CSS - PMS - CCE - PCS - Geography
Earth's Shape and Structure
The lower mantle extends from about 660 km to:
A. 1,000 km
B. 1,500 km
C. 2,900 km
D. 5,150 km
Correct Answer: C
The lower mantle extends from around 660 km to the core-mantle boundary near 2,900 km.
CSS - PMS - CCE - PCS - Geography
Earth's Shape and Structure
The mantle transition zone lies approximately between:
A. 35 and 100 km
B. 100 and 250 km
C. 410 and 660 km
D. 2,900 and 5,150 km
Correct Answer: C
The mantle transition zone is roughly 410–660 km deep and contains major mineral phase changes.
CSS - PMS - CCE - PCS - Geography
Earth's Shape and Structure
The upper mantle extends approximately to a depth of:
A. 100 km
B. 410 km
C. 660 km
D. 2,900 km
Correct Answer: C
In modern geophysics, the upper mantle extends to about 660 km depth.
CSS - PMS - CCE - PCS - Geography
Earth's Shape and Structure
A rock commonly used as a model for upper-mantle composition is:
A. Peridotite
B. Sandstone
C. Shale
D. Marble
Correct Answer: A
Peridotite, rich in olivine and pyroxene, is representative of upper-mantle composition.
CSS - PMS - CCE - PCS - Geography
Earth's Shape and Structure
The mantle is composed mainly of:
A. Iron-nickel metal only
B. Magnesium- and iron-rich silicate rocks
C. Pure quartz
D. Water and ice
Correct Answer: B
The mantle is dominated by ultramafic silicate minerals rich in magnesium and iron.
CSS - PMS - CCE - PCS - Geography
Earth's Shape and Structure
The mantle extends from the Moho to a depth of about:
A. 660 km
B. 1,500 km
C. 2,900 km
D. 5,150 km
Correct Answer: C
The mantle extends to the core-mantle boundary at about 2,900 km depth.
CSS - PMS - CCE - PCS - Geography
Earth's Shape and Structure
The Moho was identified mainly through changes in:
A. Ocean salinity
B. Seismic wave velocities
C. Atmospheric pressure
D. Magnetic declination only
Correct Answer: B
A sudden increase in seismic-wave speed revealed a boundary between crust and mantle.
CSS - PMS - CCE - PCS - Geography
Earth's Shape and Structure
The Mohorovičić discontinuity is commonly shortened to:
A. Moho
B. Guten
C. Lehman
D. Repetti
Correct Answer: A
The crust-mantle boundary is commonly known as the Moho.
CSS - PMS - CCE - PCS - Geography
Earth's Shape and Structure
The boundary between the Earth's crust and mantle is called the:
A. Gutenberg discontinuity
B. Mohorovičić discontinuity
C. Lehmann discontinuity
D. Conrad discontinuity
Correct Answer: B
The Mohorovičić discontinuity, or Moho, separates the crust from the mantle.
CSS - PMS - CCE - PCS - Geography
Earth's Shape and Structure
The average density of the Earth as a whole is approximately:
A. 2.0 g/cm³
B. 3.3 g/cm³
C. 5.5 g/cm³
D. 9.5 g/cm³
Correct Answer: C
Earth's mean density is about 5.51 g/cm³, indicating a dense metallic interior.
CSS - PMS - CCE - PCS - Geography
Earth's Shape and Structure
The average density of continental crust is about:
A. 1.0 g/cm³
B. 2.7 g/cm³
C. 5.5 g/cm³
D. 11.0 g/cm³
Correct Answer: B
Continental crust has an average density near 2.7 g/cm³.
CSS - PMS - CCE - PCS - Geography
Earth's Shape and Structure
Continental crust is generally more:
A. Mafic and dense than oceanic crust
B. Felsic and less dense than oceanic crust
C. Metallic than the mantle
D. Uniform than oceanic crust
Correct Answer: B
Continental crust is more felsic and generally less dense than oceanic crust.
CSS - PMS - CCE - PCS - Geography
Earth's Shape and Structure
Oceanic crust is mainly composed of:
A. Basaltic rocks
B. Granite only
C. Limestone only
D. Coal-bearing rocks
Correct Answer: A
Oceanic crust is dominantly basaltic at the surface with gabbro at depth.
CSS - PMS - CCE - PCS - Geography
Earth's Shape and Structure
Average continental crust is roughly:
A. 5 km thick
B. 15 km thick
C. 35 km thick
D. 100 km thick
Correct Answer: C
Continental crust averages around 35 km thick and may exceed 60–70 km beneath mountains.
CSS - PMS - CCE - PCS - Geography
Earth's Shape and Structure
Typical oceanic crust is approximately:
A. 5–10 km thick
B. 20–30 km thick
C. 40–50 km thick
D. 80–100 km thick
Correct Answer: A
Oceanic crust is relatively thin, generally about 5–10 km thick.
CSS - PMS - CCE - PCS - Geography
Earth's Shape and Structure
The crust is thickest beneath:
A. Deep ocean basins
B. Mid-ocean ridges
C. Major mountain ranges
D. Ocean trenches only
Correct Answer: C
Continental crust is especially thick beneath major mountain belts.
CSS - PMS - CCE - PCS - Geography
Earth's Shape and Structure
The Earth's three main compositional layers are:
A. Lithosphere, asthenosphere, mesosphere
B. Crust, mantle, core
C. Troposphere, stratosphere, mesosphere
D. Sial, sima, magma
Correct Answer: B
By composition, Earth is divided into crust, mantle and core.
CSS - PMS - CCE - PCS - Geography
Earth's Shape and Structure
The Earth's outermost solid layer is the:
A. Mantle
B. Crust
C. Outer core
D. Asthenosphere
Correct Answer: B
The crust is the Earth's outermost compositional layer.
CSS - PMS - CCE - PCS - Geography
Earth's Shape and Structure
Which feature makes the geoid irregular?
A. Variations in Earth's gravity field
B. Earth's orbit alone
C. Uniform density everywhere
D. Constant atmospheric pressure
Correct Answer: A
Uneven mass distribution causes spatial gravity variations, producing an irregular geoid.
CSS - PMS - CCE - PCS - Geography
Earth's Shape and Structure
The geoid most closely corresponds to:
A. Mean sea level extended beneath continents
B. Top of the atmosphere
C. Base of the crust
D. Outer core surface
Correct Answer: A
The geoid approximates global mean sea level continued beneath the continents.