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Questions and Answers
What material is described as essentially impermeable in the experiment?
What material is described as essentially impermeable in the experiment?
Which material allowed the most water to pass through during the demonstration?
Which material allowed the most water to pass through during the demonstration?
What is the permeability of sand compared to gravel?
What is the permeability of sand compared to gravel?
Which of the following materials serves as a good groundwater reservoir under specific circumstances?
Which of the following materials serves as a good groundwater reservoir under specific circumstances?
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Why are materials like clay and unfractured rocks barriers to groundwater flow?
Why are materials like clay and unfractured rocks barriers to groundwater flow?
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What feature must be identified to quantify the availability of groundwater?
What feature must be identified to quantify the availability of groundwater?
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What happens to water on the land surface that infiltrates the ground?
What happens to water on the land surface that infiltrates the ground?
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What is the primary function of an aquifer?
What is the primary function of an aquifer?
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Which type of aquifer is directly connected to Earth's surface?
Which type of aquifer is directly connected to Earth's surface?
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What materials typically restrict the flow of groundwater?
What materials typically restrict the flow of groundwater?
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What characterizes confined aquifers?
What characterizes confined aquifers?
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What role do interconnected spaces within an aquifer play?
What role do interconnected spaces within an aquifer play?
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Which of the following best defines a confining unit?
Which of the following best defines a confining unit?
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What primarily supplies water to confined aquifers?
What primarily supplies water to confined aquifers?
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What can cause a decline in the depth of the water table?
What can cause a decline in the depth of the water table?
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What type of aquifers are predominantly found in southern states in the U.S.?
What type of aquifers are predominantly found in southern states in the U.S.?
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What type of plate motion generates earthquakes when plates move apart?
What type of plate motion generates earthquakes when plates move apart?
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What occurs when two tectonic plates collide, causing one to subduct beneath the other?
What occurs when two tectonic plates collide, causing one to subduct beneath the other?
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Which type of fault occurs as a result of tension in the crust?
Which type of fault occurs as a result of tension in the crust?
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What is the term for a fold that has an upward bend?
What is the term for a fold that has an upward bend?
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Which type of fault is characterized by rocks sliding past each other horizontally?
Which type of fault is characterized by rocks sliding past each other horizontally?
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What geological feature is formed by compressive forces causing layers to bend downwards?
What geological feature is formed by compressive forces causing layers to bend downwards?
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Study Notes
Groundwater and Structural Geology Module
- Groundwater accounts for about a quarter of the US freshwater supply, primarily used for domestic and agricultural purposes.
- Two key properties for understanding groundwater are porosity and permeability.
- Porosity is the proportion of void space in a material.
- Permeability is the ability of water to flow through a material.
- Groundwater is commonly stored in the spaces between grains of sand and gravel.
- Porosity was demonstrated using a beaker filled with gravel and water, showing approximately 40% of the volume was pore space. Similar experiments were conducted using sand, showing approximately 33% porosity.
- Permeability varies among different materials (e.g., gravel, sand, clay). Gravel has high permeability allowing water to flow quickly, clay has low permeability. Experiments showed different flow rates among materials when water was poured through funnels containing these materials.
- Different rock types can have varying porosity and permeability. Sandstone, which is compacted sand, has reduced porosity compared to loose sand, however, can still be a good aquifer. Limestone, which can dissolve to form large spaces, can also be an aquifer in some formations. Igneous and metamorphic rocks generally have low permeability due to lack of porosity.
Water Table
- The water table is the top of the saturated zone, marking the boundary between the soil with water-filled pore spaces and the unsaturated zone containing only partially filled pore spaces.
- Water table levels are influenced by groundwater consumption and precipitation, as seen in examples from different areas like eastern North Carolina and Western Kansas. Water levels decline with increased consumption.
- Water table can be measured using wells. Reflecting water levels in wells are used to determine water table depth.
- Groundwater is extracted using wells and their positions relative to the ground surface depend on the water table's specific elevation. Wells are usually drilled to ensure water table is reached to facilitate extraction.
Aquifers
- Aquifers are underground reservoirs of rock or sediment containing groundwater.
- Aquifers are categorized into unconfined (open) and confined (closed).
- Unconfined aquifers are directly connected to the water table above; confined aquifers are separated from the surface water by an impermeable layer.
- Different materials like sandstone, gravel, and limestone form aquifers with varying permeabilities. Sand and gravel aquifers are more common than limestone aquifers.
Plate Tectonics
- Plate tectonics describe the movement of Earth's lithospheric plates (crust and upper mantle). Three main types of plate motions:
- Divergent: Plates move apart, creating new crust (e.g., mid-ocean ridges).
- Convergent: Plates collide, leading to subduction or mountain building.
- Transform: Plates slide past each other (e.g., San Andrea's Fault).
- Evidence of these motions, including folds and faults, are found in different geologic formations.
- Normal faults and reverse faults are types of faults that occur due to tension and compression in rocks from plate motions.
- Transform faults occur due to lateral stress, and involve one plate sliding past another.
- Folds and rifts are also structural features associated with plate tectonic activity. These features provide evidence of past movements in rocks.
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Description
Explore the essential concepts of groundwater, including its significance in the US freshwater supply and the key properties of porosity and permeability. Understand how these characteristics influence the storage and movement of water through different geological materials. Engage with practical experiments that illustrate these principles.
