When we were going back to Phoenix from the Grand Canyon, we turned east in Flagstaff and took a 45 minutes detour to visit the Barringer Meteor Crater (a.k.a. Meteor Crater Natural Landmark). This is the most well-preserved meteor crater in the world and the first confirmed impact crater on Earth caused by an extraterrestrial collision.
The meteorite that created this crater 50,000 years ago is known as the Canyon Diablo meteorite. There are currently about twenty notable fragments of the meteorite, ranging from a few kilograms to over half a ton, and these are housed in museums and observatories around the world. The Canyon Diablo Meteorite also significantly contributed to calculating Earth’s age as a fundamental experiment sample of the lead-lead dating process (Pb-Pb isochron dating).
Both the crater and the meteorite have made significant marks in the history of human being’s understanding of the Earth and the universe. However, maybe due to its private land ownership, its remote location, or perhaps the stubbornness of rural American religious groups, it is somehow not a well-known landmark, and the number of visitors is relatively low.
Barringer Crater
We encountered several volcanic craters along I-40 on the way to the meteor crater. Since the Barringer Meteor Crater is located in a volcanic belt, it was thought to be a volcanic crater from its discovery in the late 19th century until the early 20th century. In 1903, entrepreneur and mining engineer Daniel Barringer proposed that the crater was caused by a massive iron meteorite impact and spent the following decades attempting to mine it, but did not find large quantities of iron meteorite as planned. Skepticism from other geologists towards his theory persisted until 1960, when impact quartz was discovered in the lower layers around the crater, dispelling the doubts.
Barringer Meteor Crater is currently privately owned. None of the national park or state park passes would work here. After buying tickets, we entered the visitor center right away and we could directly walk to the edge of the crater to overlook the entire site.
The Barringer Meteor Crater is 1.2km / 0.75mi in diameter and 170m/560ft deep, with the impact occurring approximately 50,000 years ago during the Pleistocene epoch. It looks like this on satellite maps:
The strata in this region were originally stacked in a neat, chronological order of sedimentary rock from bottom to top. However, the crater’s edge shows visible upward tilting, an inversion of the sedimentary sequence near the surface, and the presence of impact quartz (such as coesite and stishovite) which only forms under extremely high-pressure conditions. These features are similar to those found in craters created by nuclear explosions, distinguishing them from volcanic craters.
The visitor center offers detailed information about the meteor crater and the surrounding rock formations.
Through a telescope, we could see that the central part of the crater is fenced up. This area contains mining equipment and facilities left by Daniel Barringer over a hundred years ago, as he was convinced that there would be a significant amount of meteorite fragments beneath the crater.
Canyon Diablo Meteorite
The Canyon Diablo meteorite that created the Barringer Meteor Crater is an octahedrite. It is composed of over 90% iron, 7% nickel, and trace amounts of cobalt, gallium, and germanium. It is estimated that the original meteorite was about 50 meters in diameter, but most of it vaporized upon impact, leaving only a few fragments scattered around the crater.
The largest fragment, weighing 639kg / 1,400lbs, is housed in the visitor center of the crater, while others are found in museums and observatories around the world, including Christchurch’s Canterbury Museum, the French National Museum of Natural History, Berlin’s Archenhold Observatory, and the Griffith Observatory in Los Angeles.
I’ve had the fortune to see and touch the fragments at the Natural History Museum of Los Angeles and Griffith Observatory.
The larger fragments are definitely too heavy to lift, but at least people can touch them and feel some of the ‘energy’ from outer space. The 4kg / 9lbs piece at Griffith Observatory is the only one I was able to pick up directly. It feels quite dense.
Nebular hypothesis of the formation of the solar system and lead-lead dating
In 1956, Clair Patterson from Caltech used lead-lead dating on Canyon Diablo meteorite samples to determine Earth’s age as 4.55 ± 0.07 billion years.
The current nebular hypothesis suggests that all planets, moons, asteroids, and meteorites in the solar system evolved and formed from the dust surrounding the young Sun. Meteorites, with their simpler chemical composition and isolated status in space, retain their original isotope ratios, which enhances measurement accuracy. In contrast, Earth’s surface rocks have undergone extensive and complex magmatic and metamorphic processes, making direct dating challenging— it was until 2001 that scientists confirmed some 4.4 billion-year-old zircon in Western Australia.
Lead-lead dating is a derivative of uranium-lead dating. Lead has four isotopes: 204Pb, 206Pb, 207Pb, and 208Pb. 204 is not a decay product and thus has a constant amount, while 206 and 207 are decay products of uranium-238 (238U) and uranium-235 (235U) respectively, and increase over time. By plotting the 206Pb/204Pb and 207Pb/204Pb ratios of meteorite samples on an isochron, the age of the sample can be calculated. The 208Pb isotope, being a decay product of thorium, is not involved in the uranium-lead system. Specific quantitative calculations can be found online.
The end
For those interested in nature and science, visiting the Barringer Meteor Crater in Arizona is highly recommended!