chapter 4 test review

chapter 4 test review

• 4.1

• INSIDE EARTH

• S and P waves- How do they travel?

S and P waves

• • P-waves (primary waves) are fastest, traveling at about 6 to 7 kilometers (about 4 miles) per second, so

  they arrive first at the seismometer. P-waves move in a compression/expansion type motion, squeezing and

  unsqueezing earth materials as they travel. This produces a change in volume for the material. P-waves bend

  slightly when they travel from one layer into another. Seismic waves move faster through denser or more rigid

  material. As P-waves encounter the liquid outer core, which is less rigid than the mantle, they slow down.

  This makes the P-waves arrive later and further away than would be expected. The result is a P-wave shadow

  zone. No P-waves are picked up at seismographs

• • S-waves (secondary waves) are about half as fast as P-waves, traveling at about 3.5 km (2 miles) per second,

  and arrive second at seismographs. S-waves move in an up and down motion perpendicular to the direction of

  wave travel. This produces a change in shape for the earth materials they move through. Only solids resist a

  change in shape, so S-waves are only able to propagate through solids. S-waves cannot travel through liquid.

• 
  

S and P waves

• By tracking seismic waves, scientists have learned what makes up the planet’s interior (Figure 4.2).

  • P-waves slow down at the mantle core boundary, so we know the outer core is less rigid than the mantle.

  • S-waves disappear at the mantle core boundary, so the outer core is liquid.

• 
  

Multiple Choice

1. Scientists know about Earth’s interior by studying evidence from

• meteorites.

• . seismic waves.

• magnets

• corn

mantle

• Heat flows in two different ways within the Earth:

  1. Conduction: Heat is transferred through rapid collisions of atoms, which can only happen if the material is

  solid. Heat flows from warmer to cooler places until all are the same temperature. The mantle is hot mostly

  because of heat conducted from the core.

  .

• 2. Convection: If a material is able to move, even if it moves very slowly, convection currents can form

Earth's Core

• At the planet’s center lies a dense metallic core. Scientists know that the core is metal because:

• 1. The density of Earth’s surface layers is much less than the overall density of the planet, as calculated from

  the planet’s rotation. If the surface layers are less dense than average, then the interior must be denser than

  average. Calculations indicate that the core is about 85% iron metal with nickel metal making up much of the

  remaining 15%.

• 2. Metallic meteorites are thought to be representative of the core. The 85% iron/15% nickel calculation above

  is also seen in metallic meteorites

Multiple Choice

Earth is divided by composition into three layers( leave inner and outer off of this)

• true

• false

Multiple Choice

The mantle is heated mainly by heat conducted from the core.

• true

• false

Multiple Choice

. The outer core has a higher temperature than the inner core.

• true

• false

4.2- early earth