Relative dating

Question 1

What is stratigraphy?

Answer 1

Is the study of layers or strata.

Question 2

What are the 2 ways in which stratigraphy can be useful in dating fossil material?

Answer 2

1. Principle of superposition.
2. Correlation of rock strata.

Question 3

What is the principle of superposition?

Answer 3

This principle assumes that the layers of sedimentary rock at the top are younger than those at the bottom.

Question 4

Why should you be cautious when applying the principle of superposition?

Answer 4

1. The sequence of rock may be turned upside down.
2. Animals or humans could have buried fossils or artefacts after the deposition of soil and the specimen may be younger than some layers above it.

Question 5

What is the correlation of rock strata?

Answer 5

The correlation of rock strata matches layers of rock from different areas. Matching rocks can be done by studying the layer or fossils contained within them.

Question 6

What are index fossils?

Answer 6

Index fossils are easily recognisable and were widely distributed and were present for a short length of time. Index fossils make correlation more precise. They are also useful to provide an idea of the type of climate at the time.

Question 7

What can fossilised pollens as index fossils be useful for?

Answer 7

As they can construct a picture of the type of vegetation existing at that time.

Question 8

What is fluorine dating?

Answer 8

Is used on the basis that when a bone is left in soil fluoride ions in water replace some of the ions in the bone. The older the fossil the more fluoride it should contain. The concentration of fluoride varies from place tp place.

Question 9

What are the two major problems with the fossil record?

Answer 9

1. The fossil record is not complete.
2. Fossils that are found can be problematic.

Question 10

What are 6 points why the fossil record is not complete?

Answer 10

1. Fossilisation occurs irregularly.
2. Conditions for fossilisation do not always occur.
3. Organsims were not preserved.
4. Only a small number of fossils have been discovered.
5. Human activity destroyed fossils.
6. Buried too deep.

Question 11

What are 3 points why fossils that are found can be problematic?

Answer 11

1. Carbon dating must contain carbon and the material can only be dated back to 60,000 years.
2. Potassium-argon dating relies on volcanic lava present.
3. It is unusual to find a fossil of an entire organsim.

Question 12

What are the 4 conditions required for fossilisation to occur?

Answer 12

1. A quick burial of the material.
2. The presence of hard body parts.
3. An absence of decay organisms.
4. A long period of stability. The organism needs to be left undisturbed.