(LEVELS C & D)
The “Historic tour” and “River Styx tour” allow visitors to examine Mammoth Cave's deeper passages at levels C, D, E, and F. Access is via a descending narrow passage behind Giant's Coffin in the Main Cave (= level B). The upper levels are the oldest (the first ones to be dissolved out, when the water table was at a much higher level). Below the level of the Main Cave, the passages get progressively younger. Levels C and D are dissolved out in Ste. Genevieve Limestone beds. Levels E and F are partially to entirely developed in the next formation down - the St. Louis Limestone (mid-Meramecian Stage, middle Middle Mississippian).
Levels deeper than the Main Cave are usually accessed via Dante's Gateway, a narrow, descending passage behind Giant's Coffin. It acted as a water drain for level B's Main Cave long ago. Dante's Gateway brings you to the Wooden Bowl Room, named after an artifact found here in early days, although some say the name is in reference to the shape of the room.
Wooden Bowl Room (looking ~S) (above & below) - these photos show the southern portion of the Wooden Bowl Room. The room is ~rounded in plan view and has a moderately low ceiling. It is situated at Mammoth Cave's level C.
The ceiling is limestones of the Karnak Member (Ste. Genevieve Ls.), a unit which consists of oolitic and fossiliferous limestones having some patches of sparry calcite. The walls of the room expose the Spar Mountain Member (Ste. Genevieve Ls.), a unit having dolostones/dolomitic limestones and sandy limestones.
The opening at the base of the wall (called the Snake Hole) leads to Jessup Avenue, Flint Alley, and Ganter Avenue, none of which have been publicly accessible since the 1940s. The Jessup, Flint, and Ganter cave passages have been considerably defaced by prehistoric American Indians, late 1800s cave trail construction, and by historic cave tours. All three passages have a relative abundance of American Indian artifacts and other evidence of Indian activity, such as gypsum & chert/flint “mining”. A prehistoric Indian latrine was discovered by archaeologists in Ganter Avenue.
Wooden Bowl Room - level D is accessed by descending these very steep stairs at the northeastern side of Wooden Bowl Room. This descent goes through the Fredonia Member (Ste. Genevieve Ls.), a unit which has a mix of micritic limestones, argillaceous limestones, oolitic & fossiliferous limestones, and dolostones/dolomitic limestones. This descent is called the Steeps of Time (also known as the Dog Hole).
The Steeps of Time ends in a tubular, phreatic passage called Black Snake Avenue, developed at Mammoth Cave's level D (upper level D).
Black Snake Avenue (looking ~N or ~NW) - the ceiling and walls of this tubular passage are nicely scalloped for much of its length. Scallops are dissolutional features formed at or below the water table (in the phreatic zone). They vary from being scoop-shaped to broadly ripple-shaped. They indicate dissolution in flowing water (an underground river or stream). Flow direction was toward the steep side of the scallops (= into the photo shown above). The rocks are part of the Fredonia Member (Ste. Genevieve Ls.).
Black Snake Avenue - nice rills on Fredonia Member limestones along the walls of Black Snake Avenue. Rills are dissolutional features formed by water flowing down sloping rock faces in the vadose zone (above the water table). As such, these rills postdate the development of the passage and the scallops (both of which are dissolutional phreatic features).
Black Snake Avenue - Fredonia Member rocks with solution pockets in the lower part of the photo & rills in the upper part of the photo.
Two significant domepits (aka vertical shafts) are encountered along Black Snake Avenue - Sidesaddle Pit and Bottomless Pit. Domepits appear to be pits when viewed from above, and would be called domes if viewed from below. Hence the term “domepit”. Domepits are dissolutional features formed in the vadose zone (above the water table). They form as vertically-descending water dissolutionally enlarges joints or joint intersections.
Sidesaddle Pit - Fredonia Member limestones line the walls of this impressive domepit. The vertical grooves seen on the walls of Sidesaddle Pit and Bottomless Pit (see below) are called flutes. They are similar to rills (see above) by also being dissolutional vadose features, but flutes are grooves on vertical limestone walls, while rills are grooves on sloping limestone walls. The rubble-covered floor of this domepit appears to bottom out in the lower Ste. Genevieve Limestone (Fredonia Member) or the upper St. Louis Limestone.
Bottomless Pit (from an old postcard; original photograph by Benjamin Hains)
Bottomless Pit (above & below) - a very deep domepit that bottoms out well into the St. Louis Limestone (the lowest encountered stratigraphic unit in Mammoth Cave). The limestone walls of the domepit are nicely fluted. The rocks seen here & below are Fredonia Member limestones (Ste. Genevieve Ls.). Bottomless Pit used to be a turn-around point for early tours. Later tours crawled along a narrow edge. The domepit is now readily traversed via a metal trail bridge.
This domepit does have a bottom, despite the name. The rubble-covered floor of this domepit is in the upper St. Louis Limestone. The floor closely coincides with the level of the River Styx and the Echo River (the modern water table; aka local base level).
Black Snake Avenue between Bottomless Pit and Winding Way continues to be a subhorizontal phreatic cave passage having an ellipsoidal cross-section shape. This is still part of level D. The rocks are Fredonia Member limestones (Ste. Genevieve Ls.).
Scotchman's Trap (from an old postcard) - breakdown occurs at a small opening called Scotchman's Trap where Black Snake Avenue descends a bit elevationally & stratigraphically.
One of the most famous passages in Mammoth Cave is a quite narrow, tapering-downward, twisting canyon passage called Winding Way. The park service uses the anti-male sexist term “Fat Man's Misery” for this locality (in fact, objections to this name have been made for over a century). Part of this stretch has also been called “Tall Man's Agony” (uncomfortable stooping is necessary for tall folks). Winding Way is developed in about the mid-Fredonia Member (Ste. Genevieve Ls.).
Winding Way - this remarkable canyon passage is about half-a-meter to a meter wide in the lower part (where people's legs are). It's a bit wider in the upper part. In places, it's about a meter-and-a-half tall. Notice the scallops along the limestone walls.
Some claim that no one has ever gotten stuck in this passage. Bullitt (1845) recounts the following: “our fat friend, who was puffing and blowing behind us like a high pressure engine, cried out, ‘Halt, ahead there! I am stuck as tight as a wedge in a log!’ Halt we did [and we looked] at our friend, who was in truth ‘wedg’d in the rocky way and sticking fast,’ . . . the imprisoned gentleman soon burst his bonds. . . and at length forcing his way into Relief Hall, he cried out, in the joy of his heart, while stretching himself and wiping the perspiration from his jolly, rubicund face, ‘never was a name more appropriate given to any place - Relief. . . I can now breathe again.’”
Winding Way was formed by moderately fast-flowing water draining toward the old water table.
Winding Way ends at a moderately large, subhorizontal phreatic passage called Great Relief Hall (formerly known as Relief Hall). This passage is stratigraphically & elevationally lower than Black Snake Avenue and Winding Way, but is still part of Mammoth Cave's level D (= lower level D).
Great Relief Hall (looking WNW) - this is a phreatic passage, formed at or below the old water table. Flow direction of the underground river at that time was into the photo (toward the WNW). The light gray rocks of the ceiling and upper walls are Fredonia Member limestones. The darker rocks in the lower part of the walls are Fredonia Member dolostones/dolomitic limestones. Notice the scallops along the walls (the wavy sculpturing). Notice also chert nodules protruding from the ceiling. Chert is composed of cryptocrystalline quartz. So, it is highly resistant to weathering, erosion, and dissolution by slightly acidic groundwater.
Chert nodule protruding from ceiling limestones of the Fredonia Member (Ste. Genevieve Ls.) in Great Relief Hall (lower part of Mammoth Cave's level D).
Ceiling smoke writing (above & below) - Gothic Avenue is the not the only passage in Mammoth Cave that's been considerably defaced. The ceiling of Great Relief Hall also has a fair amount of smoke signatures. Note the 1839 and 1855 dates.