|Geology:||(click on an image for a larger view)|
Crabtree Cave is
developed along vertical or steeply dipping joint planes in the Greenbrier
Limestone, which is cross bedded and light gray to tan in color. Arenaceous
limestone and red shale beds are mixed with the purer limestone. The beds
strike N. 60º E. and dip 15º E. Joints striking N. 30º
W. (dip 80º N.), N. 50º W. (dip vertical), and N. 50º E.
(dip 80º N.) are developed in the limestone.
Cave is not only the largest cave in Maryland, having 4200 feet of passage,
but is also perhaps the most difficult to explore. The cave can be traversed
as a circuit or loop, via the connection tube, by competent and thin explorers
in an average time of 6 to 10 hours. It typically consists of high, irregular
fissure passages which are constricted at varying levels, thereby necessitating
much chimneying, crawling, and squeezing. A 50-foot length of rope is needed
to negotiate a drop in the left passage when heading east.
The entrance is a cleft 2 feet wide that drops 10 feet to the cave floor. A narrow, irregular fissure passage, 3 feet to 5 feet wide and up to 40 feet high, slopes gently to the southwest for 120 feet to a junction room, over 50 feet high. From here the two main passages of the cave diverge. One may enter either passage and follow a circuitous route through the cave and return via the other passage. The passage leading west (right passage) is a high, coral-lined fissure. A stream flows from it across the junction room and descends into a sewer or stream channel at the base of the left passage. A ledge with a 15-foot overhang must be climbed in order to enter this section.
The right passage terminates in a breakdown room which is apparently close to the surface as judged by the presence of roots in some places. About 200 feet before the end of the right passage is a low 100 foot long crawlway, the connection tube, which leads to the left passage. Midway between this junction and the entrance is the Map Discovery Passage, which leads southwest for about 600 feet. About 350 feet further along the left passage (towards the entrance) is an inconspicuous hole leading into the Algonquin Passage which connects with the old mine near the entrance via the "Handshake Hole". The lowest point in the cave is in this passage (40 feet below entrance), and the highest point is at the end of the right passage (163 feet above entrance). The cave therefore has a vertical relief difference of over 200 feet. Streams flow along the floor in both main passages, with a general circulation down dip to the east.
Numerous pack rats (Neotoma) make camping and exploring in this cave quite interesting. In recent years, however, a marked decline in their population has been observed.
(from ES3 -Caves of Maryland)
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