The Milankovitch curve involves three cycles: the eccentric orbit of the Earth around the Sun with a cycle of about 100,000 years; the precession of the equinoxes with a cycle of about 22,000 years; and the axis tilt variation with a cycle of about 40,000 years. I thought the precession and the tilt were one and the same, but there are apparently two different processes here. I think the high and low part of the curves approximately match up to the glaciations, but I'm not sure.
Ice cores taken from the floor of the ocean and based on the ratio of oxygen 18 to oxygen 16--the ratio increases during colder periods--show five glaciations during the last 450,000 years or an average of one per 90,000 years and the cores also show that were probably 30+ glaciations during the past 3,000,000 years or so. Three millions years represents the approximate beginning of the ice age, which we are still in. One of the strongest arguments for the ice age is the movement of the continents up and around the Artic Circle. Three million years ago was approximately the time that the ice caps and sheets began forming.
I know there is confusion about the term "ice Age," but I prefer the term "glaciation" when referring to the growth and retreating of the glaciers that occurred so often during the last 3,000,000 years.
I don't know if this information helps or not, and I forget what the original argument was; however, I don't feel that name calling and the exchange of negative strokes helps, nor is it consistent with the nature of this website. We've all ready had one website,i.e., Abuzz (RIP) succumb due to the excesses of its members.
I think this is an excellent thread, and I wish we had more participants.
coluber2001 wrote: I think this is an excellent thread, and I wish we had more participants.
I agree, coluber, and I wanna say you've offered some valuable posts here. I think perhaps sometimes members see a few typically outrageous wingnut/fringie comments on the first few pages they come to on a thread such as this and decide all is best if they simply pass it by - avoiding irritation.
Thanks, Timberlandko. I'm still not sure about the Milankovitch curve. Perhaps, you can help me there. I know it represents the fluctuating insolution intensity, and that the Earth's eccentric orbit around the Sun is one variable, but the tilt of the Earth is what confuses me. I have a geography book that claims that the tilt has a cycle of 40,000 years, which is at odd with the precession, which is 26,000 years. Some else, I read that the curves synchronize every 40,000 years because of the precession and the eccentric orbit. Another source claims that there is an extra variation in the tilt of 40,000 years on top of the precession. It's all very confusing.
The subject of the Pleistocene extinctions is of great interest to me, and I think that the old and widely accepted theory of overhunting of the prey animals just doesn't seem viable to me. What do you think?
Thanks, Timberlandko. I'm still not sure about the Milankovitch curve. Perhaps, you can help me there. I know it represents the fluctuating insolution intensity, and that the Earth's eccentric orbit around the Sun is one variable, but the tilt of the Earth is what confuses me. I have a geography book that claims that the tilt has a cycle of 40,000 years, which is at odd with the precession, which is 26,000 years. Somewhere else, I read that the curves synchronize every 40,000 years because of the precession and the eccentric orbit. Another source claims that there is an extra variation in the tilt of 40,000 years on top of the precession. It's all very confusing.
The subject of the Pleistocene extinctions is of great interest to me, and I think that the old and widely accepted theory of overhunting of the prey animals just doesn't seem viable to me. What do you think?
@rosborne979,
I take it for a grain of salt now. Most people are morons. These aren't the Oliver Cromwell revolutionaries.
These are people that want a paper written and their name acknowledged, and that is about it. That goes the same for some of the crummy threads in here on the Neanderthals.
All we know about Neanderthals is the same as what they knew in the 1840s. That they were another species of human. Everything else is just flapping your gums. Whether or not they liked dense shade. Did they eat squash. I was sitting in a hotel lobby once and watched that dumb show Ancient Aliens, and they actually did a whole forty five minute show about how they think that dragons were real creatures. The flying kind that were as large as a house. And no they weren't saying Pteradactyls or that they were mistaken dinosaurs.
Mammoths were basically the same as elephants. Based on the "excellent" reasoning of coluber2001 then Elephants should be extinct.
Did the mammoths eat garlic? I thought some of them survived on Wrangel island.
