Question

instructions: read the information below and then answer the questions about the rocks. when new rock is created from magma, it contains minerals such as magnetite that align with and point to the earths magnetic north pole before they cool and harden. this information becomes locked into the rocks. every 300,000 years (on average) the magnetism of the earths flips. the pattern of magnetic flips is identical on both sides of the mid - atlantic ridge, as seen in the diagram below. age of the rock (mya) 4 3 2 1 mid - ocean ridge indicates a normal magnetic field (same as todays) on earth indicates a reversed magnetic field (opposite n/s) on earth 1. fill in the rock age on the right side of the ridge. 2. which of the four rock samples is the oldest? 3. what would be the approximate age (in mya) of rock c? 4. describe two differences in rocks a and b. 5. describe two similarities of rocks b and c.

Explanation:

Step1: Identify rock - age pattern

The age of rocks increases as we move away from the mid - ocean ridge. The pattern on the left side can be mirrored to the right side.

Step2: Determine the oldest rock

The rock farthest from the mid - ocean ridge is the oldest. Among A, B, C, and D, rock D is the farthest.

Step3: Estimate rock C's age

Rock C is approximately 1.5 mya as it is between the 1 mya and 2 mya marks.

Step4: Find differences between A and B

Rock A has a reversed magnetic field while B has a normal magnetic field. Also, rock A is older than rock B.

Step5: Find similarities between B and C

Both B and C have a normal magnetic field. Also, they are relatively close in age compared to the overall age range of the rocks shown.

Answer:

1. The rock ages on the right side mirror the left side. Starting from the ridge and moving outwards, they are 1 mya, 2 mya, 3 mya, 4 mya etc.
2. D
3. 1.5 mya
4. Rock A has a reversed magnetic field and is older than rock B which has a normal magnetic field.
5. Both have a normal magnetic field and are relatively close in age.