Basically, some scientists...their names arent important, theyre old people , they came across this layer of rock in the earth. In the geologic record, its a layer that is about 65 million years old. It seperates the Cretaceous (K) from your tertiary (T). Cretaceous and Tertiary are...geologic names assigned to rocks of particular ages.
If you examine fossils within the earth, what you will find are a vast variety of fossils, all sorts of dinosaurs and mammals and sea critters and such. But right above that rock layer, above the K-T boundary, all life (not all but a large percentage) just kind of disappears.
See, if you see the green color, you have the cretaceous. Tertiary isn't labeled on this particular diagram, but i liked this one because it had nice pictures . U can also see the Silurian there in purple in between 400-450 million years ago, for those of you who have taken notice of my account name.
Anyway...the boundary between the Cretaceous and the Paleogene/Cenozoic/Tertiary, the boundary consists of a rare earth known as iridium. And, the K-T layer can be found in various locations around the world.
Iridium, is a prominent element found in meteorites. So, people began to wonder, well, is this global layer of iridium the result of a meteorite impact?
So scientists ran around to see what else they could learn about the K-T rocks, what they found were things like...heavily burned soils. And melted rock fragments. With use of physics, it can be seen that something with immense energy essentially turned rocks instantaneously into molten rock. And that molten rock cools off in very recognizable ways. It shears and gets stretched and...yea. Its called shocked quartz.
So, now we have scientists with a handful of evidence. Then later on, in todays time and more recently, a handful of meteorite craters have been discovered that actually are roughly of the same age (65 mya) as the iridium layer (chuxulub crater). Right. So this is why you have people saying that dinosaurs were wiped out by an asteroid or asteroids.
On top of that, on the other side of the world, the Deccan Traps, which are these...massive basalt beds, basically show us that extreme vulcanism at roughly the same time as the K-T impact and all the evidence that followed.
So, here is a brief overview for those who may be interested in what some geologists spend their time doing. And it also holds a lot of implications to religious thought, for those who enjoy contemplating these things.
Oh, and one more thing, once the dinosaurs were not gobbling up our ancestors, it finally allowed mammals to proliferate around the world, and to become the dominant world rulers that we are today.
So, it means a lot if you think about it.
Thats my 2 second overview, i hope everyone enjoys and feel free to ask questions if you have any.
Edited by iSilurian, 10 December 2011 - 01:05 AM.