how do fossils help them to compare the ages of rocks from different places?

Answer 1

Certain fossils known as index fossils have broad geographic distributions and short ranges. So, if you can find the same index fossil in rocks in (for example) North America and France, and you know that that species had a very short evolutionary lifespan (geologically speaking), you know that the rocks are roughly the same age.

Answer 2

To understand this, you should have a general idea about Index fossils. There were many plants and animals, once thrived on earth but are now extinct. Some of these species were very short-lived. At the same time their fossils can be morphologically very distinct to identify. This makes these fossils index fossil. In other words, a good index fossil marks certain geological age, when they were alive and kicking on earth. So a rock showing such a fossil definitely indicate its age to be of that period. For example advanced ammonites with complex ornament and suturing is typical of lower Devonian to upper Cretaceous age. So any sedimentary rock, from anywhere in the world hosting such a species of advanced ammonites will indicate its age of formation to be of that period. And similar fossil reported from rocks of another place will indicate an age correlation.

Answer 3

Fossils can't be used to determine the ages of rocks or anything else. The only thing a fossil can tell us is that the creature died. They can't even tell us whether that creature had kids or not. When God flooded the world about 4000 years ago (Gen 6:17), the flood would have distributed the deads bodies of animals and people etc. into different layers. This is known as hydrological sorting. This is why we find fossils in different layers of earth all over the world. For more info, go to this link http://www.drdino.com/downloads.php

Answer 4

They compare what is fossilized and compare to a database of what lived when. A more useful way to tell the age of a rock is to know what strata it lies in. Sometimes measurements of radiation can help.

Answer 5

You should note the circular reasoning.
Index fossils are used to date rocks. And rocks are used to date fossils.
All based on the uniformitarian assumption that the world is billiones of years old and evolution has occured.

So assume evolution and billions of years and .... lo and behold the evidence is used to support our assumption!.

Take a reality check - look at the evidence for yourself.

In fact there is much evidence that refutes vast age:
Radiometric dating is not what it is cracked up to be.
Very young volcanic rock has been dated as millions of years old. All coal (allegedly ancient) contains carbon 14 which should have dissipated in about 50000 years.
http://www.creationontheweb.com/content/view/3059/

How do you think these fossils formed in the first place? To make a fossil the animal/plant has to be buried very quickly - otherwise it gets eaten. It is very rare to see an animal buried whole. The fact that the whole world is covered in sedimentary rocks containing billions of fossils is evidence of the global flood.
http://www.creationontheweb.com/content/view/3001

Did you know they've found dinosuar bones with blood cells? Hardly 65 million years old !
http://www.googlesyndicatedsearch.com/u/creationontheweb?q=dino+blood&hl=en&lr=

Answer 6

There's an enigma about fossils. When a fish dies and sinks to the bottom of an ocean it rots quickly. The only way to have a fish in a rock is to back a cement truck up to your aquarium and fill it with concrete. The we have snails, the snail carbon dates to the present but its shell dates to several million years old. That's because the snail eats limestone to make its shell.
Also carbon dating from the land is differant from dating from the sea.