Mastering Geology: Chapter 12 Earth's Interior

What is thought to produce Earth's magnetic field?

As iron-rich fluid in the liquid outer core rises, the fluid is twisted by Earth's rotation. The flow of this electrically charged material generates a geodynamo.

Determine which type of heat transfer occurs in each layer or at each boundary. *convection, conduction, or both convection and conduction

Convection: Mantel Conduction: D'' layer inner core boundary between mantle and lithosphere Both convection and conduction: Outer core

Which of the following best describes the pattern of heat flow through the lithosphere?

Heat flow is high where crust is being created. (Ocean spreading centers are where new crust is being created, and have the highest heat flow.)

What seismic shadowing zone is visible in this image?

S-wave shadow

What is the Moho, and how is its depth determined?

The Moho is the boundary between the crust and the mantle. Its depth is determined by observing where refracted seismic waves and direct seismic waves cross over each other

Why is the asthenosphere weaker than the lithosphere?

The asthenosphere is warmer and has a lower viscosity than the lithosphere.

How do the positions of the magnetic poles change through time?

The magnetic north pole varies somewhat from the geographic North Pole while still remaining in the Northern Hemisphere. Additionally, periods of full magnetic reversals have occurred where magnetic north and magnetic south have switched places with each other. Both types of variation are caused by changes in the convection patterns within the outer core.

What characteristic of seismic waves makes them useful for probing Earth's interior?

The velocities and directions of seismic waves reliably differ when they encounter different materials within Earth.

What does a reflected wave tell us about Earth's interior?

The wave has hit a boundary between two different Earth materials, causing it to reflect back to Earth's surface.

Which of the following best describes what occurs during convection?

Warmer, less dense material rises.

What are the three compositionally distinct layers of Earth's interior?

a strong, rocky crust at Earth's surface, a hot, pressurized mantle beneath the crust, and an iron-rich core that is made of a solid inner core and a liquid outer core

Why do seismic waves travel along curved paths through the mantle?

because mineral phase changes in the upper mantle cause sudden increases in seismic velocity

The Moho separates the ______.

crust and mantle

One-third of Earth's mass comes from ______.

the core

What causes a mineral phase change?

the increase of pressure on a mineral when it is moved deeper within Earth