Ground Subsidence Flashcards
True or False: Surface or Ground Subsidence is both sporadic and incremental event
True; Sudden Collapse - sporadic; Slow Subsidence - incremental
Defined as the lowering of the land surface due to
sinkhole development
Surface Subsidence and Collapse
Subsidence due to _______ collapse in karst is
one of the most dangerous geohazards due to its
extreme unpredictability
Sinkhole
Water in the atmosphere can dissolve small amounts
of carbon dioxide (CO2
).
This results in rain water having a small amount of
___________ when it falls on the Earth’s
surface.
Carbonic acid (H2CO3)
Mining activities that remove material from below
the surface can result in collapse if precautions are
not taken to ensure that the there is adequate
support for the overlying rocks. Give 2 example of these mining actuvities
Salt mining and Coal Mining
This decreases if fluids are withdrawn from below the surface, resulting in the
removal of support and possible collapse
fluid pressure
What are the two most important fluids that occur beneath
the surface
water (in the form of groundwater),
and petroleum (in the form of oil and natural gas)
In the Wilmington oil field of Long
Beach, California, subsidence was first
recognized in 1940 due to withdrawal of
oil from the subsurface. The area
affected was about 50 km2. Near the
center of this area, the surface subsided
by up to ________.
9 meters
This subsidence event that has occurred in Wilmington oil field of Long
Beach, California costed over __________.
$100 Million
It means depression in the landscape.
Dolines
Other words for “Dolines”
Sinkhole, swallet, and swallow hole
What are the several processes that form dolines?
surface solution, cave collapse, piping, subsidence, and stream removal of superficial covers
What are the five-fold classification of dolines?
- Solution Dolines
- Collapse Dolines
- Suffossion Dolines
- Subsidence Dolines
- Alluvial stream-sink dolines
These dolines start where solution is concentrated around a favorable point such
as joint intersections. The solution lowers the bedrock surface, so eating out
a small depression.
The depression traps water, encouraging more solution and depression enlargement.
Solution Dolines
These dolines are produced suddenly when the roof of a cave formed by
underground solution gives way and fractures or ruptures rock and soil.
Collapse Dolines
These dolines form in an analogous manner to subjacent karst-collapse dolines, with a blanket of superficial deposits or thick soil being washed or falling into
widened joints and solution pipes in the limestone beneath.
Suffossion Dolines
These dolines form gradually by the sagging or settling of the ground
surface without any manifest breakage of soil or rock
Subsidence Dolines
These dolines form in alluvium where streams descend into underlying calcareous rocks. The stream-sink is the point at which a stream disappears underground.
Alluvial Stream-Sink Dolines
What is the diameter of the collapse dolines at the water table in Wood Buffalo National Park, Alberta, Canada. The dolines are created by collapses through dolostone into underlying gypsum.
40–100m
Types of Sinkholes based on Tihansky (1999):
Solution sinkholes
Subsidence sinkholes
Collapse sinkholes
Pipe sinkholes
It has small lake in closed depression in limestone, due to an impervious clay floor or to intersection of depression with the water table.
Solution sinkholes
It has lowering of the surface of the ground because of removal of support. Caused in karst
areas by subterranean solution or collapse of caves
Subsidence sinkholes
It is a closed depression formed by
the collapse of tie roof of a cave
Collapse sinkholes
It is a vertical cylindrical hole - attributable to solution, often without surface expression, filled with
debris, such as sand, clay, rock chips, and bones
Pipe Sinkholes
