Arandas (crater) km in diameter) they usually have a central peak. The peak is caused by a rebound of the crater floor following the impact. Sometimes craters expose layers that were buried. Rocks from deep underground are tossed onto the surface. Hence, craters can show us what lies deep under the surface. Arandas (crater) Arandas Crater is a crater in the Mare Acidalium quadrangle of Mars, located 42.77° North and 15.17° West. It is 24.76 km in diameter and is named after the town of Arandas in Mexico. South is the scalloped terrain of Cydonia Labyrinthus and further south is Cydonia Colles,
Chicxulub crater Bakker, argue that such an impact would have killed frogs as well as dinosaurs, yet the frogs survived the extinction event. Gerta Keller of Princeton University argues that recent core samples from Chicxulub prove the impact occurred about 300,000 years "before" the mass extinction, and thus could not have been the causal factor. However, this conclusion is unsupported by radioactive dating and sedimentology. The main evidence of such an impact, besides the crater itself, is contained in a thin layer of clay present in the K–Pg boundary across the world. In the late 1970s, the Alvarezes and colleagues reported that