ERTH 111 MIDTERM 1 EXAM 2025
QUESTIONS AND ANSWERS
What is Physical geology/dynamic earth? - ANS The study of the processes of the Earth and
the composition
Scientific method: - ANS Hypothesis: a message expressing an opinion based on incomplete
evidence
Theory: scientific ideas supported by abundant evidence. passed many tests -failed none
Law: Statements that completely describe a specific relationship or phenomenon
Earths Formation; - ANS Initially homogeneous: all same parts
Differentiation event: Heat from collision + heat when matter starts to squeeze + heat from
decay of radioactive elements results in denser iron alloy separating out and lighter material
rising
present state of differentiation:
lithosphere/lithospheric motions
Earth's Interior - ANS Crust: (Oceanic and Continental):
Oceanic Crust: 7-10km thick. Top is a thin layer of clay and tiny shells.. beneath consists of
basalt and below that, gabbro
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, Continental Crust: - ANS 35-40km Thick. Rock type ranges from mafic to felsic. Continental
on average less mafic (felsic to intermediate composition) than oceanic, furthermore less
dense. Oxygen = most abundant
Mantle - ANS 2885 Km thick layer - largest part of earth. Consists entirely of ultramafic (dark
and dense) rock called peridotite, making peridotite most abundant rock on planet. Almost all
mantle is solid rock but its soft enough that it flows
Outer/Inner Core: - ANS Outer core: liquid iron alloy, this flow of iron alloy creates magnetic
field
Inner core: solid iron because of pressure
Gradients in Earth: - ANS Pressure and temperature both increase with depth in the Earth.
The rate at which temperature increases as depth increases is the geothermal gradient.
Sources of energy for the earth - ANS Interior: 80% of energy from decay of radioactive
elements
Exterior: Sun
Exterior Processes (Fast): - ANS Wind, weather, rivers, currents, glaciers
Interior (Slow): - ANS plate tectonics.. mountain building, earthquakes, landslides, volcanoes,
oceans open/close...
Continental vs. Oceanic crust (difference in thickness and composition) vs. Mantle
Continental 35-40km thick, oceanic 7-10km... Continental more felsic/intermediate, less dense..
Oceanic more mafic, (Gabbro/basaltic)
Asthenosphere vs. Lithosphere (difference in strength)
Lithosphere: - ANS part that is relatively rigid since it is not hot enough, rocks do not flow
2
Page
easily.. consists of crust and uppermost, coolest part of mantle
@COPYRIGHT @THEBRIGHT 2025/2026
QUESTIONS AND ANSWERS
What is Physical geology/dynamic earth? - ANS The study of the processes of the Earth and
the composition
Scientific method: - ANS Hypothesis: a message expressing an opinion based on incomplete
evidence
Theory: scientific ideas supported by abundant evidence. passed many tests -failed none
Law: Statements that completely describe a specific relationship or phenomenon
Earths Formation; - ANS Initially homogeneous: all same parts
Differentiation event: Heat from collision + heat when matter starts to squeeze + heat from
decay of radioactive elements results in denser iron alloy separating out and lighter material
rising
present state of differentiation:
lithosphere/lithospheric motions
Earth's Interior - ANS Crust: (Oceanic and Continental):
Oceanic Crust: 7-10km thick. Top is a thin layer of clay and tiny shells.. beneath consists of
basalt and below that, gabbro
1
Page
@COPYRIGHT @THEBRIGHT 2025/2026
, Continental Crust: - ANS 35-40km Thick. Rock type ranges from mafic to felsic. Continental
on average less mafic (felsic to intermediate composition) than oceanic, furthermore less
dense. Oxygen = most abundant
Mantle - ANS 2885 Km thick layer - largest part of earth. Consists entirely of ultramafic (dark
and dense) rock called peridotite, making peridotite most abundant rock on planet. Almost all
mantle is solid rock but its soft enough that it flows
Outer/Inner Core: - ANS Outer core: liquid iron alloy, this flow of iron alloy creates magnetic
field
Inner core: solid iron because of pressure
Gradients in Earth: - ANS Pressure and temperature both increase with depth in the Earth.
The rate at which temperature increases as depth increases is the geothermal gradient.
Sources of energy for the earth - ANS Interior: 80% of energy from decay of radioactive
elements
Exterior: Sun
Exterior Processes (Fast): - ANS Wind, weather, rivers, currents, glaciers
Interior (Slow): - ANS plate tectonics.. mountain building, earthquakes, landslides, volcanoes,
oceans open/close...
Continental vs. Oceanic crust (difference in thickness and composition) vs. Mantle
Continental 35-40km thick, oceanic 7-10km... Continental more felsic/intermediate, less dense..
Oceanic more mafic, (Gabbro/basaltic)
Asthenosphere vs. Lithosphere (difference in strength)
Lithosphere: - ANS part that is relatively rigid since it is not hot enough, rocks do not flow
2
Page
easily.. consists of crust and uppermost, coolest part of mantle
@COPYRIGHT @THEBRIGHT 2025/2026
