A cross section of Earth reveals a layered structure that has different thicknesses and densities. How do geologists know this?
A)From drilling and digging down into the various layers
B)From observing the characteristics of lava and gas issuing from volcanic vents
C)From observing the transit times through Earth of waves generated by earthquakes
D)From comparisons with drill cores taken by robot spacecraft on Mars and Venus

Question

Quizplus · Accepted Answer

Geologists know the layered structure of Earth from observing the transit times through Earth of waves generated by earthquakes. The waves travel at different speeds through different types of material, allowing geologists to determine the depth and composition of various layers within the Earth.

A Cross Section of Earth Reveals a Layered Structure That