I think all the craters are cool, I’ll start with that. I am very biased.
Impact craters occur on every planetary body in our Solar System, regardless of size. By studying impact craters and the meteorites that cause them, we can learn about the processes and geology that make up our entire Solar System.
This list contains some of my favorite craters on Earth.
1. Meteor Crater, AZ, US
The one who started it all.
Barringer Crater (commonly called Meteor Crater), is located near the town of Winslow on Route 66 in Arizona, US, and was the first confirmed extraterrestrial impact crater.
Meteor Crater is 1km wide and about 50,000 years old, making it “young”. We have known about the crater since the end of the 19th century, but there has been debate whether it is caused by an impact, or related to the nearby volcanic province.
It wasn’t until the 1960s when high-pressure quartz forms were identified in rocks, as well as meteorite fragments found nearby, that scientists could definitively say that it is a meteorite impact.
The crater is an area of active research. It is very well preserved, making it a great place to study impact cratering. Since the early days of Apollo, Meteor Crater has been used to train astronauts. This practice continues to this day, with Artemis scientists learning to navigate environments similar to those they will encounter on the moon, as well as studying geology.
Today you can visit the crater (the gift shop is great!) It’s a great addition to any trip to the Grand Canyon.
2. Chicxulub, Yucatan, Mexico
Dinosaur killer!
Perhaps the most famous meteorite impact on Earth is the one that left the Chicxulub impact structure on the Yucatán peninsula in Mexico. This 180 km wide crater is the second largest on Earth and was dated 66 million years ago – at the same time as the extinction of the dinosaurs.
For years geologists have searched for mass extinctions recorded in rocks around the world. It was only until the discovery of iridium, which is more abundant in meteorites than on Earth, that fragments fell into space.
The object that impacted the Earth was estimated to be 10km in diameter, traveling at 20km/s. It’s about 5 minutes from Sydney to Los Angeles.
It wasn’t just the dinosaurs that went extinct, however – it’s estimated that 75% of the world’s plant and animal species died out as a result of this event.
The result would have been an immediate disaster, and the consequences were felt for decades. There were huge tsunamis, and forests were burned around the world. The sun’s light would have been wiped out by the ash and gases, possibly for many years, triggering a global winter in which many species died out.
However, the crater system eventually became a deep biosphere as the planet became populated at the end of that long winter.
3. Vredefort, South Africa
It’s big.
Impact craters can be a source of economic resources. For example, an impact can concentrate metals that were there before the crater was formed,/
The final issue is the state of Vredefort’s structure in South Africa. It is estimated that more than a third of the world’s gold is mined from here.
The Vredefort impact crater is the largest confirmed crater on Earth and is about 2 billion years old. The original Crater was thought to be about 300km across, but it has grown much larger.
The impact exposed some of the oldest rocks in the world. It is one of the few places where you can see a complete geological record of the third part of the Earth’s history, with rocks from 2.1 to 3.5 billion years old.
When most people think of a crater, they think of a roughly circular depression, like Meteor Crater. But the craters can have different shapes and features – Vredefort has a complex shape and is known as the center of many types of activity. These basins form with very large impacts and can be seen in other groups of planets; Mare Orientale on the Moon is another example.
4. Tnorala (Gosses Bluff) crater, NT, Australia
Dreamtime stories.
Australia is home to the oldest living culture in the world, with evidence of people living on the continent for at least 65,000 years. It also has 30 craters, and these beautiful geological structures are often considered sacred places by the local population.
Gosse’s Bluff impact crater is known as Tnorala by the Western Arrernte people. Their dream-time stories of creation state that the crater was formed when a group of women danced across the sky as the Milky Way. During this dance, a mother kept her baby aside in its wooden cradle. The porter fell over the edge of the dance floor and fell to the ground where he was transformed into the shape of Tnorala’s round stones.
Today Tnorala is 4.5km wide and sits 150m above the surrounding desert, but when it first formed 142 million years ago, it was probably around 24km wide and was destroyed when time is running out.
Several other craters in Australia have Dreamtime songs and stories associated with them, such as the Henbury crater 120 kilometers south-east of Gosses Bluff, and is one of the rarest events ever seen by humans. The meteorite fell in what is now central Australia 4,700 years ago.
5. Nordlinger Ries, Germany
Diamonds and gems.
The Nördlinger Ries, also known as the Ries crater, is one I’ve been lucky enough to visit. It was formed about 14 million years ago and is about 24km wide. The town of Nördlingen is inside the crater, south of the center. If you climb the steeple of the church, you can see the edge of the procession.
This was the second crater shown to have an impact by the same team investigating Meteor Crater.
Also, the identification of a very high pressure type of quartz – coesite – holds the key. This grape was once found naturally only in rocks thought to have formed deep within the Earth, or in nuclear test explosions. There was no evidence of one at Nördlingen, which means that the coesite must have been formed by impact.
Many buildings in the city, including the church, were built using rocks formed by the impact. This includes a brecciated (literally – broken into small pieces) rock called suevite. This suevite is special because the pre-impact rocks in this part of Bavaria included a layer of graphite.
During the impact, the graphite was under very high pressure and temperature. This turned the graphite into millions of tiny diamonds spread across the city’s buildings.
The impact also hits the sandy layer of material near the surface, creating glassy green tektites. Tektites are molten glasses made from materials that are ejected from the atmosphere. They can often be found hundreds or thousands of kilometers from the original impact site.
In this case, they were found in Czechia near the Moldau River and are therefore called moldavites. Unlike Ries diamonds, moldavite occurs in specimens large enough to be used in jewelry as a semiprecious stone.
There are still more craters
The five craters above are different, and all can be considered unique. None of them have exhausted all the scientific questions we can ask.
Fortunately, there are still some craters that we can find on Earth. As satellite imagery becomes more readily available at higher resolutions, we are able to identify more patterns of influence in remote areas. Geologists could examine these and look for structures and chemical signatures of influence.
Every crater – no matter how old or hidden – has the potential to teach us something new about our planet, our Solar System, and the geological processes that shape it.
Helen Brand, Senior Beamline Specialist – Powder Diffraction, Australian Society for Nuclear Science and Technology.
This article is reprinted from The Conversation under a Creative Commons license. Read the first article.
