yak said:
From what I read fossils are dated by the dirt they are found in and the dirt is dated by what fossil is found in them, aka circular reasoning.
You certainly haven't read that in any geology textbooks or published papers. If you are going to learn about geology, the best place to start is introductory geology textbooks rather than creationist propaganda designed to tell people who know little about the subject what they want to hear.
First of all, there is a minor technicality to address. Dirt is not necessarily synonymous with the sediments that comprise the bedrock.
The sedimentary bedrock, however, is not dated so that eliminates the "circular reasoning" charge right off the bat. Sedimentary rock is comprised of material eroded from pre-existing rocks. Using a radiometric dating method on sedimentary rocks would not give a date of the deposition of the rock, but rather would give a date of the formation of the initial material that was weathered and eroded to form the sediment that encases the fossil. So really, dating the sedimentary rock would give a date much older than the actual age of the sedimentary rock.
The cases where fossils are used to date the rock is when we already know the age of those fossils which are restricted to relatively short, diagnostic intervals of the geologic timescale.
Radiometric dating works in conjunction with basic geologic principles of relative dating. Radiometric dating is used to date igneous materials such as volcanic ash layers. The law of superposition states that in a vertical column of layered sediments, the top is the youngest and the bottom is the oldest. It's similar to the way one makes a layer cake where the bottom layer is deposited first, then the middle layer(s) in succession, and finally the top layer last. If you have sediments bound by ash layers, the bottom ash layer will give an older radiometric date than the next higher one. Thus you have an interval of time in between those two layers that represents the deposition of the sedimentary rock in between in which there are fossils. Thus we know the age of the fossils. That was a little longwinded, but hopefully clear.
Also no complete column has been found in the world.
Not only is that false, it is irrelevant. Whether or not a complete sedimentary column is found does not negate anything about modern geology nor does it negate the fact that segments can be correlated over diverse geographic areas.
Carbon dating, uranium dating, etc are not even 80% accurate.
That's false as well. Frequently the precision and accuracy of the measurements are in excess of 95%. Furthermore, carbon dating is used on organic material and is not used to date geologic features or for the age of the earth. It is only useful, with the best available technology, for the past 50 kyr, maximum. Many dating methods exist, however, including (but not limited to) K-Ar, Rb-Sr, Sm-Nd, and others. They do verify the dates of other methods as well despite involving different nuclides with different half lives. I'd say that's pretty accurate.
It has to be redone until the answer you desire comes out.
That's just plain false. In fact, anomalous dates can cause geologists to change how boundaries in the geologic timescale are defined. Dates aren't simply thrown out because it's not what people want to hear. Often times, anomalous dates are due to contamination. It is true, however, that estimates of dates are needed to determine which method to use. We can also identify problems by using other dating methods on the sample.
