Online Quiz 2 Flashcards
What is the approximate distance from the surface to the center of Earth?
6,400 km
The S-wave shadow zone extends from ____ to 180° angular distance from the earthquake focus.
105°
The S-wave shadow zone is larger than the P-wave shadow zone.
True
Which of the following seismic waves will arrive at a seismograph first?
P wave
Which layer in Earth does not transmit S waves?
the outer core
Where do P waves travel fastest?
lower mantle
Continental crust beneath mountains can be up to ___ kilometers thick.
100
How thick is the oceanic crust?
approximately 7 km
The oceanic crust consists mostly of
mafic rocks
Correctly list the three rock types in order of increasing P-wave velocity?
granite, gabbro, peridotite
The Moho marks the top of a partially molten layer
False
The crust is denser than the mantle
False
Which of the following marks the boundary between the crust and the mantle?
an increase in P-wave velocity and a change in rock type
How thick is average lithosphere?
100 km
The asthenosphere is stronger than the lithosphere
False
The boundary between the mantle and the core lies at a depth of approximately
3,000 km
What causes the sharp increases in the velocity of S waves at a depth of 400 and 660 km in the mantle?
changes in the mineral structures
At what depth does the transition from the upper mantle to the lower mantle occur?
approximately 400 to 600 kilometers
What element makes up most of Earth’s core?
iron
The inner core is solid and the outer core is liquid
True
Which of the following regions is hottest?
the inner core
Seismic wave speeds increase with
increasing density and decreasing temperature
Seismic tomography has revealed that seismic waves in the uppermost mantle are relatively
slow beneath mid-ocean ridges and fast beneath subduction zones
Where is Earth’s magnetic field generated?
in the outer core
Approximately how often does Earth’s magnetic field reverse itself?
every 500,000 years
Seismic waves that bounce off a boundary between two different materials are said to be ________, whereas seismic waves that cross the boundary and are bent are said to be ________.
reflected; refracted
S waves slow down as they travel through the mantle
False
The area on the surface of Earth where P waves and S waves are not recorded by seismograms following an earthquake event are referred to as
Shadow zones
A P wave that travels from the earthquake focus through the mantle, outer core, back through the mantle, and to Earth’s surface is labeled a
PKP wave
An S wave that is reflected once off the surface of Earth is labeled an ______ wave.
SS
The graphical curve that describes how temperature changes with depth in Earth is called the
geotherm
Earth’s magnetic field shields the surface of Earth from
solar winds
Earth’s inner core was discovered by seismologist
Inge Lehmann
In a deep mine, temperatures increase at the rate of approximately ______ per kilometer.
25°C
