Unit 6 – Mammoth Cave Mammoth Cave: A World Unknown to Daytime--That May Matter to Your Drinking Water Waterfall into historical entrance of Mammoth Cave. National Park Service Photo. aca/ENTRANCE.JPG aca/ENTRANCE.JPG All pictures in this slide show are by R. Alley unless otherwise indicated (as for this one).

Unit 6 – Mammoth Cave National Park Service Photo. Many cave creatures are uniquely adapted to their environment, which may seem strange to us but is normal to them.

Unit 6 – Mammoth Cave Here, a cave cricket sits on a limestone ledge in Mammoth Cave. (From tip of front leg to tip of back leg, the cricket is about 3 inches long.)

Unit 6 – Mammoth Cave National Park Service Photo. Broadway of Mammoth Cave is one of the many huge passageways dissolved in the layered limestone of the park. Roof collapses happen occasionally, as shown by the rubble on the right, but are rare, so tourists are considered safe.

Unit 6 – Mammoth Cave Cindy Alley (who prepared many of the graphics for the course) and friend Sue Croll in Mammoth Cave. The cave is immense; this room is several stories high.

Unit 6 – Mammoth Cave Gypsum flowers, Mammoth Cave (photo about 6 inches across). Limestone (calcium carbonate) often has a little gypsum (calcium sulfate), which makes formations with this distinctive appearance.

Unit 6 – Mammoth Cave Channels in limestone, Mammoth Cave (photo about 2 feet across), produced by dissolution of limestone in acidic groundwater.

Unit 6 – Mammoth Cave Passage in Mammoth Cave. This probably started as a vertical crack, which was widened by dissolution of the limestone rock into acidic groundwaters flowing along the crack.

Unit 6 – Mammoth Cave Frozen Niagara section of Mammoth Cave. More groundwater enters this region than in the rest of the cave, because the sandstone “lid” that covers much of the cave is broken here. The water picks up extra carbon dioxide in soil, dissolves limestone, then loses the extra carbon dioxide to the cave air (which exchanges rapidly enough with the outside to exhaust the carbon dioxide), and deposits the dissolved limestone as cave formations.

Unit 6 – Mammoth Cave Water often enters along cracks; a line of hollow stalactites (“soda straws”) is arrowed in the upper left. The greenish color just below that line comes from algae growing where a Park Service light provides a little energy.

Unit 6 – Mammoth Cave Mammoth is not alone among Park Service Caves. This is Carlsbad Caverns. Wind Cave, Jewel Cave, and others are equally beautiful.

Unit 6 – Mammoth Cave The sandstone cap that prevents collapse of Mammoth and allows the cave’s immense length does reduce drip-water entry and thus cave formations, so other Park Service caves are often prettier than Mammoth. This roughly 20- foot-high feature is in Carlsbad Caverns.

Unit 6 – Mammoth Cave Fossil snails (gastropods) in limestone, Cades Cove, Great Smoky Mountains National Park. Most caves and sinkholes are in limestone, and most limestone started out as shells or skeletons of marine creatures. Many shells are so broken as to be unrecognizable, but quite pretty fossils can be found. Areas/smokys/cadesCove/GISData/bymap/gastropod &operculae.htmhttp://geology.er.usgs.gov/eespteam/smoky/Research Areas/smokys/cadesCove/GISData/bymap/gastropod &operculae.htm USGS Photo

Unit 6 – Mammoth Cave Soil on limestone bedrock in excavation for a basement, State College, PA. The rock layers slope down to the lower right, and are curved a little. Dissolution has enlarged cracks and deepened some places more than others. When the deeper places become big enough, we say a sinkhole has formed.

Unit 6 – Mammoth Cave Another view of State College, PA soil over limestone, revealed in an excavation for a basement. A small sinkhole has formed to the right, where the redder soil dips down past the whiter stone.

Unit 6 – Mammoth Cave USGS Photo. Sinkhole near Shenandoah National Park. The center of the hole is just to the right of the right-most person. The ground slopes into the hole from all directions, so rainwater that runs in and does not evaporate must go downward through the bottom of the hole.

Unit 6 – Mammoth Cave Sinkhole in limestone, Cades Cove, Great Smoky Mountains National Park. The sinkhole is the dip containing tree trunks in the foreground. Sinkholes most commonly form by dissolution of limestone along joint intersections, but cave-roof collapse also may form sinkholes. Here, tree trunks have fallen in, but in many places people have dumped things in, which go right to the groundwater. adesCove/GISData/bymap/sinkholesb.htm, adesCove/GISData/bymap/sinkholesb.htm, USGS Photo

Unit 6 – Mammoth Cave Sinkholes in limestone near Gregory’s Cave, Cades Code, Great Smoky Mountains National Park. Similar scenes are common along the Appalachians in many places. Soil, rocks, leaves, etc. fall into such holes, yet the holes are not full, indicating that materials are sinking toward the groundwater. earchAreas/smokys/cadesCove/GISData/byma p/sinkholes.htmhttp://geology.er.usgs.gov/eespteam/smoky/Res earchAreas/smokys/cadesCove/GISData/byma p/sinkholes.htm USGS photo