The crater off West Africa is believed to be caused by a large asteroid; the crater is ".. a near-circular crater rim of 9.2 km and an outer brim of ~23 km diameter ...".
The big deal, IMHO:
The Nadir Crater is a proposed hypervelocity impact structure of approximately Cretaceous–Paleogene (K-Pg) boundary age (66 Ma). The similarity in age of the crater with the 200 km Chicxulub crater in Mexico, has led to the suggestion that the end-Cretaceous extinction event may have been associated with more than one impact—either break-up of a parent asteroid in near-Earth orbit or as part of a longer-lived (~1–2 My) temporal cluster of impacts.
The big deal, IMHO:
The Nadir Crater is a proposed hypervelocity impact structure of approximately Cretaceous–Paleogene (K-Pg) boundary age (66 Ma). The similarity in age of the crater with the 200 km Chicxulub crater in Mexico, has led to the suggestion that the end-Cretaceous extinction event may have been associated with more than one impact—either break-up of a parent asteroid in near-Earth orbit or as part of a longer-lived (~1–2 My) temporal cluster of impacts.