Karst

What is required to develop a karstic cave system?

1. Lithology: Strong and pure rock: remain as rook of passageway. No buildup of insoluble material 2. Rock structure: ways by which groundwater can penetrate rock 3. Supply of water and sufficient topographic relief to generate a hydraulic gradient - determines the overall orientation of a cave

2 Classifications of karst Landforms

1. Surface features 2. Substrate features

2 Factors that determine the amount of CO2 in solution

1. Temperature 2. Partial pressure

How much of the Earth's mass does karst landscape cover?

12-15%

About ____% of the global population is supplied largely or entirely by karst water

25%

Cenote

A circular water filled shaft in subdued karstic plains; developed through cave collapse or upward solution along fractures

Karren

A term used to describe all superficial small features typically found on limestone pavement Are typically small solution pits, grooves, and runnels

What do Speolothems indicate?

Amount of growth is an indicator of how much ground water percolates into the cave Little growth: drought Rapid growth: heavy precipitation

Speolothems

Cave depositions of precipitation of cave calcite and other materials

Collapse Sinkholes

Collapse of bedrock into an underlying solution cavity. Form when the top of the sinkhole collapses because drop in groundwater levels

Groundwater

Comes from precipitation. Water filters down through the vadose zone to reach the phreatic zone. The rate of infiltration is partially a function of soil and rock type and time

Helicites

Demonstrate the power of capillary action

Phreatic Caves

Develop completely in the pheratic zone Evidence: in the passageways - equal erosion of ceilings, walls, and floors

Staligmite

Develop where drops fall to the floor

Poljes

Elongated basins with flat floors and steep rock walls; floors are often covered by alluvium Flood during wet periods These are the largest karstic depressions

Pavement

Extensive horizontal bare rock surface

Exsurgent Spring

Fed mainly by the diffuse flow of water seeping down through the rocks

Intermediate Zone

Flow-gravitational or under pressure

Cockpit Karst

Form in wetter regions Sinkholes may coalesce Upside down egg carton

Gorges

Form when large volume streams flow over rocks susceptible to chemical weathering but not mass wasting. Result is deep valleys with very steep sides well past the angle of repose

Stalactite

Formed by drips on ceilings, from water percolating through joints or other fractures

Suffosion

How sinkholes form Occur when unconsolidated overburden sediments infill preexisting cavities below them

Caves - frequently associated with faulting

Hydraulic gradient creates the overall orientation but individual cave segments typically follow bedding planes, joints or faults

Where do caves develop?

In the unsaturated vadose Zone

Pressure Grouting

Injection of a low slump grout, which mainly consist of cement, sand, fly ash, into soils at/below limestone layer

Tower Karst

Isolated carbonate hills surrounded by flat plains Produced by over steepening of soluble rocks If there is alluvium or other permeable rocks in the tower there are often springs at the base of the tower

Mammoth Caves

Large cave developing at contact between limestone and impermeable rock (fairly thin and essentially flat laying rock)

Features of a Sinkhole

Limestone, carbonate rock Oval or circular shaped with sloping vertical sides Occur as an isolated entity or in groups

Allocthonous Sediments

Materials brought into the cave - mud, sand, gravel

Autochtonous Sediments

Materials created in the cave - calcareous products of solution and redeposition of material

Keyhole Passage

Modification by flow in the vadose as water level drops, the more circular portion formed by water flow in the pheratic zone

Vadose Caves

Mostly develop above the water table. Drainage is free flowing under gravity; cave passages have air above any water surface Exist in the upper part of karst aquifer Eventually drainage goes into pheratic zone or out to the surface

Calcite Straws

Precipitation of circular rings of calcite

Flowstone

Produced by water running or flowing down the walls and over the floors of caves (also known as cave bacon)

Karst Springs

Receive drainage from all sinkholes and sinking streams within its groundwater basin. Conduits carrying water from each point where water sinks join together underground, forming successively larger passages with ever-increasing flow, which eventually discharges at a spring. LARGE DISCHARGE

Disappearing Streams; Sinks

Rivers can disappear and reappear in karst terrain Places where the stream disappear are called sinks or vents

Signs that you may be living with Karst

Slumping or sagging - tilting of vertical objects Structural failure: cracks in mortar/pavement, windows/trim developing spaces, floors become uneven Rainfall pooling Vegetative stress - lowering of the water table Exposure of tree roots and rocks

Solution sinkholes

Solution acting from the surface downwards on fracture or joints. Form when the bedrock continues to be dissolved

Caves - frequently associated with jointing

Tend to be high, narrow and winding

Solution

The process by which karst forms in carbonate rocks (limestone)

Dissociation

The process by which karst forms in evaporites. It is the separation of cations and anions and their dispersal in water

Vadose Shaft

Water flowing down vertical or steeply dipping fractures

Hazards involved with living near karst

Water resource contamination due to the fact that karst is porous Can damage property

Vadose Zone

Zone of aeration that is unsaturated. It varies in thickness; function of sediment. The hydrostatic pressure is less than the atmospheric pressure. Gravity is pulling the water downward

Phreatic Zone

Zone of saturation. The hydrostatic pressure is greater than the atmospheric pressure; water flows easily

Resurgent Spring

fed by conduit flow where surface rivers disappear underground; react to rainfall faster with much greater maximum flows

Downward Sinkholes

lowering of the water table, removes buoyant supports and increase weight of roof

Polygonal Karst

star-shapped depression separated by residual cone-shaped or pinnacle shapped divides Common in Jamaica.... May form as the result of higher rainfall intensity in tropical regions which cause rapid runoff, surface flow, runnel and gully development