WHAT IS A SINKHOLE?

Sinkholes are a depression in land surface created by displacement of soil and/or ground water circulating and causing a solution of limestone. Sinkholes have always been a part of Florida life, but with the relatively recent population explosion, accompanied by rapid construction growth and the high amounts of water being pumped from Florida's water supply, the number of instances of property damage is escalating. L.R.E. Ground Services specializes in all types of sinkhole repairs. Illustrated below is a general depiction on how a collapse sinkhole may occur:

Sinkholes are a common feature of Florida's landscape. They are only one of many kinds of karst landforms. Karst landforms refer to the characteristic terrain produced by erosional processes associated with the chemical weathering and dissolution of limestone or dolomite, the two most common carbonate rocks in Florida.

Dissolution of carbonate rocks begins when they are exposed to acidic water. Most rainwater is slightly acidic and usually becomes more acidic as it moves through decaying plant debris. Limestones in Florida are porous, allowing the acidic water to percolate through their strata, dissolving some limestone and carrying it away in solution.

Over time, this persistent erosional process has created extensive underground voids and drainage systems in much of the carbonate rocks throughout the state. Collapse of overlying sediments into the underground cavities produces sinkholes, and the results can be devastating.

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LEGEND: RED - *Cover is more than 200 feet thick and consists of cohesive sediments interlayered with discontinuous carbonate beds. Sinkholes are very few, but several large diameter, deep sinkholes occur. Cover-collapse sinkholes dominate. Green - *Cover is 30 - 200 feet thick and consists mainly of cohesive clay sediments of low permeability. Sinkholes are most numerous of varying size and develop abruptly. Cover-collapse sinkholes dominate. Blue - *Cover is 30-200 feet thick and consists mainly of incohesive and permeable sand. Sinkholes are few, shallow, of small diameter and develop gradually. Cover- subsidence sinkholes dominate. Pink - Bare/ thinly covered limestone - Sinkholes are few, generally shallow and broad and develop gradually. Solution sinkholes dominate. *Cover is a general term used to describe sediments and sedimentary rock that lie above the limestone. Disclaimer: Research and geologic data derived and developed by the Florida Department of Environmental Protection (FDEP) - Florida Geological Survey (FGS) to carry out agency responsibilities related to management, protection, and development of Florida's natural resources. The development of these data sets represents a major investment of FDEP/FGS staff time and effort. Although efforts have been made to make the information accurate and useful, the FDEP/FGS and L.R.E. Ground Services, Inc. assumes no responsibility for errors in the information and does not guarantee that the data are free from errors or inaccuracies. Similarly FDEP/FGS and L.R.E. Ground Services, Inc. assume no responsibility for the consequences of inappropriate uses or interpretations of the data. As such, these digital data are distributed on an "as is" basis and the user assumes all risk as to their quality, the results obtained from their use, and the performance of the data. FDEP/FGS and L.R.E. Ground Services, Inc. bears no responsibility to inform users of any changes made to this data. Anyone using this data is advised that precision implied by the data may far exceed actual precision. For educational purposes only. http://www.dep.state.fl.us/geology/disclaimer.htm

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GLOSSARY OF TERMS

aquifer - a water-saturated zone of rock below the Earth's surface capable of producing water in useful quantities, as from a well.

confined aquifer - a zone of subsurface water-bearing rocks that contain water under pressure due to zones above and below it having low permeability, which restrict the flow of water into and out of it. An artesian aquifer is a type of confined aquifer.

dolomite - CaMg(CO3)2, a rock-forming, carbonate mineral, very common in Florida erosion - the natural processes of weathering, disintegration, dissolving, and removal and transportation of rock and earth material, mainly by water and wind, as well as by ice.

exotic terrain - a terrain that has undergone significant motion or travel with respect to the stable continent to which it is accreted. Florida could be considered an exotic terrain with respect to the North American continent, because it is thought to have once been part of northwestern Africa.

geomorphology - the branch of geology which deals with the form of the Earth, the configuration of its surface, and the changes that take place in land forms over time.

heavy minerals - a suite of accessory minerals of a sedimentary rock or sediments having specific gravities greater than 2.9. The most common heavy minerals found in Florida are: rutile, ilmenite, leucoxene, staurolite, zircon, kyanite, sillimanite, tourmaline, spinel, topaz, corundum, and monazite.

karst - a type of terrain characterized by sinkholes, caves, disappearing streams, springs, rolling topography, and underground drainage systems. Such terrain is created by ground-water dissolving limestone.

limestone - a bedded sedimentary deposit consisting chiefly of calcium carbonate. Limestone is an important and widely distributed of the carbonate rocks; it is the consolidated equivalent of limy mud, calcareous sand, or shell fragments.

percolation - movement of water through the pores or voids in rock or soil permeability - a measure of a porous material's ability to allow fluids or gases to flow through its pores. An important property of rocks that determines how much and how rapidly fluids or gases can move through them; for example, how much water can be pumped from an aquifer (see: porosity).

porosity - a measure of the amount of voids (pores) in a material. An important property of rocks that determines the quantities of fluids or gases they can store; for example, the amount of water an aquifer can store (see: permeability).

potentiometric surface - an imaginary surface defined by the level to which water in an aquifer would rise in a well due to the natural pressure in the rocks.

precipitation - 1. hydrology: water discharged from the atmosphere in the form of fog, rain, snow, sleet, or hail. 2. chemistry: the process of separating different minerals from a solution by evaporation; for example, salt from sea water.

sandstone - a type of sedimentary rock made of sand grains cemented together sinkhole - a depression in the land surface, usually round or funnel-shaped, that connects with a subterranean passage created by solution of limestone rocks by circulating ground water. Sinkholes may also form by collapse of a cavern roof.

solution feature - a topographic or geomorphic feature of a landscape that was formed as a result of water dissolving rocks, usually limestone or dolostone, such as: sinkholes, caves, disappearing streams, springs, and sinkhole lakes.

stratigraphy - the branch of geology that studies the formation, composition, sequence, and correlation of the layered rock-sequences that make up the Earth's crust.

structural geology - the branch of geology concerned with the deformation of rock bodies and with interpreting the natural forces that caused the deformations swale - a shallow depression in the land's surface which may be filled with water. In karst terrain it may indicate an incipient sinkhole forming.

transmissivity - a property of an aquifer which defines the rate at which water moves through it.

unconfined - in reference to aquifers, it describes a condition whereby water-bearing rocks are at atmospheric pressure, i.e., water table conditions.

vug - A cavity, void or large pore in a rock that is commonly lined with mineral precipitates

water table - in an aquifer, it is the upper surface of the zone of saturation under unconfined conditions; water in the rocks is at atmospheric pressure.

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