evolution question(s)

[Pauliesonne]

1. How do they date fossils?

2. Where's the most up-to-date site to learn more?

 

[Strider1974]

1/ The age of rocks around a fossil can be considered
2/ Mathematical calculations are used
3/ The state of decay, carbon-14, and isotopes figure in calculations
4/ Tree of life relationships often help sort the dates



http://www.actionbioscience.org/evolution/benton.html

 

[Apex Rogers]

A good place to start might be Talk Origins.

http://www.talkorigins.org/origins/faqs.html

 

[blutoski]

1. How do they date fossils?

2. Where's the most up-to-date site to learn more?

1. Depends on the fossil. Usually, the fossils are dated based on their strata location. The strata are usually dated as part of an interlocking series of findings involving radiometrics, magnetic vectors, uniformitarian assumptions about deposition rates, &c.

I observe that one of the previous posters suggested that carbon14 dating may be employed, but this is not the case for fossils, since they rarely contain original organic material. The strata above and below may have been dated with radiometrics, however, and common isotopes are argon and lithium. Even if the fossils contained organic material, Li/Ar isotopes also have much longer half-lives than C14 and are appropriate for these longer time periods.

2. talk.origins is an excellent resource

 

[CaveDave]

I observe that one of the previous posters suggested that carbon14 dating may be employed, but this is not the case for fossils, since they rarely contain original organic material.

AIUI, *fossils* include such materials as ivory, bone and amber, all of which contain carbon and most of their original organic structure, which may be young enough to be carbon-dated. Also, there are other, more long-lived elements present (as you mentioned) which may be used for age determination.

I suspect that you may have (as I once did ) confused fossilisation with *petrification* or *petrifaction* which is defined as:
petrifaction
n 1: the process of turning some plant material into stone by
infiltration with water carrying mineral particles
without changing the original shape [syn: {petrification}]
2: a rock created by petrifaction; an organic object
infiltrated with mineral matter and preserved in its
original form

HTH

Cheers,
Dave

ETA: Two (stupidly) omitted clauses.

 

[blutoski]

AIUI, *fossils* include such materials as ivory, bone and amber, all of which contain carbon and most of their original organic structure, which may be young enough to be carbon-dated. Also, there are other, more long-lived elements present (as you mentioned) which may be used for age determination.

I suspect that you may have (as I once did ) confused fossilisation with *petrification* or *petrifaction* which is defined as:
petrifaction
n 1: the process of turning some plant material into stone by
infiltration with water carrying mineral particles
without changing the original shape [syn: {petrification}]
2: a rock created by petrifaction; an organic object
infiltrated with mineral matter and preserved in its
original form

HTH

Cheers,
Dave

ETA: Two (stupidly) omitted clauses.

Duly noted, but I was responding in the spirit of the usual motive for the question. Most antievolution hoopla focuses on hominoid genera fossils, which are usually petrified.