Geomorphology Flashcards
Define Karst
A term that is applied to the topography of a region which is underlain by limestone, dolomite, gypsum, or other rocks which can be affected by dissolution.
What are 4 conditions necessary for the development of karst terrain?
- a soluble rock (limesstone) at or near the surface
- A dense rock, highly jointed and thin-bedded.
- Entrenched valleys below uplands underlain by soluble rock and well-jointed rocks
- A region of moderate to abundant rainfall
Sinkholes: What? Environment?
Circular depressions that are commonly funnel-shaped and can be a few feet to a hundred feet in diameter. They are the most commonly observed karst feature.
Solution sinkholes
Occur when rainwater comes into contact with carbonate bedrock either directly or though a thin covering of soil.
Cover-subsidence sinkholes
Form where sand overlies the carbonate bedrock.
Cover-collapse sinkholes
Develop where there is a thick layer of clay above the soluble bedrock.
Dripstone
A depositional karst feature of travertine deposits that result from the CaCO3-rich water dripping from the ceiling of a cave or cavern.
Helictite
A depositional karst feature of an irregular twig like deposit that forms in a cavern where there is not enough water to form drips, but where the surface remains damp allowing the CaCO3 to grow in any direction
Travertine
A depositional karst feature of a deposit of CaCO3 precipitate that can be found in limestone caverns coating the cavern walls, floors, and ceilings.
Blind Valley
An erosional karst feature. It is a valley that ends at a swallow hole due to a prolonged period of upstream erosion above the sinkhole.
Cavern
Large caves that may extend in any direction, have one or several levels, and are created by the solution of limestone along joints and bedding planes.
Hum
Isolated hill remnants due to erosion by solution in karst terrain.
Karst Window
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.
Lapies
Grooved or fluted surface resulting from the solution of limestone at or near the surface in an area of high relief. Grooves commonly result in knifelike ridges.
Natural tunnels & bridges
Features produced by the underground flow of water in karst terrain. Bridges are formed when the tunnel sections collapse.
Polje
An elongated basin with a flat floor and steep walls formed by solution of a previously faulted or folded structure.
Sink
The point at which a sinking creek ends, often in an observable swallow hole.
Sinkhole or Karst plain
A limestone plain exhibiting sieve-like characteristics resulting from numerous sinkholes intercepting any surface waters and diverting them to subsurface channels.
Sinkhole ponds or karst lakes
A pond or lake resulting from the clogging of a (doline) sinkhole by clay that perches water above the water table.
Sinking creeks
Any surface creek or stream which disappears underground in karst terrain. Many disappear in a swallow hole.
Solution valley or karst valley
A transitional feature between surface and subsurface drainage in an area of clastic rocks. It is a special type of a blind valley.
Solution-subsidence trough
A non-tectonic feature, up to 10 miles long, resulting from concurrent subsidence and solution along joints or faults.
Swallow Hole
A hole in the bottom of a sinkhole which allows surface water runoff or streams to flow into the subsurface cavities.
Terra rossa
A red clayey (CL-CH) soil found mantling the ground surface and extending into joints or fractures resulting from surface or near surface solution. It is usually found on moderate to gentle slopes.
Uvala
An elongated karst window that has occurred by the collapse of an extensive portion of a subsurface waterway. These features can extend from 1000 ft to a mile or more.
What did continental glaciation cover during the last Ice Age?
Central and northern U.S.
Where is Alpine glaciation found?
Mountainous areas of Alaska, in the higher elevation of the Rockies, the Sierras, and the Cascades.
Drift
It is all rock and associated material that has been carried by and deposited by a glacier, glacial ice, or water running from a glacier.
Drumlin
An elongated ellipsoidal feature which can be composed of a wide variety of material ranging from till to relatively large rock fragments. The streamlined hills are usually clustered and found near the terminal or recessional moraines.
Esker
Serpentine shaped stratified deposits that develop as the load carried by the stream flowing beneath, within, and above the glacier, once the glacier becomes stained and is dropped.
Kame & Kame terrace
A small hummock or terrace of ice-contact drift that has resulted from the deposition of sediment either in crevasses at the surface of the glacier, or on the irregular surface of stagnant glaciers, or from streams flowing at the edge of the glacier along the contact of the ice with the valley wall. Sediments are usually stratified and contain poorly sorted sands (SW) and gravels (GW).
Kettle
A depression in the postglacial terrain formed by the melting of a large stagnant ice bock which allows for the settlement of the overlying glacial drift.
Arcuate terminal moraine
An arcuate moraine that has been deposited at the terminus of the glacier. marking the furthest progression of the glaciation.
Ground moraine
Can be composed of both the material contained within the glacier and the material being moved at the base of the glacier.
End moraine or Terminal moraine
Found at the maximum extent of a continental glaciation.
Recessional moraine
Moraines that have formed during a temporary hiatus in the retreat of the ice sheet.
Outwash plain
A broad plain composed of outwash: stratified depbirs that is carried by meltwater streams both in front of and beyond the terminal or end moraine.
The outwash plain is typically comprised of coarser grained materials (SW, GW) closer to teh terminus of the glacier grading to finer materials with increased distance.
Swell & Swale topography
Till deposits rich in clay that may result in a gently undulating surface whihc often is also found in areas that have had multiple glaciations
Till
An unsorted, unstratified glacial deposit composed of a herterogenous mixture of clay (CL), silt (ML), sand (SW), gravel (GW), and boulders.
It is usually unconsolidated and deposited directly by a glacier
Lacustrine Plains
A plain that has formed by the filling of a lake with lake sediments and alluvium which has been deposited along the margin of the glacier.
Characterized by very flat alley bottoms in hilly terrains.