PREDICTIVE ELEMENTS OF LARGE BODY IMPACTS IN GEOLOGIC HISTORY

Large-body impacts cannot be predicted, although the probability (size -frequency) of large impacts on the Earth has been worked out, yieldin g frequencies of the order of one impact of a l-km body every 500 000 years. Another type of prediction, however, is that forthcoming from t he consequences of a large-body impact. Prediction as validation of th eory. What can be predicted are the consequences of a large impact, ra nging from local and regional ejecta blankets to global climate change s leading to mass extinctions. It is the fulfillment of such predictio ns that has rendered strength to the impact-extinction theory for the Cretaceous-Tertiary (K/T) boundary, in contrast to predictions attache d to widespread volcanism, such as at the Deccan traps in India, or se a-level changes.