When I go hiking in the woods I like to see animals: deer, rocky mountain sheep, squirrels, and hawks to name a few. What I dont see, but what I wish I could see, are dinosaurs. Anyone who is involved in geology is attracted to dinosaurs on some level, as are most people in the world. We would all like to be able to see dinosaurs when we hike in the woods. Who wouldnt? But why are there no more dinosaurs, why have we been deprived of the sight of Triceratops grazing on the plains or a duck-billed dinosaur rising gargantuan-like in front of us? We cannot see dinosaurs any more because they went extinct, disappeared, were wiped out 65 million years ago. They had lived on this planet for 160 million years, yet something killed them off 65 million years ago creating the grandest of geological mysteries.
What we know of dinosaurs we are forced to learn from fossils. Dinosaurs first appeared on this planet about 230 million years ago during a time period geologists call the Triassic. They lived happily until 65 million years ago at the end of the Cretaceous period when they were wiped out by a catastrophe of unimaginable proportions. When they died, the Cretaceous period died, too, and the Tertiary period began. Thus, the time of the dinosaur extinction is referred to as the Cretaceous-Tertiary, or K-T, boundary (K is used for Cretaceous because an earlier period, the Cambrian, is abbreviated as C). What caused the extinction of the dinosaurs and how it occurred is an important question not only for geologists and people who like dinosaurs but for all scientists concerned with the evolution of life. In order to answer this question, we need to look at just what happened 65 million years ago.
The dinosaurs werent the only animals to go extinct 65 million years ago, lots of others were killed off, too. In fact about 70% of all life on this planet was killed off; lots of plants, land animals, and sea creatures became extinct, too. The K-T boundary is important because it represents the time of this great extinction. Naturally, geologists would like to see the rocks from this time in order to look for possible clues to what killed everything off. Luckily there are places on this planet where you can actually put your finger on the layer of rock that has dinosaurs below it and no dinosaurs above it. This is the K-T boundary, the rock deposited at the time when the dinosaurs went extinct. The actual layer in rock is less then an inch thick and can be found all over the world. What makes the K-T boundary special is that the rock layer actually contains clues that have helped explain what killed the dinosaurs.
Before 1980, many people had ideas about what killed the dinosaurs, but no one had an idea that could actually be tested. In 1980, a team of scientists from California proposed (in what is known as the Alvarez theory, named after two of the scientists) that a large meteorite hit the earth precisely 65 million years ago and killed off the dinosaurs and everything else. Their statement was unique in that, if it was true, it would be possible to test the K-T boundary around the globe and look for evidence of a meteorite. Meteorites are unusual in that they contain metals not commonly found on this earth. One such metal is iridium, a metal much like platinum.
What the Alvarez group of scientists found in the K-T boundary in Italy was a lot of iridium, precisely at the rock layer that marks the boundary. Because they found so much iridium in the boundary layer, they reasoned that it could only have come from a meteorite, and a big one at that. If a big meteorite had hit the earth at the K-T boundary, then surely it must have done a lot of damage and could have killed off the dinosaurs. The Alvarez team estimated that the meteorite that hit the earth was about six miles wide, the size of Mount Everest!
The explosion from this meteorite made the loudest sound that was ever heard in our solar system. Too bad we werent around to hear it. Unfortunately for the dinosaurs, and a lot of other animals, they did hear it, and they didnt survive. The explosion from the meteorite hitting the earth, off the coast of Mexico as we now know, sent vast clouds of dust into the air. The dust blocked the light from the sun and made the whole world very cold for a long time. With no sunlight, lots of the plants died; with no plants, the animals that ate plants died; the animals that ate the animals that ate plants also died and so onuntil 70% of everything was dead.
The K-T boundary exists around the world but has never been found in the Denver Basin. We hope to find the actual layer that contains the metals from the meteorite in the Kiowa core and a promising portion of the core has been identified. Were currently waiting for tests to be run on that part of the core, one of which looks for Iridium, and hope to know more soon.