A highly unusual category of general coastal morphology is created by asteroid impacts at some time in the geologic past. Asteroid impact creates a circular or ovoid crater beneath which is a brecciated zone that extends many thousand meters below the former surface of the Earth’s crust. The eroded relics of these ancient craters have been called “astrob-lemes” (Dietz 1961).
Three coastal areas in North America are believed to owe their morphology, at least in part, to asteroid impact. They are:
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Chesapeake Bay , and adjacent areas of Maryland and Virginia. The coast is characterized by an unusual pattern of a drowned dendritic drainage system, that is to say, organized like the branches of a well-shaped tree. It is fed by the valleys of the Susquehanna, Potomac, and Rappahanock rivers. The asteroid or “bolide” struck 35.2 (+/−0.3) million years ago, in Late Eocene times in soft coastal plain and shelf sediments which to the impacting object, about 3–5 km in diameter and...
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Bibliography
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Marvin UB (1990) Impact and its revolutionary implications for geology. Geol Soc Am Spec Pap 247:147–154
Poag CW (1997) The Chesapeake Bay bolide impact: a convulsive event in Atlantic coast plain evolution. Sediment Geol 108:45–90
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Fairbridge, R.W. (2018). Asteroid-Impact Coasts. In: Finkl, C., Makowski, C. (eds) Encyclopedia of Coastal Science . Encyclopedia of Earth Sciences Series. Springer, Cham. https://doi.org/10.1007/978-3-319-48657-4_19-2
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