Crystal Cave - Cave Ecology


	CAVE ECOLOGY IMPORTANCE OF CAVES Karst regions are notorious for environmental problems, and a knowledge of caves is one of the most important assets in being able to solve them. The most serious are described here: 1) land instability -- as caves enlarge, the overlying land tends to subside into them. This causes sinkholes, cracking of foundations and roads, disruption of pipelines, and diminished property values. 2) Problems of water supply -- most of the groundwater flow in a karst area is through caves. and unless these cave locations are known, the patterns of groundwater flow cannot be predicted. Well yield tends to be high (if solutional openings are encountered) or rather low. 3) Poor water quality -- the unfortunate thing about wells with high yield in cave areas is that their water quality is almost always low. Wells with smaller yield are generally of higher quality. Contaminants travel rapidly through caves and undergo very little filtering. Every effort should be made to avoid spills, leakage, or dumping of wastes in sinkholes. On a more positive note, caves give us information about the distribution of certain oil reservoirs and ore deposits. It is clear that a knowledge of caves is essential for a proper assessment of any of these phenomena. The study of caves is rapidly growing in importance, and only recently has it been recognized as a truly significant science of its own. CAVE CONSERVATION Every cave is sensitive, whether the cave is open to the public as a show cave or is an unexplored, wild cave. This fragile environment cannot repair itself like the environment on the surface. Because the cave is not visible to people living on the surface we often assume our actions will have no effect on the subsurface. This is as far from the truth as one can imagine. One of the most damaging environmental problems facing caves today is water pollution. Water is as vital to the life of a cave as it is to the life of humans. We have learned how caves are developed by groundwater seeping into the subsurface. Many caves also have rivers which start on the surface and enter the cave through a sinkhole or other entrance. Therefore, any materials that will dissolve in a liquid can enter the cave environment. Rain water and runoff carry pesticides from farming. Industrial wastes dumped into rivers may enter the cave if the river itself runs underground farther downstream. In many communities, raw sewage is pumped into caves with the idea that it will be cleaned up by the cave system. If any potential pollutant is allowed to remain on the surface over a cave, eventually, the pollutant will reach the cave environment. All of these factors will contribute to the destruction of the cave and any life present. An even more serious threat is to the water we drink. In western Wisconsin and eastern and southern Minnesota, much of the water we drink comes from aquifers which are riddled with caves. Much of the water that replenishes these aquifers comes from rainwater seeping into the ground. Caves provide a more direct route for the water to reach the water table through soil and rock. As a result, contaminants reach the water table in a matter of a few hours or days rather than months or years. In rural areas, people will have wells and septic systems. This also may be true of small towns and villages. It is not unusual to find a homestead or even a village or town pumping well water from the same rock unit as they dispose of the sewage. We must keep in mind that anything we put into the ground will eventually reappear in our drinking water. In one instance, dye flushed down the toilet in a house reappeared in the kitchen sink in less than 45 minutes. How much filtering has THAT water seen? CAVE ENVIRONMENT CAVE TEMPERATURE The temperature of a cave is directly related to the outside temperature. Rock is an excellent insulator but does allow some heat to enter into the ground and also be released. This is most evident during the spring when the ground thaws after cold winter. The ground temperature will slowly adjust to air temperature changes but this process takes thousands of years. Because the change is so slow, we find that the ground temperature is approximately equal to the average annual surface temperature. In other words, if you know the average daily temperature (in a 24 hour period) for each day of the year, add them all together (365 temperatures) and divided by 365 (number of days in one year), you will arrive at the annual average temperature. This number is approximately equal to the temperature in the cave, or ground temperature. This temperature will be influenced by where the cave is located both in altitude and where on the earth. The average temperature of caves in Texas is close to 70 degrees. Our cave is at 49-50 degrees. Wisconsin caves will average from 49-52 degrees depending on where in the state the cave is located. Crystal Cave can have temperature fluctuations of as much as two degrees depending on where you are in the cave and what the atmospheric conditions are at that time (more on that, later). Contrary to popular belief, the Refrigerator Room is not any colder than the rest of the cave. The temperatures of pools of water in the cave will also be equal to the temperature of the cave air. Any water entering the cave will be warmed or cooled to the cave temperature. The water dripping from the ceiling of the cave is 49 degrees. CAVE HUMIDITY The air in Crystal Cave is essentially saturated with water vapor which makes the relative humidity close to 100%. This high humidity is the result of moisture (water and carbonic acid) constantly seeping through the roof, walls, and floor of the cave. The constant temperature of the cave allows the high humidity to be maintained indefinitely. The only place humidity may be slightly lower is on the first and second levels. This is because the outside humidity is usually lower and the air on these two levels can be diluted through mixing with surface air. AIR CURRENTS Visitors frequently ask if the cave will ever run out of oxygen or if noxious gases like methane or carbon dioxide can build to the point of toxicity. In Crystal Cave the answer is NO! Most caves are very well ventilated and Crystal Cave is no exception. The cave is ventilated by exchanging air with the outside. This process is accomplished through the changing barometric pressure. Outside the cave, air is warmed during the day. As it warms it becomes less dense and the barometric pressure falls. When the outside pressure falls, the air flows out of the cave. At night the air is cooled, becoming more dense causing the pressure to rise. Air will be drawn into the cave during the night. Other pressure changes are related to the weather like those changes which accompany the passage of a storm front. These pressure changes are superimposed upon the daily fluctuation. The cave pressure adjusts to conform to the resultant effect of both. Temperature will also affect air movement. If the cave air is colder (more dense) than the outside, as in summer, the air will flow out of the cave through the lower Tree Fork Entrance into the gully, pulling warmer air in through the upper Service Entrance. If the cave air is warmer (less dense) than the outside air as in winter, air flow will be upward and out the upper Service Entrance and colder air will be pulled in through the lower Tree Fork Entrance. This type of air flow is similar to the “Chimney Effect”. The cave air is in constant motion as it attempts to adjust to surface changes. Usually these air currents are so slow that they can be detected only with barometers or very sensitive wind gauges. However, there are times when the air currents are quite obvious as light breezes and strong gusts moving through the Cave Door and the store’s stairwell.