EESA06H3 Chapter Notes - Chapter 15: Igneous Rock, Hydraulic Head, Schist

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12 Aug 2016
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Review & testing your knowledge (page 425-6)
1. What conditions are necessary for an artesian well?
- An artesian well occurs in a confined (pressurized) aquifer, where the level of the water in
the well rises above the top of the aquifer.
- When water under pressure rises in wells to a level above the top of the aquifer
- Sometimes spouts continuously into air unless it is capped
- Example: Dakota Sandstone aquifer
- Tilted and exposed to the surface due to erosion
2. What distinguishes a geyser from a hot spring? Why does a geyser erupt?
- A hot spring is a spring where water is warmer than human body temperature, while a
geyser is a type of near-boiling hot spring that periodically erupts hot water and steam
- Geysers erupt because of constriction in the underground “plumbing” of a geyser, which
prevents the water from rising and cooling
3. What is karst topography? How does it form?
- Karst topography consists of an irregular series of valleys, caves, and sinkholes created by
the solution of the underlying limestone bedrock by groundwater.
- Area with many sinkholes and with cave systems beneath the land surface
- Karst areas have lack of surface streams, although one major river may flow at a level lower
than the karst area
4. What chemical conditions are necessary for caves to develop in limestone? For stalactites to
develop in a cave?
- Develop when slightly acidic groundwater dissolves limestone along joints and bedding
panes, opening up cavern systems as calcite is carried away in solution
5. What causes a perched water table?
- A perched water table is caused by a low-permeability geologic material of limited extent
within the unsaturated zone that allows a localized mass of groundwater to accumulate
above.
- Top of a body of groundwater separated from main water table beneath it by unsaturated
zone
- Caused when groundwater collects above a lens of less permeable shale within a more
permeable rock like sandstone
- If perched water table intersects the land surface, a line of springs can form along the upper
contact of the shale lens
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