Scientists discover massive underwater crater that is 3x larger than the Grand Canyon
About 35 million years ago, an asteroid struck the ocean off the East Coast of North America, leaving behind a massive impact crater.
The location of the crater in Chesapeake Bay. It is now completely covered by younger sediments, but was discovered in the early 1990s by marine geophysical surveys and subsequent drilling. (CREDIT: Powars et al. 2015, Christoph Kersten / GEOMAR)
About 35 million years ago, an asteroid struck the ocean off the East Coast of North America, leaving behind a massive impact crater now buried beneath the Chesapeake Bay.
The collision unleashed devastating effects, including widespread fires, powerful earthquakes, molten glass droplets, an immense air blast, and a tsunami that reshaped the landscape of what is now Virginia and Maryland.
The impact created a crater approximately 25 miles in diameter, which has since been completely concealed by sediment. Though hidden, its existence was confirmed in the early 1990s through scientific drilling.
It remains the largest known impact crater in the United States and ranks as the 15th largest on Earth, highlighting the immense force of the ancient asteroid strike.
Beyond the crater itself, the asteroid impact ejected a vast amount of debris into the atmosphere. This material included tektites—natural glass formed from meteorite impacts—and zircon crystals that underwent intense shock from the explosion. These shocked minerals serve as key geological evidence of the impact’s intensity.
The scattered debris formed what is now called the "North American tektite strewn field," an expansive layer of ejecta that stretches across approximately 4 million square miles—about ten times the size of Texas. Some of the debris fell onto land, while much of it cooled rapidly upon contact with seawater and settled on the ocean floor, preserving a record of the event.
To better understand the impact's effects and timing, a team of researchers, including Marc Biren from Arizona State University's School of Earth and Space Exploration, analyzed drilling samples from the Ocean Drilling Project site 1073. Their work aimed to refine the dating of the ejecta materials using advanced techniques.
The team, which also included Jo-Anne Wartho, Matthijs Van Soest, and Kip Hodges, applied the uranium-thorium-helium dating technique to the samples. This method allowed them to establish a more precise timeline for when the materials were ejected and how they cooled and settled.
Their findings were recently published in Meteoritics & Planetary Science.
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“Determining accurate and precise ages of impact events is vital in our understanding of Earth's history,” Biren said. “In recent years, for example, the scientific community has realized the importance of impact events on Earth’s geological and biological history, including the 65-million-year-old dinosaur mass extinction event linked to the large Chicxulub impact crater.”
The team focused on zircon crystals, which preserve evidence of shock metamorphism caused by the high pressures and temperatures of impact events. These crystals, about the thickness of a human hair, were central to their investigation.
“Key to our investigation were zircon — or more precisely: zirconium silicate — crystals found in oceanic sediments of a borehole almost 400 kilometers (250 miles) northeast of the impact site in the Atlantic Ocean,” said co-author Wartho, who started the study as a lab manager at the Mass Spectrometry Lab at ASU.
For this study, Biren collaborated with Wartho (now at GEOMAR Helmholtz Centre for Ocean Research Kiel), Van Soest, and Hodges to prepare samples for analysis and date zircon crystals using the uranium-thorium-helium method. Biren identified and processed shocked zircon fragments for imaging and chemical analysis with an electron microprobe.
“This research adds a tool for investigators dating terrestrial impact structures,” Biren said. “Our results demonstrate the uranium-thorium-helium dating method’s viability for use in similar cases, where shocked materials were ejected away from the crater and then allowed to cool quickly, especially in cases where the sample size is small.”
The study not only contributes to the understanding of the Chesapeake Bay impact event but also highlights the broader significance of impact events on Earth’s geological and biological history.
The ability to accurately date such events enhances our comprehension of their effects on the planet’s development and the history of life.
Five Largest Craters on Earth
The five largest impact craters on Earth by diameter are:
Vredefort Crater (South Africa) – ~250–300 km
- Age: ~2.02 billion years
- The largest and oldest confirmed impact structure on Earth, located in South Africa. The original crater has been eroded over time, but the remaining structure provides valuable insights into ancient impact events.
Chicxulub Crater (Mexico) – ~180 km
- Age: ~66 million years
- This crater, located beneath the Yucatán Peninsula, is linked to the mass extinction event that wiped out the dinosaurs. It is one of the best-preserved large impact craters on Earth.
Sudbury Basin (Canada) – ~130 km
- Age: ~1.85 billion years
- Located in Ontario, Canada, the Sudbury Basin is one of the oldest impact structures on Earth. It has been heavily modified by erosion and subsequent geological processes.
Popigai Crater (Russia) – ~90 km
- Age: ~35.7 million years
- Situated in Siberia, the Popigai Crater is one of the largest impact structures in Russia. The impact event is believed to have contributed to a minor extinction event.
Manicouagan Crater (Canada) – ~85 km
- Age: ~214 million years
- Located in Quebec, Canada, this well-preserved crater is known for its distinct ring-shaped lake. It is one of the best-studied impact structures on Earth.
These impact craters provide critical evidence of past asteroid or comet collisions and their effects on Earth's geological and biological history.
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