Comparisons with Other Impact Craters

Abstract

The Chesapeake Bay crater is large and well preserved, and exhibits more impactgenerated features (including secondary craters) than most other terrestrial impact structures yet studied, but it appears not to have caused an immediately subsequent mass extinction. These properties make it an important benchmark for improving our understanding of the dynamics of crater formation, ejecta generation and distribution, breccia origin and deposition, and consequent environmental perturbations, or lack thereof. A few known craters in its size class (75–100 km diameter), and several smaller ones, exhibit some or most features of the Chesapeake Bay crater (Table 10.1), but in several key aspects, the Chesapeake Bay crater does not conform to general conceptual models widely applied to explain the formation of complex terrestrial and planetary craters. Some of its unusual features (perhaps all) appear to be related to its original submarine location, which presented a three-layered target composed of: (1) a moderately deep (∼300 m) water column; (2) a water-saturated, unconsolidated sediment column (300–500 m thick); and (3) a basement of consolidated crystalline (granitoid and metasedimentary) rocks. Other considerations, such as impactor size, composition, and trajectory, however, also may be pertinent to explaining some of the differences. In order to identify the principal differences, we compare the attributes of the Chesapeake Bay crater with those of other known subaerial and submarine craters on Earth, as well as with some of those on other planetary bodies.