta Gneiss complex is the oldest exposed rock to date. A zircon dated 4.2 billion years old using mass spectrometry was also found within a 3.9 billion year granite rock, providing further evidence that the Acasta Gneiss Complex is the oldest rock to date.

Acasta Gneiss Complex

Close-up View of the Acasta Gneiss Complex

On September 25, 2008, researchers from McGill University, Carnegie Institution for Science and UQAM announced that a rock formation known as the Nuvvuagittuq greenstone belt, located on the eastern shore of Hudson Bay in Quebec may be older than the Acasta Gneiss Complex after all. Dated at 4.28 billion years old using the Samarium-Neodymium dating method, it is surely a great contender against the Acasta Gneiss Complex. However, Simon Wilde of the Institute for Geoscience Research in Australia said that:

On the weight of evidence from other studies in the area, I would still consider that 3.8 billion years is more likely the actual age of the rocks.

The Nuvvuagittuq greenstone belt (Dammit, why is it so hard to pronounce?)

Nevertheless, should overwhelming evidence arise for the 4.28 billion year old age of the Nuvvuagittuq greenstone belt, it would be plain awesome.

Evidence from Meteorites

Despite being so old, rocks and minerals still do not tell us when was the formation of the Earth. Why? Well, with the combined forces of geologic processes such as plate tectonics, weathering, eruptions and hydrothermal circulation destroyed most of the evidence available by mixing them and constantly resetting the point of closure of minerals. Thus, we have to look towards the fallen stars for an answer. But why meteorites? Firstly, meteorites are big pieces of rock without the dynamic geologic processes associated with the Earth; that is, they’re quite static, and the crusts have never been recycled. Secondly, it is only fair to assume that everything in the Solar System formed from the same molecular cloud, and the age of meteorites give hints to the true age of the Earth.

Canyon Diablo Meteorite - 4.550 billion years (± 70 million years)

Around 50,000 years ago, the Canyon Diablo meteorite smashed into Arizona, creating the Meteor Crater/Barringer Crater. This meteorite is particularly special as it a big piece of a rare type of meteorite that contains sulphide minerals (particularly troilite, FeS), metallic nickel-iron alloys, plus silicate minerals.

In 1953, Clair Cameron Patterson dated the Canyon Diablo meteorite at 4.55 billion years old using Uranium-Lead dating, by measuring the amount of lead in the sulphide within the meteorite, and not surprisingly, it was found in much greater amounts than uranium, the parent nuclide. This date is supported by  almost 70 well-dated meteorites with ages of 4.4-4.6 billion years. These meteorites, which are fragments of asteroids and represent some of the most primitive material in the solar system, have been dated by 5 independent radiometric dating methods (got this info from the United States Department of the Interior).

Holsinger Meteortie

Holsinger Meteorite: the biggest recovered fragment of the Canyon Diablo meteorite.

Evidence from the Moon

That's one small step for man, one giant leap for mankind. – Neil Armstrong

I did not hear that word, and I assume that many of you never did too. Yet, when Apollo 11 landed on the Moon, it fulfilled the our ancestor’s dreams of meeting the Moon. During the subsequent Apollo missions and the Soviet' Union’s Luna missions, many moon rocks would be taken home for research (plus those that fell to Earth as meteorites), and they all point to one thing: the Solar System is, at the very least, 4.5 billion years old.

The rock samples from the Moon range from 3.16 billion years old for the basaltic samples derived from the lunar maria, and up to about 4.5 billion years old for rocks derived from the highlands. As there is has been zero plate tectonic activity and no atmosphere (no weathering), we can be confident that this represents a quite truthful age for the Solar System.

Genesis Rock

Genesis Rock: A sample of early lunar crust from around the time the Moon formed. Returned by the Apollo 15 mission.


Thus, as I have shown, the evidence for an old Earth through radiometric dating is simply overwhelming, and that’s not taking evidence from the cosmos, erosion, etc. into account. It's a wonder that YECs can look at all this evidence and still insist that the Earth is 6000 years old. *facepalm*

Creationism Demotivational


Simon A. Wilde, John W. Valley, William H. Peck & Colin M. Graham. (2001) Evidence from detrital zircons for the existence of continental crust and oceans on the Earth 4.4 Gyr ago. Nature.

Tsuyoshi Iizuka, Kenji Horie, Tsuyoshi Komiya, Shigenori Maruyama, Takafumi Hirata, Hiroshi Hidaka, and Brian F. Windley. (2006). 4.2 Ga zircon xenocryst in an Acasta gneiss from northwestern Canada: Evidence for early continental crust. Geology 2006;34;245-248. doi: 10.1130/G22124.1

Previous: Answering Creationist Claims (Part 9a – Deny The Age of the Earth and You Deny Science Itself)