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mix of clay- to boulder-sized material.
5 basal till
planar beds of gravel and sand
inclined beds of sand and some gravel
laminated beds of silt, clay, and
very fine sand 0 1
vertical exaggeration x20 moraine
1 delta delta GL
3 debris bands 4
4 lacustrine fan
3 vel lake le bed rock IER AC meltwater
stream 4 ottom
lake b 1
5 1 Figure 13. Block diagram showing the depositional setting of glacial sediments
with photo insets of till and outwash. 18 at the glacier’s base (fig. 13). Overlying this lower compact till is
a thin, discontinuous, loose, poorly sorted silty sand and sand
containing as much as 35 percent pebbles, cobbles, boulders, and
lenses of sorted sand, gravel, and silt. Overall, stones are typically
more angular than those in the underlying till. This material is
debris that was released from the glacier by melting at the glacier’s
terminus. It may have been let down slowly by melting ice or flowed
off the ice onto adjacent land. This material is called ablation till
and flow till respectively (fig. 13). Frost heaving, burrowing animals
and insects, and root growth have also altered the upper few feet of
till making it less compact, and reorienting its stones.
A glacial erratic is a rock, commonly a boulder, that was picked
up and carried by the glacier and deposited some distance from its
source, often many miles. Most erratics show evidence of glacial
erosion by their subrounded shape, flattened sides, and striated or
polished surfaces. They are found throughout the park and were
largely plucked from nearby outcrops on Kittatinny Mountain and
in Kittatinny Valley. A few are larger than 10 feet in diameter.
The most remarkable are the Martinsburg sandstone boulders that
were carried up and out of Kittatinny Valley to the top of Kittatinny
Mountain. There they rest, as much as 900 feet above the valley
Landforms in the park that were created by the glacier include
drumlins, end moraines, and kettles. Drumlins are oval-shaped
hills consisting of till that were deposited at the g...
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