Clays play a role in land subsidence by ____.
a. weighing down organic material and compacting it, causing subsidence
b. swelling and causing runoff and subsidence in adjacent areas
c. absorbing moisture to counteract subsidence
d. blocking the absorption of groundwater by the aquifer, making subsidence likely downstream
e. collapsing into compact layers when dried, increasing subsidence
Question 2The decomposition of peat layers in soils ____.
a. releases sodium bicarbonate into groundwater
b. can result in flooding in land drained for farming
c. is usually caused when the peat layer is exposed by digging or tilling
d. happens during abnormally dry seasons
e. transforms the peat into clay
Question 3Land subsidence that results from petroleum mining ____.
a. is a necessary cost of fossil fuel production
b. can be mitigated by pumping fluid into the well
c. is a problem in the Middle East, but not in the United States
d. will be avoided if the well hole is sealed and capped after use
e. follows a different process than subsidence from groundwater mining
Question 4Land subsidence increases the hazard of ____.
a. earthquakes
b. hurricanes
c. landslides
d. drought
e. flooding
Question 5The effects of land subsidence due to groundwater extraction are generally ____.
a. problems for a period of months, until more groundwater seeps in to deep clays
b. permanent and irreversible
c. in effect for several years, until major storms irrigate the area
d. reversible by returning water to the aquifer
e. unpredictable and impossible to plan for effectively
Question 6The uneven, potholed surface of karst is caused by ____.
a. erosion from ancient streambeds
b. the pattern of deposited material from glaciers
c. hardening of volcanic ash into tuff
d. swelling due to the absorption of water
e. the dissolution of the surface in the presence of acids
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