Death from Outer Space, Did an Asteroid Impact Wipe out
the Dinosaurs?
The asteroid Gaspra - 7x7x12 miles
A Gallery of Asteroids
Was it really an asteroid? We must
have multiple working
hypotheses!
Dinosaurs forgot to board the Ark
K/T Boundary 66 MYAge of Dinosaurs
Geologic Time Scale
K-T extinction record
Wyoming
The K/T impact clay layer, Gubbio, Italy. Iridium anomaly first found here.
K = Cretaceous
T = Tertiary
K
T
Iridium anomaly in the K/T rocks at Gubbio, Italy, in parts per billion (PPB).
K/T boundary
20 cm
10 cm
0 10
PPB
0
The K/T boundary in New Mexico is marked by the white claystone just above the head of the hammer.Claire Belcher, Geology Department, University of London
The white claystone layer marks the K/T boundary
The K/T boundary in Spain
Known distribution of sites with K/T Iridium anomaly
Map of major impact sites in North America
The Berringer Crater in Arizona, 50,000 years old. 4000 ft across -- formed by 100 ft meteorite.
Why craters are so much larger than the objects that make them. Like shooting a bullet into a soft target.
The Manicougan Crater in Quebec,late Triassic in age -- 100 km diameter
Gosses Bluff, Australia. Crater age is 142 Ma, but no mass extinction.
A 4 km wide asteroid hit
America at the end of the Eocene,
35 m.y. ago
the Chicxulub Crater
Late Cretaceous Paleogeography
Gravity anomaly map of Yucatan area
3D representation of gravity anomaly
Another representation of the gravity anomaly on the Yucatan Penninsula: the Chicxulub Crater
Tektites from the asteroid impact –melted rock
Enlargement of a tektite from the Atlantic sea floor
Tektites from the K/T boundary in New Jersey
Map showing distribution of tektites by size. Tektites are largest near Yucatan.
Shocked quartz from the asteroid impact
The impact: 66 MY ago
The 6-mile diameter asteroid heading towards Earth, 66 MY ago
The start of a bad day, 66 MY ago
Velocity = 20 km/s or 40,000 mph
Kinetic energy about to be converted to thermal energy
Impact on the Yucatan Peninsula!
The power of millions of atomic bombs
The K/T impact released more energy than the World’s Nuclear Arsenal
Primary Killing Mechanisms: Two Hypotheses
• Infrared thermal pulse “broiled” exposed animals for several hours after the impact.
• A massive dust cloud blanketed the Earth, blocking sunlight. This caused a collapse of the food chain and severe global cooling.
Broiled Dinosaurs
Thermal radiation 7X greater than the sun
Fiery debris falls back to Earth over large areas starting forest fires
Worldwide forest fires consumed about 30% of all terrestrial biomass.
Blast wave and dust cloud from the impact
Dust from the impact, and smoke from fires, blanketed the Earth and blocked the sunlight.
Temperature anomaly map 15 days after impact
Temperature Change
The Yucatan, a few days after impact
The crater about 1000 years after impact
Looking for evidence of the Yucatan impact outside the Caribbean. The Ocean Drilling Project recovers cores off the east coast of Florida in 1997.
The drilling ship can send a drill string to the ocean floor and recover core.
Cores layed out on the ship
Section of core with K/T boundary interval.
geoweb.princeton.edu/.../massex.html
Forams from the Cretaceous
Forams from the Tertiary
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