Cretaceous Ground Zero

Read the article "Cretaceous Ground Zero" from the June 1991 issue of Natural History and answer these questions in complete sentences:

  1. Why did Berkeley scientists first measure the iridium in the pencil-thick sheet of gray clay found in Gubbio Italy ?
  2. How many times the expected level of iridium did they find?
  3. Where did they decide the extra iridium came from?
  4. What were two other pieces of evidence found to support the meteorite impact theory?
  5. What is the "ejecta layer"?
  6. Describe the ejecta layer in Haiti?
  7. Why was the thickness of the ejecta layer in Haiti important?
  8. What did scientists use to determine that the meteor had struck on the edge of an ocean basin?
  9. How did the K-T boundary deposits in Cuba support the ocean impact hypothesis?
  10. How did ocean-bottom sediment disturbance help narrow the search for the impact site?
  11. What did the researchers look for when they found a circular geologic feature?
  12. The meteor impact would have produced immediate lethal effects, but what other effect would have made the Chicxulub impact even more destructive?
  13. Which crater is the impact crater?