SOLAR SYSTEM

Detailed explanation-1: -Rocks from inside Earth give geologists clues about Earth’s structure. Geologists have drilled holes as much as 12 kilometers into Earth. The drills bring up samples of rock. From these samples, geologists can learn about conditions deeps inside Earth, where these rocks formed.

Detailed explanation-2: -The structure of Earth’s deep interior cannot be studied directly. But geologists use seismic (earthquake) waves to determine the depths of Earth’s layers.

Detailed explanation-3: -These recordings made by a seismograph are called seismograms. Seismic waves travel at different speeds when they pass through different types of material, so by studying seismograms, scientists can learn a lot about Earth’s internal structure.

Detailed explanation-4: -Geologists use these records to establish the structure of Earth’s interior. The two principal types of seismic waves are P-waves (pressure; goes through liquid and solid) and S-waves (shear or secondary; goes only through solid-not through liquid).

Detailed explanation-5: -The types of waves that are useful for understanding Earth’s interior are called body waves, meaning that, unlike the surface waves on the ocean, they are transmitted through Earth materials. Imagine hitting a large block of strong rock (e.g., granite) with a heavy sledgehammer (Figure 9.3).