The Geology of the Shawangunks
The Shawangunk Conglomerate extends from High Point, New Jersey
and across the Deleware Water Gap into Pennsylvania (called the
Kittatinnny range), as well as south to West Virginia (North Fork
Mountain and Seneca Rocks) to Alabama. Only near New Paltz and
Seneca Rocks are the rocks durable enough for a major rock climbing
area.
The Shawangunk Mountain's bedrock consists of two formations:
the Shawangunk Conglomerate, which makes up the cliffs so popular
with rock climbers, and the Martinsburg Formation, which is mostly
shale that you may see below the conglomerate. The shale was formed
when layers of clay and silt accumulated at the bottom of a sea
about 465 million years ago. These sediments hardened into shale.
The sea water disappeared when the region was uplifted.
About 420 million years ago, a shallow sea spread across a level
landscape of eroded shale. Rivers carried pebbles and quartz sand
grains which were laid down as gravel layers. As this gravel was
buried under piles of younger accumlations of sediment, the weight
of the overlying sediments transformed the gravel layer into
Shawangunk Conglomerate. This conglomerate has a natural "cement"
of quartz which holds the quartz particles together, to form one of
the hardest and most durable of rocks. The Shawangunk Conglomerate
is very hard and resistant to weathering; whereas the underlying
shale erodes relatively easily. A good place to see the dark
crumbly shale formation is on Route 44/55 across the street from
the scenic overlook.
About 350 million years ago, a collision between the African and
North American tectonic plates of the earth's crust created an
uplift that deformed and raised the Shawangunk Mountains, causing
extensive folding and faulting.
Millions of years of erosion have worn down the upper layers of
limestones and shales which dissolved and crumbled more easily than
the quartz conglomerate, leaving the Shawangunk Conglomerate
exposed as the top layer. When the glaciers came through during the
ice ages, the ice ground across the ridge, removing the ancient
soils, exposing the bedrock surfaces, carving grooves and
striations on the bedrock by pebbles and boulders imbedded in the
overriding ice, and leaving occasional erratics - boulders left as
the ice melted away. Once the rocks age and become hard and
brittle, crustal movements can cause them to break along cracks or
joints. Water freezing within these joints over time creates a
wedging action that creates blocks that move apart and sometimes
fall off the cliff. These cracks enable the plethora of excellent
climbing routes on the cliff face.
Here, uphill from the cache, you can see the exposed bedrock
tilting upwards, along with occasional erratics. If you
theoretically continued uphill, you'd be walking on the top of the
Trapps cliff, eventually finding the cliff edge (but don't try
this, there are no trails in this area and off-trail use is not
permitted).
The Cache
The cache is an ammo box hidden on the side of the Overcliff
carriage road, there is no need to bushwhack. It is filled with
"rock" related items. Once you get on Overcliff Road, the hiking is
on a flat gravel carriage road which can easily be hiked, jogged or
bicycled.
Parking
The closest parking area for this cache is the West Trapps
Parking Lot. Going west from New Paltz on Rt. 44/55 past the
hairpin turn and the Trapps Bridge overpass, you will find the West
Trapps Parking Lot on the right. An easy trail takes you from the
end of the parking lot to the junction of the Undercliff/Overcliff
Road carriage roads, where you will also find a port-a-potty. At
the top of the steel bridge, go to the big boulder in the middle of
the trail and turn left at this junction to travel the Overcliff
Road. On busy weekends, especially in the autumn, finding parking
can be difficult. Best bet is to arrive before 9am or late in the
afternoon. Note: Parking at the scenic overlook is limited to 30
minutes.
About the Mohonk Preserve
The Mohonk Preserve is a private land conservation organization
established to protect the Shawangunk Ridge, it is not public land
funded by the government. Therefore, there is a day use fee to use
the preserve which funds its maintenance and programs. For the
current day pass fees, check the Mohonk Preserve
website. Note that dogs must be leashed at all times.