Horcum Hole EarthCache
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THE HOLE OF HORCUM
The given coordinate's will take you to the carpark across from Horcum Hole. Please take care when crossing the busy road.
The hills around Horcum Hole are made up of Lower Calcerous Grit on top off Oxford clay .This spectacular amphitheatre was formed by rainwater seeping down through the pourous lower Calcerous Grit.
When the water reaches the impenetrable Oxford clay level, it is forced to the surface as a spring. The spring caused numerous landslides which have widened the Hole.
Lower Calcerous Grit comprise's clay,clayey sand's and sands which make it very porouus. During the Jurassic period the grit would have been low-Lying land.
Oxford clay is a Jurassic marine sedimentary rock. During the Jurassic period the Clay would have been a shallow sea.
During the Upper Jurassic, warm shallow seas covered much of the UK. Ammonites and marine reptiles swam over a seabed rich in corals and a wide range of shellfish. Over the next 165 million years, geological periods came and went, burying the Jurassic rocks deep below the earth until major earth movements, erosion and weathering exposed them to the surface again.
There are also glacial and post glacial deposits in the bottom of the hole. below is a list of deposits not all of these can be found in the bottom of the Hole
GLACIAL DEPOSITS
Dropstones:
These are curious-looking boulders bound in sedimentary deposits. They measure up to ten feet (3 meters) in diameter. It is believed that they were carried on drift ice and deposited where the ice melted. This place may have been covered by the sea at one time.
Drumlins:
These are aligned, elongated hillocks created from thick deposits of glacial till. They are composed of clay till and, sometimes, sand and gravel sediments. They are steepest on the side facing the glacier, and gently sloping on the other side.
Erratic Boulders:
These are rocks ranging in size from pebbles to massive boulders that have been strewn in mountainous regions. They have been carried by glaciers for 500 or more miles (800 km). An indicator boulder is a glacial erratic of known origin used to locate the source area and the transport distance of any given glacial till. A boulder fan is a fan-shaped area containing distinctive erratics.
Eskers:
These are long, narrow ridges of stratified glacial meltwater deposits of sand and gravel. They usually occur in areas once occupied by the ground moraine of a continental glacier. In length, they may extend up to 500 miles (800 km). However, they are seldom more tha 1,000 feet (303 meters) in width and 150 feet (45 meters) in height.
Frost Polygons:
These are seen as snow retreats in Arctic and alpine regions where the soil is exposed to seasonal freezing and thawing cycles. They create a honeycomb network. The shapes are a wide range of sizes, depending on their composition.
Glacial Varves:
These are regularly banded deposits, developed by cyclic sedimentation, with fine-grained, dark laminae alternating with coarse-grained lighter layers. They develop on the floors of cold freshwater lakes that are fed by glacial meltwater streams.
Kames:
These are low, conical mounds of stratified sand and gravel at the end of an ice sheet or the margin of a melting glacier. They form in similar places as eskers.
Loess Deposits:
These are windblown sediments that have accumulated in thick deposits of a finely-grained, loosely consolidated sheets. They are made up of particles of quartz, feldspar, horneblende, mica, and clay. They lie downwind from glaciated areas. Dune deposits of desert sand are found with them.
Moraines:
These are accumulations of rock material carried by a glacier and deposited in a regular pattern. The material ranges from sand to boulders. Ground moraine is an irregular layer of till deposited under a glacier. A terminal moraine is a ridge of debris deposited at the forward melting point of a glacier. A lateral moraine is the debris from erosion and avalanches along the edges of a glacier.
Tillites:
Glacial till is nonstratified material deposited directly by glacial ice. It is made up of clay and medium boulders. Tillites are sedimentary rocks formed by the compacting and cementing of glacial tills.
THE LEGEND
A more romantic Legend tells us that Horcum Hole was created when a giant named Wade, who was in fact a Saxon chief, grabbed a 'handful' of earth to throw at his wife, Bell - the soil missed its target and landed to form the 800ft high hill of Blakey Topping which lies about a mile to the east .
To log the cache please upload a photo of you or your GPSr with the Hole in the background and E-Mail me the answer's to the following question.
1) Estimate the depth of the hole
2) How many years ago was Lower Calcerous Grit created
Any logs without a photo will be deleted
Additional Hints
(No hints available.)