GEOLOGY 103 Lecture 5: Lecture5 Geological Processes Cratering
Document Summary
Impact craters: the most common landform in the solar system, great variety in size and type, dominate old planetary surfaces, impacts can have catastrophic effect on planetary atmospheres, profound in uence on history of life on earth. What has been observed on earth: an object exploded in the atmosphere over tunguska, siberia, in 1908 and devastated a large area of countryside. Where e= kinetic energy m= mass v= velocity r= radius. Tsar bomba 1961 was approximately 20 megatons. It has been estimated that objects around 38. 5 megatons strike earth once per century to once per millennium. Impact cratering: a crater-forming impact has never been observed, effect is the same as a point-source explosion, nuclear and large conventional explosions can be used as models. Formation of craters: compression stage, impact, beginning of shock wave, compression wave spreads, excavation stage, compressed rock rebounds (rarefaction wave, ejecta fallback (fracture system forms)
