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GEOL 200 Introductory Physical GeologyMidterm exam questions and answers
Athabasca University
,GEOL 200 Introductory Physical Geology Midterm exam questions and answers Athabasca University
Name the four subsystems that constitute the Earth system.
The four components that constitute the Earth system:
a. atmosphere: the gaseous envelope surrounding the Earth.
b. hydrosphere: the water on or close to the surface of the Earth.
c. biosphere: the organic components.
d. geosphere: the inorganic components that include rock and other materials.
Which of the four subsystems do we concentrate on most in physical geology?
In physical geology we concentrate on the geosphere. Nonetheless, we will also examine how the
other components (or spheres) interact with the geosphere to explain processes that occur on and
inside Earth
What advantages does geothermal energy have over fossil fuels as a source of electric power
generation? What environmental problems are associated with the exploitation of geothermal
energy?
As a source of electricity, geothermal energy offers some advantages over fossil fuels because it has
no emissions such as those associated with coal, oil, or natural gas. However, steam from the hot
water often contains hydrogen sulphide gas, which is toxic, and the hot water itself may contain metal
ions in solution such as lead and mercury, which are harmful to biological organisms. The extraction of
water for geothermal energy may also lead to ground subsidence, although pumping the cooled water
back into the ground may circumvent this. Finally, geothermal fluids are commonly highly corrosive.
What is the difference between travertine and sinter?
When hot water discharges from the ground, it often has minerals crystallizing from solution as it
exits. Under such circumstances, deposits of calcite form travertine, while precipitating silica forms
sinter. The type of precipitate is determined by the geology of the subsurface.
What are geodes?
Geodes are rock cavity infills with an exterior that comprises layers of non-crystalline (amorphous)
silica, and an interior that is often hollow and contains well-formed crystals projecting inwards.
Geodes form when crystal growth fills in the cavities.
How do sinkholes form?
Sinkholes are depressions on the landscape that form when roofs of subterranean cavities collapse.
Alternatively, sinkholes can form when downward percolating groundwater enlarges cracks in soluble
rocks such as limestone, rock salt (halite), or gypsum.
How do speleotherms form?
,Speleotherms are deposits of calcite that form from dripping water in subterranean cavities. They
essentially belong to two main categories: stalactites and stalagmites. Stalactites are protrusions that
hang from the roof of caves that form as calcite precipitates from dripping water. They are often
found aligned with cracks in the cave ceiling. Stalagmites, on the other hand, are conical projections
that form on the cave floor as water precipitates from dripping water. Thus, stalactites grow
downwards, while stalagmites grow upwards.
What is hard water?
Hard water describes water with a high content of dissolved ions, particularly calcium and
magnesium. The calcium usually comes from the weathering of calcium-bearing minerals such as
calcite and dolomite. Magnesium is produced by the weathering of minerals that contain magnesium,
such as dolomite and ferromagnesium minerals.
What is the distinction between weathering and erosion?
Weathering is the "in place" disintegration and decomposition of unstable material at the Earth's
surface; erosion is the loosening and removal of material.
Why is artificial recharge sometimes carried out? How is this done?
Extraction of groundwater without adequate recharge can result in a negative water balance; that is,
the water table drops in elevation. A drop in the water table can result in a number of other problems
such as ground subsidence and compaction. To circumvent such problems, artificial recharge can be
used to augment natural recharge processes. Water used for artificial recharge includes flood waters
and treated industrial or domestic waste waters, which are collected and stored in specially-designed
infiltration ponds for percolating into the ground. Alternatively, water can be pumped into the ground
as opposed to letting it infiltrate from surface ponds.
What is saltwater intrusion?
In coastal areas, freshwater usually occurs in the ground as a distinct zone floating above a more
dense saltwater zone. Saltwater intrusion refers to a process that occurs when wells sunk to tap
freshwater close to the coast are over-pumped such that the freshwater lens thins. Saltwater then
rises to fill the void left by the diminishing freshwater, and may eventually be discharged by the well if
pumping continues.
Why will a mineral that formed deep below the Earth's surface tend to break down at the Earth's
surface?
A mineral that formed deep below the Earth's surface is not at equilibrium at the low pressure and
temperature conditions at the Earth's surface. The mineral is unstable at the Earth's surface and will
have the tendency to break down to form other, more stable, minerals.
, The outer layer of the Earth is called the crust. Identify the two types of crust and discuss the
differences between them.
The two types of crust are oceanic crust and continental crust. Oceanic crust is denser and thinner
than continental crust.
List three surficial processes by which rock, originally elevated by the Earth's internal processes, wears
down. Can you think of any others?
Three surficial processes by which rock that was originally elevated by Earth internal processes wears
down are flowing streams, waves, and glaciers. Other processes include landslides and wind erosion
Identify two processes by which water returns to the atmosphere. What are the two mechanisms by
which water precipitated on land can return to the sea
The two processes by which water returns to the atmosphere are evaporation and transpiration. The
two mechanisms by which water precipitated on land can return to the sea are by surface runoff in
streams and by percolation of groundwater
Identify and discuss, briefly, the three major types of plate boundaries.
The three major types of plate boundaries are • divergent: the plates are separating. • convergent:
plates are moving together. • transform: plates are sliding past one another
Define each of the terms listed below.
a) Lithosphere
b) Asthenosphere
c) Atmosphere
d) Hydrosphere
a. lithosphere: the relatively rigid crust and the uppermost part of the mantle
b. asthenosphere: the part of the upper mantle that behaves plastically; the asthenosphere underlies
the solid lithosphere
c. atmosphere: the gaseous component of the Earth's surface fluids—air
d. hydrosphere: the water component of the Earth's surface fluids
What is the distinction between lithified and cemented?
A cemented rock has a material (cement) that has been added between the grains to bind them
together. A lithified rock is any rock in which the grains do not easily separate. A rock may be lithified
by cementation, compaction, or recrystallization.
a. What is the current estimate of the age of the Earth?
b. According to recent theory, when did the first dinosaur appear, and when did dinosaurs become
extinct?
c. According to recent theory, when did the first humans appear on Earth?
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