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Descriptive Statements:
- Demonstrate knowledge of relative dating and the use of technology in absolute dating to develop the geologic time scale.
- Recognize causes and consequences of major events in Earth's geologic history.
- Demonstrate knowledge of Earth's origin and the development of the atmosphere and hydrosphere.
- Demonstrate knowledge of the origin and history of life, the fossil record, the process of fossil formation, and the theory of evolution.
Sample Item:
Which of the following statements describes the scientific basis of radiometric dating?
- The radioactivity of a rock sample is inversely related to the amount of time
that has passed since the rock was exposed at Earth's surface.
- The proportion of alpha particles to beta particles given off by radioactive
elements in a particular rock is a measure of the rock's age.
- The concentration of different types of radioactive isotopes in a rock indicates
the geologic period in which the rock formed.
- The proportion of radioactive parent atoms to daughter atoms in a rock is used
to calculate the time that has elapsed since the rock formed.
Correct Response and Explanation (Show Correct ResponseHide Correct Response)
D. This question requires the examinee to demonstrate knowledge of the
absolute dating of geologic events using the breakdown of naturally occurring radioactive
isotopes. This technique, known as radiometric dating, relies on the fact that different
radioactive isotopes have different decay rates that are constant under conditions found
in Earth's outer layers. As a radioactive isotope decays, it produces decay products,
known as daughter products, at a rate specific to that isotope. The proportion of the
original radioactive isotope in a rock to the daughter products that have formed over
time provides a tool for measuring the time that has elapsed since the rock first formed.
Descriptive Statements:
- Analyze the landforms and geologic features that result from tectonic processes, and the evidence and methods used to establish the theory of plate tectonics.
- Demonstrate knowledge of the causes, characteristics, and impacts of different types of volcanic activity and the nature of erupted materials.
- Demonstrate knowledge of the causes, characteristics, and impacts of the geologic faulting and folding associated with earthquakes and mountain building.
- Analyze the physical and chemical processes involved in the formation of metamorphic, igneous, and sedimentary rocks within the rock cycle.
Sample Item:
The upwelling of magma in an active volcano has the greatest potential for producing a
dangerous pyroclastic flow if the magma:
- contains a high concentration of dissolved gases and a high silica content.
- is basaltic and contains very little water vapor.
- contains low levels of volatile gases and erupts at a relatively high temperature.
- is andesitic and has a relatively low viscosity.
Correct Response and Explanation (Show Correct ResponseHide Correct Response)
A. This question requires the examinee to demonstrate knowledge of the
characteristics of different types of volcanic activity. Pyroclastic flows are associated
with explosive eruptions from composite cones. Typically, the magma has a high silica
content, making the magma relatively viscous, and a high concentration of dissolved gases.
As the magma moves upward, the gases in it are unable to escape from the magma because of
its high viscosity. Pressure builds within the volcano toward a sudden explosive eruption.
Pyroclastic flows can be triggered by a lateral explosion from a composite volcano or, more
commonly, from the collapse of a tall eruption column emitted during a major explosion from
the top of the volcano's main vent. Pyroclastic flows consist of a mix of heated gases,
incandescent ash, and rock fragments that move rapidly down the slopes of a volcano, often
at speeds over 100 miles per hour.
Descriptive Statements:
- Demonstrate knowledge of the origin, characteristics, and classification of minerals, soil types, and rocks.
- Analyze the formation, extraction, and use of geologic resources.
- Demonstrate knowledge of Earth's interior and the evidence and methods used to study Earth's internal structure.
Sample Item:
Which of the following physical properties is used to classify minerals in Bowen's
reaction series?
- crystallization temperature
- specific gravity
- crystal form
- hardness
Correct Response and Explanation (Show Correct ResponseHide Correct Response)
A. This question requires the examinee to demonstrate knowledge of the
classification of minerals. Bowen's reaction series is a mineral classification scheme
that describes the sequence in which minerals crystallize from a magma as the magma cools.
For example, minerals containing iron, magnesium, and calcium crystallize first from the
hot magma, depleting the remaining magma of these elements. As the magma cools, the very
last minerals to form from the depleted magma are potassium feldspar, muscovite mica, and
quartz.
Descriptive Statements:
- Analyze the processes and effects of physical and chemical weathering.
- Analyze erosional processes and the impacts of erosion.
- Demonstrate knowledge of the physical properties of alpine and continental glaciers and the ways in which they alter the landscape.
- Demonstrate knowledge of the processes of sediment transport and deposition in aquatic and terrestrial environments.
- Demonstrate knowledge of how climatic and geographic conditions affect the landscape.
Sample Item:
The formation of karst topography in regions underlain by limestone occurs when:
- calcium carbonate combines with water molecules to form a hydrated compound that
is easily dissolved.
- alkaline groundwater saturates and erodes cracks within the bedrock due to a rise
in the elevation of the water table.
- carbonic acid in groundwater reacts with calcite, forming calcium bicarbonate, a
soluble mineral.
- tectonic uplift exposes marine sediments to physical weathering that breaks up
carbonate rocks along bedding planes.
Correct Response and Explanation (Show Correct ResponseHide Correct Response)
C. This question requires the examinee to analyze the process that
produces karst topography in regions underlain by limestone deposits. The development
of karst topography begins with the chemical weathering of limestone as it reacts with
groundwater. The groundwater is slightly acidic because it contains carbonic acid. The
carbonic acid in groundwater is produced by the interaction of precipitation with carbon
dioxide in the atmosphere and in soils. The carbonic acid in groundwater reacts with
calcium carbonate (calcite), the primary component of limestone, to produce calcium
bicarbonate. Since the calcium bicarbonate is a mineral that is soluble in water, it
is carried away in the groundwater. Over geologic time, this chemical weathering process
produces the caverns, sinkholes, and caves associated with karst topography.
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