which of these is (not) a guideline used to determine the relative age of rocks?

Question

(1) Volcanic rock is always older than sedimentary rock.

(2) Rocks of the same age often contain a similar mixture of fossils.

(3)Volcanic shafts are younger than the rock layers they cut through.

(4) older layers of sedimentary rock often lie below younger layers of sedimentary rock.


thank you....

Answer 1

The correct answer is 1.

Both volcanic and sedimentary rocks can be of any age, so they can not be used to determine relative age. There are sedimentary, igneous, and even some metamorphic rocks of all ages. The type of rock is not an indication of age - except banded iron formation, which must be 1.8 b.y. old or more.

2, 3, and 4 can all be considered as "True."

If you were awake in class and doing your own homework, the answers should have been obvious!

Answer 2

(1) Volcanic rock is always older than sedimentary rock
There is no age relationship between Volcanic and sedimentary rocks, either can be older or younger than the other even the structural relationship may not be a guide.

(2) Rocks of the same age often contain a similar mixture of fossils
True for sedimentary rocks but some fossils cover very large time periods so this too can be a trap for the inexperienced.

(3)Volcanic shafts are younger than the rock layers they cut through
This could be said to be generally true but there are exceptions as is the case for most rules.

(4) older layers of sedimentary rock often lie below younger layers of sedimentary rock
This also is generally true but there are exceptions as is the case for most rules.

Answer 3

1. Volcanic rock can be of any age relative to sedimentary.

Answer 4

1--there is no reason for volcanic rock to always be older than sedimentary rock.

Answer 5

(1)

Answer 6

1 is the best choice