Answers to the questions are required or your log will be deleted!
In order to receive credit for visiting this EarthCache, please complete the following tasks and email your answer to me within three days through my geocaching profile.
1. Measure the distance across the lime sink. Walk to the opposite side of the lime sink from the posted coordinates. Use your GPS receiver to mark a waypoint. What is the distance across the lime sink from the posted coordinates?
2. Determine the level of the water on the day of your visit. Using a yardstick or measuring tape, measure the distance from the top of the water level to the top of the bank. How far is the water below the bank?
3. Optional: Take a photo of yourself at the lime sink showing the level of the water and post to the cache page.
What is a lime sink?
Lime sinks, otherwise known as sinkholes, are found in limestone areas such as Florida and Georgia. Water trickles through the limestone ground over a period of thousands of years, creating caves underneath which eventually collapse, forming deep holes. These can be dry holes but sometimes hold standing water, creating a type of wetland. A sinkhole is a naturally occurring geological phenomenon that causes a large depression to form in the ground, often hundreds of feet wide and dozens of feet deep. Prevalent in areas where layers of water soluble subterranean rock are covered with soil, sinkholes can open unexpectedly, sometimes creating a serious risk to both persons and property.
Why do sinkholes form?
Sinkholes form in karst terrain normally from the collapse of surface sediments into underground voids and cavities in the limestone bedrock. Slightly acidic ground water slowly dissolves cavities and caves in the limestone over a period of many years. When the cavity enlarges to the point that its ceiling can no longer support the weight of overlying sediments, the earth collapses into the cavity. Karst terrain is a type of topography that is formed by dissolution of bedrock in areas underlain by limestone, dolostone or, as in some western states, gypsum. Such terrain has underground drainage systems that are reflected on the surface as sinkholes, springs, disappearing streams or even caves.
Lime Sinks in Alabama, Florida, and Georgia
Lime sinks, springs and caves are to be found in many areas of Alabama, Florida, and Georgia. They appear in the area of the Interior Plateau, which stretches from the southern part of Indiana and Ohio to the northern part of Alabama. A number of sinkholes in the Dougherty Plain exist, many of which are filled with water and form oases for animals and plants. Sinkholes form as limestone gradually dissolves and collapses. This is accelerated by construction, such as building structures and drilling. Droughts and pumping both reduce groundwater. Both scenarios alter pressure in the water table, making limestone less stable.
A look at the factors and stages of sinkhole formation:
Causes
A typical sink hole forms when acidic ground water filtering down through overbearing layers of soil dissolve an underlying layer of soluble rock, such as limestone or gypsum. This leads to the formation of a void or space in rock, which eventually collapses, forming a depression in the surface.
Types
Three major types of sinkholes exist. The solution sinkhole typically forms in a joint, fracture or other line of weakness in limestone rock at the water table where limestone is either exposed or close to the surface. As the limestone dissolves, soil and other residue are gradually swept by wind, rain and gravity into the depression, often forming a gradual dip in the soil. In cover collapse sinkholes the ceiling of a void may thin to the point where it can no longer support the weight of the overbearing soil and rock. Eventually the ceiling collapses suddenly, producing a large hole. Cover subsidence sinkholes are caused by deep rock dissolving from under soil and allowing the soil to slump downward.
Influences
Several external influences can cause a sink hole to occur. When a cave is filled with water, the pressure the water exerts may help support the ceiling. If the water table drops due to drought or to pumping of excess water from the aquifer, the levels of water in the cave may drop, resulting in a collapse. Vibration from new construction or roads, increased pressure from rising water levels above the cave in ponds and lakes due to rain, broken water mains or a shift in the direction of flow of underground streams within the aquifer can also trigger a sinkhole.
Sources: saveoursuwanee.org, eHow.com