NGWA GENERAL DRILLING CERTIFICATION
PRACTICE EXAM Questions And Correct Answers
(Verified Answers) Plus Rationales 2026 Q&A |
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1. What is true about the origin of rocks?
A) Sandstones form from volcanic activity
B) Limestones come from deep mantle cooling
C) Sandstones were once sand deposits, limestones often contain fossils from shallow
seas, and shales were once clay beds
D) All rocks are igneous in origin
Correct Answer: C
Explanation: This describes the sedimentary rock cycle where deposits compact over time;
these are key indicators for identifying aquifers.
2. What are the three main types of rock?
A) Limestone, granite, marble
B) Igneous, sedimentary, metamorphic
C) Sandstone, shale, basalt
D) Volcanic, clastic, chemical
,Correct Answer: B
Explanation: The rock cycle classifies all rocks into these three categories based on
formation (cooling lava, lithification, heat & pressure).
3. Water would be least likely found in what geological formation?
A) Sandstone
B) Limestone
C) Granite
D) Gravel
Correct Answer: C
Explanation: Granite is an impermeable igneous rock with low porosity, making it an
aquiclude rather than an aquifer.
4. Ground water, like surface water, has a tendency to flow downhill.
A) True
B) False
Correct Answer: A
Explanation: Groundwater moves via gravity from high hydraulic head (pressure) to low
head, following the slope of the water table.
,5. More than 90% of our nation's fresh water is underground.
A) True
B) False
Correct Answer: A
Explanation: Excluding water locked in ice caps, groundwater represents the vast majority
of available liquid freshwater.
6. Artesian pressure is generally...
A) Caused by a pump
B) A result of gravity and confining beds
C) Due to geothermal heating
D) Created by tidal forces
Correct Answer: B
Explanation: Artesian conditions occur when water in a confined aquifer is under pressure,
causing the water level in a well to rise above the top of the aquifer.
7. What type of boundary creates a confined aquifer?
A) Water table on top only
B) Impermeable layer above and below the aquifer
C) Open boundary to the surface
D) Fractured granite only
Correct Answer: B
Explanation: A confined aquifer is sandwiched between low-permeability layers (confining
beds), trapping pressure.
, 8. Which geological formation is most likely to yield high volumes of water to a
well?
A) Shale
B) Granite
C) Sandstone
D) Clay
Correct Answer: C
Explanation: Sandstone possesses high porosity (storage space) and permeability
(connected pores) compared to shale or granite.
9. The water table is defined as...
A) The top of a confined aquifer
B) The upper surface of the zone of saturation
C) The bottom of the well
D) The level of the pump intake
Correct Answer: B
Explanation: The water table separates the unsaturated zone (vadose zone) from the
saturated zone below where pore spaces are filled with water.
10. Porosity is defined as...
A) The ability to transmit water
B) The volume of open space within a rock or sediment
PRACTICE EXAM Questions And Correct Answers
(Verified Answers) Plus Rationales 2026 Q&A |
Instant Download Pdf.
1. What is true about the origin of rocks?
A) Sandstones form from volcanic activity
B) Limestones come from deep mantle cooling
C) Sandstones were once sand deposits, limestones often contain fossils from shallow
seas, and shales were once clay beds
D) All rocks are igneous in origin
Correct Answer: C
Explanation: This describes the sedimentary rock cycle where deposits compact over time;
these are key indicators for identifying aquifers.
2. What are the three main types of rock?
A) Limestone, granite, marble
B) Igneous, sedimentary, metamorphic
C) Sandstone, shale, basalt
D) Volcanic, clastic, chemical
,Correct Answer: B
Explanation: The rock cycle classifies all rocks into these three categories based on
formation (cooling lava, lithification, heat & pressure).
3. Water would be least likely found in what geological formation?
A) Sandstone
B) Limestone
C) Granite
D) Gravel
Correct Answer: C
Explanation: Granite is an impermeable igneous rock with low porosity, making it an
aquiclude rather than an aquifer.
4. Ground water, like surface water, has a tendency to flow downhill.
A) True
B) False
Correct Answer: A
Explanation: Groundwater moves via gravity from high hydraulic head (pressure) to low
head, following the slope of the water table.
,5. More than 90% of our nation's fresh water is underground.
A) True
B) False
Correct Answer: A
Explanation: Excluding water locked in ice caps, groundwater represents the vast majority
of available liquid freshwater.
6. Artesian pressure is generally...
A) Caused by a pump
B) A result of gravity and confining beds
C) Due to geothermal heating
D) Created by tidal forces
Correct Answer: B
Explanation: Artesian conditions occur when water in a confined aquifer is under pressure,
causing the water level in a well to rise above the top of the aquifer.
7. What type of boundary creates a confined aquifer?
A) Water table on top only
B) Impermeable layer above and below the aquifer
C) Open boundary to the surface
D) Fractured granite only
Correct Answer: B
Explanation: A confined aquifer is sandwiched between low-permeability layers (confining
beds), trapping pressure.
, 8. Which geological formation is most likely to yield high volumes of water to a
well?
A) Shale
B) Granite
C) Sandstone
D) Clay
Correct Answer: C
Explanation: Sandstone possesses high porosity (storage space) and permeability
(connected pores) compared to shale or granite.
9. The water table is defined as...
A) The top of a confined aquifer
B) The upper surface of the zone of saturation
C) The bottom of the well
D) The level of the pump intake
Correct Answer: B
Explanation: The water table separates the unsaturated zone (vadose zone) from the
saturated zone below where pore spaces are filled with water.
10. Porosity is defined as...
A) The ability to transmit water
B) The volume of open space within a rock or sediment
