The Chesapeake Bay Impact Crater was formed by the impact of an extraterrestrial bolide that hit about 35.5 million years ago, in the late Eocene Epoch. It is one of the best-preserved 'wet-target' or marine impact craters, and the largest impact crater in the USA. Continued slumping of sediments over the rubble of the crater have helped shape Chesapeake Bay. Image File history File links The Chesapeake Bay impact crater, created 35 million years ago. ... Artists impression of a major impact event. ... Extraterrestrial, as an adjective, refers to something that originates, occurs, or is located outside Earth or its atmosphere. ... The term bolide (from the Greek βολις, bolis, missile) can refer to either an extraterrestrial body that collides with the Earth, or to an exceptionally bright, fireball-like meteor regardless of whether it ultimately impacts the surface. ... The Eocene epoch (56-34 MYA) is a major division of the geologic timescale and the second epoch of the Palaeogene period in the Cenozoic era. ... The word epoch can mean either an interval of time, or a particular point in time used as a reference point. ... Ocean (from Okeanos, a Greek god of sea and water; Greek ωκεανός) covers almost three quarters (71%) of the surface of the Earth. ... This article is about impact craters, also known as meteor craters. ... Sediment is any particulate matter that can be transported by fluid flow and which eventually is deposited as a layer of solid particles on the bed or bottom of a body of water or other liquid. ... Chesapeake Bay - Landsat photo The Chesapeake Bay is the largest estuary in the United States. ...

During the warm late Eocene, sea levels were high, and the Tidewater region of Virginia lay in the coastal shallows. The shore of eastern North America, about where Richmond, Virginia is today, was covered with dense tropical rainforest, and the waters of the gently sloping continental shelf were rich with marine life that was depositing dense layers of lime from their microscopic shells. The Eocene epoch (56-34 MYA) is a major division of the geologic timescale and the second epoch of the Palaeogene period in the Cenozoic era. ... For considerations of sea level change, in particular rise associated with possible global warming, see sea level rise. ... The Tidewater region of Virginia is the southeastern portion of the Commonwealth of Virginia, centered on Hampton Roads. ... A coastal image featured on a United States postal stamp. ... World map showing location of North America A satellite composite image of North America North America is a continent in the northern hemisphere, bounded on the north by the Arctic Ocean, on the east by the North Atlantic Ocean, on the south by the Caribbean Sea, and on the west... Downtown Richmond as seen from the James River Motto: Sic Itur Ad Astra (Such is the way to the Stars) Nickname: River City Location in Virginia Founded  -Incorporated  1607   County  Independent city Mayor  Douglas Wilder Area  - Total  - Water  162. ... Tropical and subtropical moist broadleaf forests, also known as tropical rain forests, are a tropical and subtropical biome. ... The continental shelf is the extended perimeter of each continent, which is covered during interglacial periods such as the one we live in by relatively shallow seas and gulfs. ... Calcium carbonate is a chemical compound, with chemical formula CaCO3. ... The hard, rigid outer calcium cumbonate covering of certain animals is called a shell. ...

The bolide impacted at a speed of many kilometers per second, punching a deep hole through the sediments and into the granite continental basement rock. The bolide itself was completely vaporised, with the basement rock being fractured to depths of 8 kilometers, and a 'peak ring' being raised around it. The deep crater, 38 km across, is surrounded by a flat-floored terrace-like ring trough with an outer edge of collapsed blocks forming ring faults. The entire circular crater is about 85 km in diameter and 1.3 km deep, an area twice the size of Rhode Island, and nearly as deep as the Grand Canyon. Granite is a common and widely-occurring group of intrusive felsic igneous rocks that form at great depths and pressures under continents. ... Basement rock usually refers to the thick foundation of ancient, and oldest metamorphic and igneous rock that forms the crust of continents, often granite. ... A kilometre (American spelling: kilometer) (symbol: km) is a unit of length equal to 1000 metres (from the Greek words khilia = thousand and metro = count/measure). ... State nickname: The Ocean State, Little Rhody Other U.S. States Capital Providence Largest city Providence Governor Donald Carcieri Official languages None Area 4,005 km² (50th)  - Land 2,709 km²  - Water 1,296 km² (32. ... Grand Cañon at the foot of the Toroweap - looking east, by William Henry Holmes The Grand Canyon is a colorful, steep-sided gorge, carved by the Colorado River, in northern Arizona. ...

The surrounding region suffered massive devastation. USGS scientist David Powars, one of the impact crater's discoverers, has described the immediate aftermath: "Within minutes, millions of tons of water, sediment, and shattered rock were cast high into the atmosphere for hundreds of miles along the East Coast." An enormous seismic tsunami engulfed the land and possibly even overtopped the Blue Ridge Mountains. The sedimentary walls of the crater progressively slumped in, widened the crater, and formed a layer of huge blocks on the floor of the ring-like trough. The slump blocks were then covered with the rubble or 'breccia'. The entire bolide event, from initial impact to the termination of breccia deposition lasted only a few hours or days. In the perspective of geological time, the 1.2 km-thick breccia is an instantaneous deposit. The crater was then buried by additional sedimentary beds, which have accumulated during the ensuing 35 million years. The United States Geological Survey (USGS) is a scientific agency of the United States government. ... Earths atmosphere is the layer of gases surrounding the planet Earth and retained by the Earths gravity. ... A mile is any of several units of distance, or, in physics terminology, of length. ... The tsunami that struck Malé in the Maldives on December 26, 2004. ... Blue Ridge Mountains (NPS) Most of the rocks that form the Blue Ridge Mountains, United States, are ancient granitic and metamorphosed volcanic formations, some exceeding one billion years in age. ... Breccia, derived from the Latin word for broken, is a sedimentary rock composed of angular fragments in a matrix that may be of a similar or a different material. ...

Until 1983, no one suspected the existence of such a crater buried 300–500 meters beneath the lower part of Chesapeake Bay and its surrounding peninsulas. The first hint was a 20 centimeter-thick layer of ejecta that turned up in a drilling core taken off Atlantic City, New Jersey, far to the north. The layer contained the fused glass beads called tektites and shocked quartz grains that are unmistakable signs of a bolide impact although some researchers suggest that tektites are more likely volcanic ejecta from the Moon. 1983 is a common year starting on Saturday of the Gregorian calendar. ... Chesapeake Bay - Landsat photo The Chesapeake Bay is the largest estuary in the United States. ... A peninsula is a geographical formation consisting of an extension of land from a larger body, surrounded by water on three sides. ... Atlantic City is a city located in Atlantic County, New Jersey, USA. As of the 2000 census, the city had a total population of 40,517. ... The materials definition of a glass is a uniform amorphous solid material, usually produced when a suitably viscous molten material cools very rapidly, thereby not giving enough time for a regular crystal lattice to form. ... A tektite Tektites (from Greek tektos, molten) are natural glass objects, up to a few centimeters in size, which are believed to have been formed by the impact of large meteorites on Earths surface, although some researchers favor an origin from the Moon as volcanic ejecta. ... Shocked quartz is a form of quartz that has a microscopic structure that is different from normal quartz. ...

A part of one of the rock samples collected on Apollo 12, lunar sample 12013, has a composition which is remarkably similar to some tektites. It is especially similar to high-magnesium javenites (part of the Australasian field). Sample 12013 is inhomogenous in that it is composed of two types of materials, light and dark. The light, acidic portion is composed of up to 71 percent silicon dioxide. The dark portion resembles KREEP rocks. The abundances of 20 of 23 elements tested from the acidic portion of the sample showed a striking similarity to high-magnesium tektites. The major elements matched well, the minor and trace elements did not.

In 1993 oil exploration revealed the extent of the crater. 1993 is a common year starting on Friday of the Gregorian calendar and marked the Beginning of the International Decade to Combat Racism and Racial Discrimination (1993-2003). ... Petroleum geology is a term used to refer to the specific set of geological disciplines that are applied to the search for hydrocarbons (oil exploration). ...

The continual slumping of the rubble within the crater has affected the flow of the rivers and shaped Chesapeake Bay. The impact crater created a long-lasting topographic depression, which helped predetermine the course of local rivers and the eventual location of Chesapeake Bay. Most important for present-day inhabitants of the area, the impact disrupted aquifers. The present freshwater aquifers lie above a deep salty brine, making the entire lower Chesapeake Bay area susceptible to groundwater contamination. A submarine slope movement which may be a result of tidal forces acting on an unstable slope, or from a large seismic event near the affected body of water. ... For the Second World War frigate class, see River class frigate The Murray River in Australia A river is a large natural waterway. ... Surface of the Earth Topography, a term in geography, has come to refer to the lay of the land, or the physiogeographic characteristics of land in terms of elevation, slope, and orientation. ... An aquifer is an underground layer of water-bearing permeable rock, or permeable mixtures of unconsolidated materials (gravel, sand, silt, or clay) (see also groundwater). ... Brine is water saturated or nearly saturated with salt. ... Groundwater is water flowing within aquifers below the water table. ...

External links

• A brief introduction to the Chesapeake Bay Impact Crater.
• USGS, 'Investigating the Chesapeake Bay Impact Crater.'
• USGS, 'The Chesapeake meteorite: message from the past.'
• 'The Chesapeake Bay bolide: modern consequences of an ancient cataclysm.'
• Earth Impact Database, a website concerned with over 160 identified impact craters on the Earth.
• Satellite image of the region (from Google Maps)