Sinkhole

As water slowly dissolves the limestone roof of a cave, the roof becomes weak and may eventually collapse. The result Is a sinkhole. When a source of water remains, the sinkhole fills to form a lake that can be very scenic. 

At the medium reach, the river flows into the Iberian Depression, with marl and gypsum Miocene deposits in some areas. The dissolution of evaporitic sediments (gypsum, halite, and sodium-sulfates) gives rise to numerous sinkholes. However, subsidence is also being masked by morpho-sedimentary dynamic processes such as aggradation and erosion [12]. 

Once on the ground, the water moves through the soil and picks up more carbon dioxide from decaying plants and animals, forming more carbonic acid. As carbonic acid passes through the soil and reaches the rock below, it can seep into the cracks and pores of rocks. When carbonic acid encounters one type of rock—limestone—the acid dissolves the rock. In areas where much of the underlying rock is limestone, certain landforms such as caves, sinkholes, and potholes, are common. 

When the ceiling of a cave collapses, it forms a sinkhole. In the United States, sinkholes are most often found in Florida, Texas, Alabama, Missouri, Kentucky, Tennessee, and Pennsylvania. That is because these states have a lot of limestone rock. 

Perlman, Howard. Sinkholes. Water Science for Schools. U.S. Geological Survey. Available online. URL http //ga.water.usgs. gov/edu/earthgwsinkholes.html. Accessed Dec. 17, 2006. 

Karst An area underlain with thick limestones or other carbonate rocks, which results in abundant sinkholes and caves. 

Fig. 2.8 Components of a karstic system sinkholes and fissures acting as inlets for rapid intake of runoff water dissolution channels water discharging in springs at local bases of drainage, for example, river beds caves exposed at former dissolution channels formed at former (higher) drainage bases.

A conduit type of rapid karstic flow, recognized by adjacent sinkholes and by the muddy, or turbid, water... 

Feedlots are sited close to existing water supply wells and rivers used for water supply (these pose a greater threat than facilities located at a distance from water supplies). Feedlots are located next to sinkholes, abandoned mine shafts, abandoned wells or other features that allow drainage direct access to the water table. 

Keep the spill out of any body of water or any pathway that will lead to water, such as a ditch, floor drain, well, or sinkhole. If the spilled pesticide is flowing towards such an area, block it or redirect it. 

Locate pesticide storage facilities at least 100 feet from wells, springs, sinkholes, and other sites that directly link to groundwater to prevent their contamination from runoff or firefighting water. 

Sinkholes are especially troublesome. Surface water often flows into sinkholes and disappears quickly into the groundwater. If a pesticide is released into an area that drains into a sinkhole, even a moderate rain or irrigation may carry some of the pesticide directly to the groundwater. 

Karst aquifers receive inputs of sediment from sinking streams and from storm runoff into sinkholes. Runoff from overlying caprock may flush sediment down vertical shafts and so carry fragments of the caprock material deep into the carbonate aquifer. In addition, diffuse infiltration through overlying soils and the epikarst may transmit soils... 

Logsdon River has been explored upstream from the confluence for more than seven kilometers. It more or less parallels the escarpment at the southern edge of the Mammoth Cave Plateau and is a master drain for the karst as far northeast as Roppel Cave. It is known to receive recharge from valley drains and vertical shafts and also from the sinking streams and sinkhole inputs on the Sinkhole Plain to the southeast. The Logsdon River sediments are mainly silts and fine sands with 40 - 60% of the material smaller than the smallest sieve size used. 

The contrast between the two tributaries could be a matter of provenance, a contrast between sediment derived from the Plateau compared to sediment derived from the Sinkhole Plain, it would also be a matter of transport with Hawkins River being the higher energy stream. 

Sediments were also subsampled from each of the four stratigraphic layers of the sequence. In order to examine the relationship of cave sediments to modern, nearby depositional settings, samples were also collected from a nearby sinkhole pond with hand operated coring device and from the high terrace and flood plain soils with a shovel (Fig. 1). 

The fourth general stage of development in the caves of Lime Creek was abandonment. Downcutting and piracy of cave streams to lower routes left some of the lower caves near Lime Creek Canyon without significant flow. Presently, these caves take water captured as snow and rain in sinkhole entrances and through open fractures. 

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