Nadir crater
Nadir crater is a buried impact crater on the Guinea Plateau in the Atlantic Ocean, 248 mi (400 km) off the coast of Guinea. The feature is named after the Nadir Seamount, located 100 km to the south. The paper announcing the discovery of the feature was published in Science Advances in 2022,[1] with an impact origin being confirmed in 2024. The crater is around 9.2 kilometres (5.7 mi) in diameter, and formed around 66 million years ago, close to the K-Pg boundary when a small asteroid struck the ocean floor.[2]
Impact event
[edit]The crater features all characteristics of an impact event: appropriate ratio of width to depth, the height of the rims, and the height of the central uplift.[3] It was formed at or near the Cretaceous–Paleogene boundary about 66 million years ago, around the same time as the Chicxulub crater.[1] Numerical simulations of crater formation suggested a sea impact at the depth of around 800 m of a ≥400-m asteroid.[1] It would have produced a fireball with a radius of >5 km,[1] instant vaporization of water and sediment near the seabed,[1] tsunami waves up to 1 kilometer high around the crater[3] and substantial amounts of greenhouse gases released from shallow buried black shale deposits.[1] A magnitude 6.5–7 earthquake would have also been produced.[4] The estimated energy yield would have been around 2×1019 Joules (around 5000 megatons).[1]
In 2024, detailed seismic data analysis confirmed the impact nature of the structure beyond reasonable doubt.[2]
To obtain a more precise and narrowly constrained age of the crater, which currently has an uncertainty about one million years, drilling sediment cores from the crater and testing of minerals from the crater floor is key and has been proposed.[4][5]
Impactor
[edit]The impactor is estimated to be around 400 m in diameter, roughly equivalent to the size of the Bennu asteroid.[1] The authors of the paper speculated that it may have been part of a binary asteroid with the Chicxulub impactor or part of an impact cluster, but it is also probable that it is unrelated.[1] Impacts similar in size to Nadir occur on average every 50,000 to 100,000 years.[6]
References
[edit]- ^ a b c d e f g h i Nicholson, Uisdean; Bray, Veronica J.; Gulick, Sean P. S.; Aduomahor, Benedict (17 August 2022). "The Nadir Crater offshore West Africa: A candidate Cretaceous-Paleogene impact structure". Science Advances. 8 (33): eabn3096. Bibcode:2022SciA....8N3096N. doi:10.1126/sciadv.abn3096. PMC 9385158. PMID 35977017. S2CID 251646087.
- ^ a b Nicholson, Uisdean; Powell, William; Gulick, Sean; Kenkmann, Thomas; Bray, Veronica J.; Duarte, Debora; Collins, Gareth S. (2024-10-03). "3D anatomy of the Cretaceous–Paleogene age Nadir Crater". Communications Earth & Environment. 5 (1). doi:10.1038/s43247-024-01700-4. ISSN 2662-4435.
- ^ a b Katie Hunt (18 August 2022). "Scientists discover a 5-mile wide undersea crater created as the dinosaurs disappeared". CNN. Archived from the original on 18 August 2022. Retrieved 18 August 2022.
- ^ a b Kornei, Katherine (19 September 2022). "Impact Crater off the African Coast May Be Linked to Chicxulub: The underwater crater, spotted serendipitously in commercial observations of seafloor sediments, is believed to have formed at roughly the same time as the famous Cretaceous-Paleogene impact event". eos.org. Retrieved 22 September 2022.
- ^ Uisdean Nicholson; Sean Gulick; Veronica Bray; Tom Dunkley-Jones; Christian Maerz; Thomas Wagner; Pim Kaskes; Elisabetta Erba; Cherif Diallo; Thomas Davison; Chris Lowery; Cornelia Rasmussen; Daniel Condon (2021). "Into the Nadir: a new Cretaceous-Paleogene impact structure?". IODP. Archived from the original on 25 September 2021. Retrieved 18 August 2022.
- ^ Andrews, Robin George (2022-08-17). "African Crater Adds an Asteroid Strike to the Late Dinosaur Era". The New York Times. ISSN 0362-4331. Retrieved 2022-08-23.