Lindley Hanson's Profile

established in 1941

9 miles of trails

ite in 1981

Biosphere Reserve in 1990

The great majority of caves are formed by the dissolving action of underground water as it seeps through the cracks in limestone. This particular limestone was originally deposited on the floor of a shallow sea that covered this part of the continent about 330-340 million years ago. At


Mammoth

Cave the limestone is capped by insoluble rocks, mainly sandstone, which form a resistant cap over the cavernous rocks below. This cap-rock helps to protect the upper-level passages in the cave from being eroded away. The rock layers are tilted an average of about 0.3 degrees toward the northwest (Figure 3).

he sandstone-capped region is called the Chester Upland

800 ft above sea level

Pennyroyal Plateau

e Pennyroyal Plateau

If a well encounters an active cave stream, there is usually plenty of water, but the water quality may be limited. The rapid flow of water, and the lack of filtering, allow contaminants to travel easily through cave passages. For that reason, most springs in cave regions are not reliable water sources.

As the Green River valley deepens by erosion, older passages lose their water to lower routes, which form new passages, while the older ones are left high and dry.

narrow and canyon-like

Where water is able to descend more or less vertically along fractures, vertical shafts are formed

Most passages that form below the water table have
tubular shapes with rounded cross sections and very gentle slopes

But tubular passages cluster at only a few elevations, which correspond to significant pauses in deepening of the

Green River valley. These elevations are most easily recognized by places where canyon passages (formed above the water table) change downstream to tubular passages (formed at or below the water table). Today these points cluster at about 500, 550, 600, and 690 feet above sea level (Figure 3). They provide clues to the drainage history of the major rivers of the region, including the Ohio River and its tributaries, the
Green River being one of them.

ormed by epigenetic processes

Epigenetic karst is formed by aggressive recharge descending from the land surface; hypogenic karst is formed by aggressive recharge ascending from ground water under artesian conditions.

 The shales shed most of their recharge laterally to surface streams, and recharge and karst development below shale outcrops is limited, although locally it may be well developed if fracturing prevails.

Hydrogeologically, flow pathways and cave passages tend to be aligned and to lie on near-horizontal bedding planes of slightly-tilted blocks (Brahana, 1997), or along near-vertical shafts that follow joints and fractures.