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This list includes all 60 confirmed impact structures in North America in the Earth Impact Database (EID). These features were caused by the collision of large meteorites or comets with the Earth. For eroded or buried craters, the stated diameter typically refers to an estimate of original rim diameter, and may not correspond to present surface ...
Less than ten thousand years old, and with a diameter of 100 m (330 ft) or more. The EID lists fewer than ten such craters, and the largest in the last 100,000 years (100 ka) is the 4.5 km (2.8 mi) Rio Cuarto crater in Argentina. [2]
Impact craters produce melted rocks as well, but usually in smaller volumes with different characteristics. [6] The distinctive mark of an impact crater is the presence of rock that has undergone shock-metamorphic effects, such as shatter cones, melted rocks, and crystal deformations. The problem is that these materials tend to be deeply buried ...
The magnetic anomalies Bangui and Jackpine Creek, [145] the gravity anomalies Wilkes Land crater and Falkland Islands, [350] and others have been considered as being of impact origin. Bangui apparently has been discredited, [ 25 ] [ 351 ] but appears again in a 2014 table of unconfirmed structures in Africa by Reimold and Koeberl.
Impact melt rocks are thought to fill the central part of the crater, with a maximum thickness of 3 kilometers (1.9 mi). The samples of melt rock that have been studied have overall compositions similar to that of the basement rocks, with some indications of mixing with carbonate source, presumed to be derived from the Cretaceous carbonates.
The meteorite that caused the impact crater is estimated to have been 170 m (560 ft) in diameter with a mass of 9 × 10 9 kg (2.0 × 10 10 lb) and impact velocity of 30 km/s (67,000 mph). The crater is 6 km (3.7 mi) in diameter, and fossils found in the rock filling the crater suggest it dates to the Middle Ordovician Period, about 455 to 430 ...
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