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Video Study Guide

THE DINOSAURS: The Death of the Dinosaur

This video presents several lines of evidence supporting the idea that the mass extinction at the end of the Cretaceous, the mass extinction that included the extinction of dinosaurs, was caused by an asteroid or comet impact. Some of this same evidence is also presented in your textbook (Chapter 16).

The video is basically divided into eleven parts. Part 1 is an introduction to mass extinctions, including when Cuvier established the concept of extinction and some possible causes. In part 2, Walter Alvarez describes how a clay layer at the Cretaceous-Tertiary boundary in Italy led to the idea that the mass extinction at the end of the Cretaceous resulted from an asteroid impact. In part 3, David Fastovsky and colleagues conduct a dinosaur census in latest Cretaceous strata in Montana and demonstrate that the dinosaurs went extinct abruptly. Part 4 turns the spotlight on comet hunters, Gene and Caroline Shoemaker. In part 5, paleontologist Peter Ward discusses his work in Spain showing that shelled marine squid-like animals called ammonites also went extinct abruptly. In part 6, Jay Melosh describes what would happen if an asteroid 6 km in diameter struck the earth. In part 7, additional evidence for an asteroid impact is discussed. Part 8 describes how the impact crater was found to lie in the subsurface of the Yucatan Peninsula of Mexico. In part 9, Alan Hildebrand describes seafloor sediments deposited from the giant tsunami generated by the impact. All of the evidence presented to this point indicates that went extinct as a result of an asteroid impact. In part 10, Bob Bakker offers up another explanation.

Questions: Fill in the following blanks based on the video.

Part 1. Extinctions

1. Over ______________ years ago, George Cuvier established the concept of extinction.

2. The fossil record shows individual species of sea and land creatures disappearing at intervals of 5 million years or so. But from time to time there appears to have been more dramatic

__________________________ extinctions, when virtually all plant and animal groups lost at least some of their numbers. One at the end of the Triassic Period; another at the end of the Jurassic. Each of which opened the door to a new family of dinosaurs. And then at the end of the Cretaceous Period, there came one final extinction, that ended the reign of the dinosaurs for all time..

3. Who is exterminating the great species again and again and again? … One good suspect is

the _____________________________ - a change in the climate of the planet. Throughout the age of the dinosaurs, the average temperature on the earth was warmer than it is today. … Or perhaps an explosion of volcanic activity that spewed red hot volcanic dust into the atmosphere, blotting out the sun’s rays.

Part 2. Asteroids

4. Or maybe the newest and sexiest theory has the answer. Maybe something out there from the cosmos smacked into the earth sending up a plume of dust, blotting out the sun’s heat and freezing the dinosaurs to death. Something huge, something full of energy. An

____________________.

5. Walter Alvarez notes that they kept walking past this very intriguing layer of _____________, that lay between the Cretaceous and Tertiary, a layer that was red and green clay.

6. As part of the work that Luis Alvarez did, the clay was found to contain huge amounts of

cosmic dust, specifically a platinum-like metal called ______________________. Alvarez knew that while Iridium is rare on the surface of the earth, it is abundant in asteroids and comets.

7. Alvarez notes that what they finally came up with was the idea that dust and droplets of impact melt that had been thrown out of the atmosphere and dispersed all over the planet would make it so dark that photo synthesis would stop and the food chains would collapse and the extinctions would be the result of starvation when the food supplies ran out. …. And that there was a little more to evolution than Darwin realized. … Darwin said that in order for a species to survive and flourish and produce descendents, it had to be well adapted. … But

in addition, there’s an occasional really __________ day when a huge rock falls out of the sky and makes terrible environmental disturbances.

Part 3. Dinosaur Census

8. In Makoshika State Park in southern Montana, Fastovsky and Gabrielle found that the

predominant animal that [they] found in [their] survey was __________________________. Ceratopsians are really abundant at the end of the Cretaceous. And the next one would be the duck-billed dinosaurs, probably Edmontosaurus. And [they] found a lot of ornithomimids and animals like that. But [they] also found lots of the small carnivores, the ones that scavenge and pick up after the other ones have killed them. And [they] do have Tyrannosaurus rex too. There doesn’t seem to be any evidence for a gradual decline in the diversity of the dinosaurs. In fact, the study shows that in geological terms, their extinction was instantaneous.

Part 4. Comet Hunters

9. When the Shoemakers began their program in 1973, there were a dozen known earth crossing asteroids, all found accidentally over the course of some decades. At the time of the video,

after their systematic search, they had raised that number to over a _______________.

10. The Shoemakers estimate that there are about 1500 asteroids larger than __________ km whose orbits cross that of the earth.

Part 5. Ammonites

11. During the Mesozoic these creatures were fantastically abundant. There were _____ thousand species of them. … They occupied the place of fish today. They were really the fish of the Cretaceous oceans. … And it seems that the ammonites at the end of the Cretaceous were thriving, they were producing new species, they were flourishing in their communities, and then suddenly without warning they disappeared.

Part 6. Asteroid Impact

12. This enormous volume of rock will be rushing toward the earth at 50,000 mph. … When the asteroid strikes the ground, it buries itself in the earth in a period of only 1 second. It opens a crater, a hemispherical hole in the ground that reaches a diameter of 30 miles about 10 seconds after the impact occurs. At that time it is 15 miles deep, it's lined with red hot rock debris streaming outward forming a plume heading into the sky. At that time the crater floor begins to rise back up at the same time the diameter of the crater continues to increase. It goes on until it reaches a diameter of about 100 miles before it stops growing. What happens next is really interesting. As the asteroid plunges into the ground, it creates pressures about equal to that of the earth's core. Under those pressures the asteroid and also some of the earth rock melt and vaporize and expand back out of the crater as a plume or glowing cloud of very high velocity gas and dust. This cloud expands at velocities up to the earth's escape velocity sending the debris into ballistic orbits that eventually rain back all over the earth. Trillions of tiny particles of this kind would fill the sky, radiating heat toward the ground. … Even green vegetation would dry out and begin to burst into flames spontaneously as a result of this

thermal radiation, causing global forest ____________________.

Part 7. Carbon spheres, Iridium and Shocked Quartz

13. Millions of microscopic ______________ spheres have been found in the clay that was deposited at the end of the Cretaceous period - soot from some enormous conflagration.

14. Izett finds that the clay also contains unusual and he claims significant grains of __________. Viewed in polarized light quartz usually appears featureless. … quartz from the clay contains these very peculiar lines through the quartz grain. They're oriented in this particular grain in this direction and this direction. These are called shock lamellae, and the only place these have been found in rocks of the earth's crust happen to be at high yield nuclear explosion sites or at know meteor impact sites.

Part 8. Chicxulub Crater

15. Geophysicist Glen Penfield began noticing a pattern of extraordinary symmetry in the

__________________ anomalies. … An enormous ring of very intense magnetic anomalies that you can see here on the map, about 70 km across. Very, very strong gradients in the field. Further out, a ring of very subtle features with a diameter of about 210 km. A similar sort of configuration of anomalies is visible in the gravitational data. … A central ring of high gravity anomalies indicating more dense material here in the center, again about 65 km across. Then a gravity low, indicating lower density material and finally another gravity high 180 km in diameter. … The most likely explanation … was that of a gigantic meteor impact.

16. Penfield found that in rocks from a well drilled to 1500 meters, that for the ______________ thousand meters it was a monotonous sequence of white limestone rock. And then the well site geologist reported a broken up kind of greenish material for a substantial thickness and then finally something that looked like glass.

Part 9. Tsunami Deposits & Chicxulub 2

17. Hildebrand found that unlike most places where the Cretaceous and Tertiary rocks are separated by a narrow clay layer, one that is no more than a half inch thick, on the bank of

the Brazos River in Texas there is a rubble filled interval that is almost ______ feet thick. Here the dividing line between the world of dinosaurs and the world that came after is startling clear.

18. In particular this lump of gray _______________, which is a bit indistinct. You can see it goes around like so. This is a boulder about 3 feet across. Something happened that was able to uproot this gray clay from the Cretaceous seafloor and transport and dump it here. Similar deposits of rubble occur all along the southern coast of North America at the K-T boundary.

19. Florentine Maurasse describes a 2 cm thick layer of sediment at the base of the Belloc

Formation in Haiti at the K-T boundary that contains tektites, droplets of ________________ material splashed out of the earth by an impact and then frozen into form.

20. We found shocked _____________________ in samples from the Chicxulub well that had been stored in New Orleans.

Part 10. Disease

21. Bob Bakker thinks that when dinosaurs crossed the land bridges they were exposed to new

strains of _____________________ that could have wreaked havoc among dinosaur populations. … When dinosaurs spread, they spread disease and became in turn the victims of their own relentless exploration.

Answers:

1. 200

2. mass

3. environment

4. asteroid

5. clay

6. Iridium

7. bad

8. Triceratops

9. hundred

10. one

11. 12

12. fires

13. carbon

14. quartz

15. magnetic

16. first

17. 3

18. clay

19. molten

20. quartz

21. disease