Question

Which one of the following observations is consistent with the solid nature of the Earth's mantle?

• A. S waves propagate through the mantle
• B. S waves do not propagate through the mantle
• C. P waves propagate through the mantle
• D. P waves are refracted in the mantle

Hint:

S waves cannot travel through liquids, which is why they do not propagate through the Earth's outer core but can propagate through the solid mantle.

Answer 1

The Correct Option is A

Step 1: The two wave types.
Earthquakes send out P waves and S waves. P waves can pass through both solids and liquids, but S waves can pass through solids only.

Step 2: Why S waves are the key test.
Since S waves need a solid to travel, finding them in a layer proves that layer is solid. They simply stop in any liquid.

Step 3: Apply it to the mantle.
Observations show that S waves do travel through the whole mantle. That can only happen if the mantle behaves as a solid.

Step 4: Compare with the P wave options.
P waves passing through, or being bent in the mantle, would happen whether the mantle were solid or liquid. So those facts do not by themselves prove a solid mantle.

Step 5: Final choice.
The observation that fits a solid mantle is that S waves do propagate through it.
\[ \boxed{\text{S waves propagate through the mantle}} \]