P waves moving through the base of continents move at about ________ km/sec, but once they cross the Moho, the velocity changes to ________ km/sec.

Question

Quizplus · Accepted Answer

P waves move at a faster velocity through the solid interior of the Earth (about 6-8 km/sec), including the base of continents. However, once they reach the boundary between the crust and the mantle (the Moho), the velocity changes and slows down to about 4 km/sec. This change in velocity is due to the difference in density and composition between the two layers. Therefore, the best choice for the given velocities is C.

P Waves Moving Through the Base of Continents Move at About