Distinctive associations of third-order, erosional landforms
indented into second-order structural forms such as plains and
plateaus. They are produced by aqueous dissolution, either acting
alone or in conjunction with (and as the trigger for) other erosion
processes. Karst is largely restricted to the most soluble rocks,
which are salt, gypsum and anhydrite, and limestone and dolostone.
See also Dolomite rock; Gypsum; Limestone.
The essence of the karst dynamic system is that meteoric water
(rain or snow) is routed underground, because the rocks are
soluble, rather than flowing off in surface river channels. It
follows that dissolutional caves develop in fracture systems,
resurging as springs at the margins of the soluble rocks or in the
lowest places. A consequence is that most karst topography is
“swallowing topography,” assemblages of landforms
created to deliver meteoric water down to the caves.
Karst landforms develop at small, intermediate, and large
scales. Karren is the general name given to small-scale
forms—varieties of dissolutional pits, grooves, and runnels.
Individuals are rarely greater than 10 m (30 ft) in length or
depth, but assemblages of them can cover hundreds of square
kilometers. On bare rock, karren display sharp edges; circular pits
or runnels extending downslope predominate. Beneath soil, edges are
rounded and forms more varied and intricate.
Sinkholes, also known as dolines or closed depressions, are the
diagnostic karst (and pseudokarst) landform. They range from
shallow, bowllike forms, through steep-sided funnels, to
vertical-walled cylinders. Asymmetry is common. Individual
sinkholes range from about 1 to 1000 m (3 to 3300 ft) in diameter
and are up to 300 m (1000 ft) deep. Many may become partly or
largely merged.
Dry valleys and gorges are carved by normal rivers, but
progressively lose their water underground (via sinkholes) as the
floors become entrenched into karst strata. Many gradations exist,
from valleys that dry up only during dry seasons (initial stage) to
those that are without any surface channel flow even in the
greatest flood periods (paleo-valleys). They are found in most
plateau and mountain karst terrains and are greatest where river
water can collect on insoluble rocks before penetrating the karst
(allogenic rivers).
Poljes, a Serbo-Croatian term for a field, is the generic name
adopted for the largest individual karst landform. This is a
topographically closed depression with a floor of alluvium masking
an underlying limestone floor beveled flat by planar corrosion.
Karst plains and towers are the end stage of karst topographic
development in some regions, produced by long-sustained dissolution
or by tectonic lowering. The plains are of alluvium, with residual
hills (unconsumed intersinkhole limestone) protruding through.
Where strata are massively bedded and the hills are vigorously
undercut by seasonal floods or allogenic rivers, they may be
steepened into vertical towers.
Earthcache requirements:
There are two "Welcome to Grassy Cove signs on the main drag.
Email me the distance of the bottom of the sink, using the distance
from the two welcome signs.
Email me the elevation on your GPS from the store.
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signs.
1.) Picture requirement:
My intentions are to have you post your picture with the signs in
the background or some recognizable feature from Grassy Cove. If
you refuse to post your face in the picture, then each log must
have a unique picture for each log. Tilting the picture with a
photo program will not be acceptable for unique. Group photos must
reference who's picture you are in otherwise. A unique picture must
be included with every log if you are not in the picture. .
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