Karsts (Geomorphology)

Question 1

What is a Karst

Answer 1

A term that is applied to the topography of a region which is underlain by limestone, dolomite, gypsum, and other rocks which can be affected by dissolution

Question 2

What characterizes karst topography?

Answer 2

Surface depressions in which water is intercepted and diverted into underground caverns and passageways.

Question 3

What are the 4 conditions that are necessary for development of karst terrain?

Answer 3

1. A soluble rock, preferably limestone, at or near the surface.
2. A dense rock, highly jointed and thin-bedded
3. Entrenched valleys below uplands underlain by soluble and well jointed rocks
4. A region of moderate to abundant rainfall

Question 4

In what four areas are karsts and pseudokarst typically found?

Answer 4

Florida, southern Mississippi, a southerly trending belt from south central Indiana to Tennessee, and the Appalachian’s from Alabama to Pennsylvania

Question 5

What percent of the US land surface is karst?

Answer 5

20%

Question 6

What percent of groundwater used for drinking comes from karst aquifers?

Answer 6

40%

Question 7

What are sinkholes?

Answer 7

Circular depressions that are commonly funnel shaped and can be a few feet to a few hundred feet in diameter. They are the most common features of karst.

Question 8

What are the three kinds of sinkholes?

Answer 8

1. Solution sinkholes- occur when rainwater comes into contact with carbonate bedrock either directly or through a thin covering of soil. The water moves through joints and fractures, and the resulting land is gently undulating with shallow depressions and mounds.
2. Cover subsidence sinkholes- form structures here sand overlies the carbonate bedrock. As water moves through the sand and into bedrock fractures, it deposits some sand.
3. Cover collapse sinkhole- develop where there is a thick layer of clay above the soluble bedrock. The water moves through the clay and dissolves the bedrock below. They ultimately collapse and are often steep sided chimney like structures.

Question 9

Sinkholes are the most common karst features. What are other depositional features?

Answer 9

1. Dripstone- the travertines deposits that result from the calcium carbonate rich mineral are dripping from the ceiling forming stalagmites and stalactites.
2. Helictite- An irregular twig like deposit that forms in a cavern where there’s not enough water to form drips, but where the surface remains, damp, allowing carbonate to grow in any direction.
3. Travertine - a deposit of calcium carbonate precipitate that can be found in limestone caverns, coating the cavern walls, floors and ceilings.

Question 10

Blind Valley

Answer 10

A valley that ends at a swallow hole due to a prolonged period of upstream, erosion above the sink hole

Question 11

Cavern

Answer 11

Large caves that may extend in any direction, have one or several levels, and are created by solution of limestone along joints and bedding planes 

Question 12

Hum

Answer 12

Isolated hill remnants due to erosion by solution incarcerating 

Question 13

Karst window

Answer 13

A hole in the ground, in which one can observe an underground stream, flowing from one cavern to another. A hole in a cavern which breaks the surface. 

Question 14

Lapies

Answer 14

Grooved or fluted surfaces, resulting from the solution of limestone at or near the surface in an area of high relief. The grooves range and width from a few millimeters to more than a meter and width.

Question 15

Natural tunnels and bridges

Answer 15

Features produced by the underground flow of water in karst terrain. When the tunnel sections collapse leaving only small segments, bridges are formed.

Question 16

Polje

Answer 16

An elongated basin with a flat floor and steep walls formed by solution of a previously faulted or or folded structure. This feature can be 30 miles or more.

Question 17

Sink

Answer 17

The point at which a sinking creek ends, often in an observable swallow hole.

Question 18

Sinkhole or karst plain

Answer 18

A limestone plain exhibiting sieve like characteristics resulting from numerous sinkholes, intercepting any surface waters and diverting them to sub surface channels

Question 19

Sinkhole ponds or karst lakes

Answer 19

A pond or lake resulting from the clogging by clay of a doline sinkhole that perches water above the water table

Question 20

Sinking creeks

Answer 20

Any surface creek or stream which disappears underground in karst terrain; many disappear in a swallow hole

Question 21

Solution valley or karst valley

Answer 21

A transitional feature between surface and subsurface drainage in an area of clastic rocks. Special type of blind valley.

Question 22

Swallow hole

Answer 22

A hole in the bottom of a sinkhole which allows surface water, runoff or streams to flow into the sub surface cavities 

Question 23

Terra Rossa

Answer 23

A red clayey soil found, mantling the ground surface and extending into joints or fractures, resulting from surface or near surface solution, usually found on moderate to gentle slopes

Question 24

Uvala

Answer 24

An elongated karst window that has occurred by the collapse of an extensive portion of a subsurface waterway. These features can extend from 1000 feet to a mile or more.