Question

question 10(multiple choice worth 6 points)
(03.03 mc)
during an earthquake, scientists at a seismic station observed that some waves were detected earlier than others. what is the likely cause of this observation?
uniform pressure inside earth made the waves move at the same speed.
uniform temperature inside earth made the waves move at different speeds.
variation in density inside earth made the waves move at different speeds.
variation in temperature inside earth made the waves move at the same speed.

Explanation:

Earth's interior has varying densities. Seismic waves (like P - waves and S - waves) have different speeds. P - waves (primary) are faster and can move through solids, liquids, and gases. S - waves (secondary) are slower and only through solids. Density variations affect wave speeds. Uniform pressure/temperature would not cause speed differences. Variation in temperature causing same speed is incorrect as temperature affects wave speeds.

Answer:

Variation in density inside Earth made the waves move at different speeds.