2. FINDING THE CRATER

3. Asteroid impact—different types of evidence
10 km wide asteroid
Massive crater
Where is it?

4. Evidence in 65 MYO rocks
Rock boundary between Cretaceous and Tertirary periods (K-T boundary)
Time of asteroid impact

5. K-T boundary is rich in iridium
Iridium is rare in the Earth’s crust, however, abundant in comets and asteroids
K-T asteroid was vaporized on impact
Fine particles of iridium traveled high into the atmosphere
Distributed all over the Earth

6. Deposits of the K-T boundary hold clues…
Deposits worldwide contain pieces of melted or crushed rocks blasted from impact site
ejecta

7. Ejecta – spherules and tektites
On impact, asteroid left some of surrounding rock in Earth’s crust melted is it was ejected from impact site
Melted rock particles particles fell back on planet and cooled, formed into glass-like objects (sperules and tektites)

8. Spherules in K-T sites worldwide
Spherules—glassy spheres (0.1 mm—2 mm)
Found close and far from impact site

9. Tektites Tektites—closer to impact site Nickel-rich spinels
2-3 cm in size
More irregular shapes
Nickel-rich spinels
Fusion/oxidation of asteroid impact
Found in K-T sites throughout world

10. Shocked quartz High pressure of asteroid impact
Quartz grains to shatter/fracture