Unit 27: Planet Earth in Profile: The Layered Interior
1) What evidence helps scientists understand the physical properties of Earth’s internal
structure?
a) earth’s density
b) earthquake activity *
c) volcanic activity
d) atmospheric composition
2) Earthquakes release energy in the form of:
a) seismic waves *
b) radiation waves
c) propagation waves
d) mechanical waves
3) Earthquakes that occur in the Northern Hemisphere can be recorded by seismographs
in the Southern Hemisphere.
a) True*
b) False
4) What determines the speed of seismic waves?
a) type of wave
b) density of the material it is passing through
c) weather conditions
d) both (a) and (b)*
5) If a strong earthquake occurred at the North Pole (0 degrees North), P waves:
a) can be found at any seismic station around the globe
b) are not found at angles greater than 103 degrees
c) are not received over a large shadow zone between approximately 103 to 142
degree angles from the source of the earthquake *
d) are not found at angles less than 142 degrees
6) A type of body wave that moves at right angles to the direction of the travelling wave is
called:
a) p-waves
b) s-waves *
c) surface waves
d) propagation waves
7) Waves that travel through solids only are typically _____ waves.
a) p
b) s *
c) surface
d) propagation
8) Earth’s internal layer that is composed mostly of iron (Fe) and Magnesium (Mg) that is
mostly solid with a thin layer of partially molten rock is called the:
a) inner core
b) outer core
c) mantle *
d) crust
9) The internal layer of the Earth that is responsible for allowing the lithospheric plates to
move along the surface is the:
a) liquid outer core
b) asthenosphere *
c) hydrosphere
d) oceanic crust
10) The Mohorovicic discontinuity or Moho is:
a) a sharp density change in Earth’s interior
b) a contact plane between the crust and mantle
c) helps scientists determine the thickness of Earth’s crust
d) all of the above *
11) Which statements best describe the features of Earth’s continental crust?
a) Continental landmasses have the lowest densities and may sometimes float over
denser material
b) Composed mostly of felsic rocks
c) Feldspar is a common mineral found along Earth’s crust
d) all of the above*
12) Which statement best describes the features of Earth’s oceanic crust?
a) higher density
b) dark, mafic rock
c) usually dark colored
d) all of the above *
13) It is difficult to directly observe the internal structures of our Earth, yet we understand
many of its physical and chemical properties. One way to understand the chemical
properties of the Earth is by calculating the mass and size of the Earth. The average
density of the Earth is 5.5 g/cm3; whereas the average density of the continental crust is
2.7 g/cm3 and oceanic crust is 3.3 g/cm3. Which statement best explains the
discrepancy between the densities of the Earth’s crust versus the overall average?
a) the deeper layers of the Earth are made up of heavier elements such as iron, nickel,
and magnesium *
b) the sun’s effect on the density of the Earth’s crust has not been calculated
c) these numbers change with every earthquake occurrence
d) adding the moon’s density to the density of the continental and oceanic crusts adds
up to Earth’s average density