ESCI Chap 12

conduction

the flow of heat through a material -heat conducts in two ways 1. through the collisions of atoms 2. through the flow of electrons

What is the average density of continental crust?

2.7 g/cm3

P waves cannot penetrate the outer core because it is liquid. T/F

false

As of 2015, what was the deepest drill core yet taken that allowed scientists to study the Earth's interior?

12.3 km

Why is the Earth hot? Where does the heat come from?

-Earth has experienced two thermal stages 1. 1st occurred during Earth's formation and lasted about 50 million years and involved a rapid increase in internal temperature 2. 2nd stage has been a very slow process of cooling over the remaining 4.5 billion years of Earth history -several factors contributed 1. Earth formed through collisions of countless planetesimals ("baby planets"), with each collision, the kinetic energy of motion was converted into thermal energy 2. Earth contained many short-lived radioactive isotopes, such as aluminum-26 and calcium-41. As these isotopes decayed to stable forms, they released a great deal of energy, called radiogenic heat. 3. collision of a Mars-sized object with Earth that led to the formation of the Moon -Heat travels from Earth's interior by: convection, conduction, and radiation.

How do we study the interior of the Earth? How do we know what it is made of and how those materials behave? (pg. 366)

-seismic waves -

Briefly explain the processes by which the Earth became differentiated into layers. (pg. 364)

-the high-velocity impact of nebular debris and the decay of radioactive elements caused the temperature of our planet to steadily increase -earth became hot -elements including iron and nickel began to melt -melting produced liquid blobs of heavy metal that gravitationally sank toward the center of the planet -this produced Earth's dense iron-rich core -early period of heating resulted in another process of chemical differentiation, whereby melting formed masses of less-dense, molten rock that buoyantly rose toward the surface and solidified to produce a primitive crust

What is the average density of oceanic crust?

3.0 g/cm3

What is the average thickness of the oceanic crust?

7 km

What causes the Earth's magnetic field? Why is it important? What are magnetic reversals?

As iron-rich fluid in the outer core rises, its path becomes twisted because of Earth's rotation. As a result, the fluid moves in spiraling columns that align with Earth's axis of rotation. Because this iron-rich fluid is electrically charged and flowing, it generates a magnetic field- a phenomenon called geodynamo. -it sustains life on Earth -keeps us from being exposed to high amounts of radiation from the sun

What is thought to produce Earth's magnetic field? A. As iron-rich fluid in the liquid inner core rises, the fluid is twisted by Earth's revolution around the Sun. The flow of this electrically charged material generates a geodynamo. B. 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. C. As iron-rich fluid in the liquid inner core and outer core rises, the fluid is twisted by Earth's rotation. The flow of this electrically charged material generates a geodynamo. D. As iron-rich fluid in the liquid outer core rises, the fluid is twisted by Earth's revolution around the Sun. The flow of this electrically charged material generates a geodynamo. E. As iron-rich fluid in the liquid inner core rises, the fluid is twisted by Earth's rotation. The flow of this electrically charged material generates a geodynamo.

B. 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.

Which process is responsible for Earth's magnetic field? In which layer does this process occur?

Convection; outer core

How was layering produced during the formation of Earth? A. During Earth's formation, the elements nickel, iron, silicon, and aluminum all originated in Earth's outermost layer. The silicon and aluminum remained in this layer and formed a primitive crust, whereas the nickel and iron sank down to the center of Earth in response to gravity, creating its core. B. During Earth's formation, iron, nickel, and other dense elements such as uranium remained at Earth's surface to create Earth's primitive crust. Meanwhile, less dense oxygen-seeking elements such as silicon and aluminum sank to the center of Earth, producing its core. C. During Earth's formation, iron, nickel, and other dense elements such as uranium rose to Earth's surface to create Earth's primitive crust. Meanwhile, less dense oxygen-seeking elements such as silicon and aluminum sank to the center of Earth, producing its core. D. During its formation, Earth was so hot that iron, nickel, and other dense elements such as uranium melted and quickly sank to the center of Earth, producing its core. Meanwhile, less dense oxygen-seeking elements such as silicon and aluminum remained in place to create Earth's primitive crust. E. During its formation, Earth was so hot that iron, nickel, and other dense elements such as uranium melted and quickly sank to the center of Earth, producing its core. Meanwhile, less dense oxygen-seeking elements such as silicon and aluminum rose to create Earth's primitive crust.

E. During its formation, Earth was so hot that iron, nickel, and other dense elements such as uranium melted and quickly sank to the center of Earth, producing its core. Meanwhile, less dense oxygen-seeking elements such as silicon and aluminum rose to create Earth's primitive crust.

What materials make up Earth's core?

Iron and nickel

Which layer of Earth makes up more than 82 percent of the volume of the planet?

Mantle

What are P and S waves? How are they different?

P and S waves are earthquake waves used to study Earth's interior -S waves do not travel through liquids

What is the primary method scientists use to determine the layering of the interior of the Earth?

Seismic waves

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.

In general, how does temperature change between Earth's surface and its core?

The temperature increases from Earth's crust to its core; the rate of increase changes within and between Earth's layers.

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.

A ________ occurs when an iron-rich fluid in the core is electrically charged and flowing, which generates a magnetic field.

geodynamo

convection

the transfer of heat in a fluid-like manner, where hot materials displace cooler materials (or vice versa)