A Turtle's Back Rock Formation EarthCache
A Turtle's Back Rock Formation
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The Turtle Back Rock ares is nestled within the 2,000 acres of the South Mountain Reservation, South Orange, NJ. Park off Walker Rd, Follow the orange/white to the rock formations.
The Turtle Back Rock area was named after a rock formation which resembles the back of a turtle shell. All of the boulders and rocks in this area have the same hexagonal lines and markings etched into the surface.
Basalt lava once flowed through the Newark rift Basin valley. When the basaltic trap rock cooled, it fractured into small hexagonal blocks. Minerals filled in the cracks and voids before it was covered again. Natural erosion wore away the basalt faster than the minerals. The result was a rock pattern similar to a turtles shell.
An article can be found in Weird NJ magazine, Vol. 11 page 48. Please watch you step around the cliffs and rock formations.
Brief explanation: Basalt is the usually hard and black volcanic rock formed from (liquid) basaltic lava. Basaltic lava contains less than about 52 percent silica (SiO2) by weight. Because of its low silica content, it has a low viscosity (resistance to flow). Therefore, basaltic lava can quickly and easily flow more than 20 km from a vent. The low viscosity typically allows volcanic gases to escape without generating enormous eruption columns, although basaltic lava fountains and fissure eruptions, however, still can be hundreds of meters tall. Basaltic lava is erupted at temperatures between 1100 to 1250°C. Basalt is by far the most common volcanic rock type. Basaltic magma is formed by partial melting of material from the upper mantle, and and is therefore typical for volcanism at hot-spots and at rift-zones. In these areas, upwelling of the mantle (either caused by a rising mantle plume underneath hot-spots, or by a divergent plate boundary at mid-ocean rift zones) decreases the pressure of the hot rock and therefore causes (partial) melting. Oceanic crust and submarine volcanoes consist largely of basalt, because most of them are formed at rift-zones (all ocean floor) or hot-spots. Among subaerial volcanoes, basaltic lava is primarily found at shield volcanoes. Basaltic lava flows can be subdivided into two end-member structural types, according to their flow surfaces:-- Pahoehoe lava - smooth, billowy, or ropy surface.-- A'a' lava - fragmented, rough, sometimes spiny, or blocky surface... The Newark rift basin contains Triassic and Jurassic rocks deposited in a large sedimentary basin that formed during the breakup of Pangea. The giant continent that existed about 250 to 200 million years ago. The Newark basin forms the largest physiographic province (Piedmont province) in the northern half of New Jersey. Because the Newark basin makes up more that 95% of the Piedmont province, most geologists simply refer to this area as the Newark basin. The rocks within the Newark basin consist predominantly of siltstone and shale, along with sandstone and conglomerate. Most of these rocks have a reddish color, which gives the soils in the Newark basin a reddish hue. The Newark basin also contains lava flows and intrusions, the largest and best known of which is the Palisades sill. [A fault is a break or fracture in the Earth's crust along which movement takes place.] Newark Basin Info: (visit link)
Nature has a way in manifesting and representing itself in many ways. The same shapes and lines appear in all living and non living parts in Nature and this great Earth.
This "Turtle Back Rock" Earthcache example demonstrates one similarity in nature, whereas the lines of a simple living box turtle are duplicated in thousand year old rock formations.
EARTHCACHE.ORG GUIDELINES FOR LOGGING AN EARTHCACHE:
EarthCache sites must provide Earth science lessons. They take
people to sites that can help explain the formation of landscapes
or to sites of interesting phenomena such as folds, faults,
intrusions or reveal how scientists understand our Earth (such as
fossil sites etc.) EarthCache sites must be educational. They
provide accurate but simple explanations of what visitors will
experience at the site. Logging of an EarthCache must involve
visitors undertaking some educational task that relates to the
Earth science at the site. This could involve measuring or
estimating the size of some feature or aspect of the site,
collecting and recording data.
To log your Earthcache you MUST follow the following guidelines:
Please bring a sketch pad and pencil.
1. Spend time studying the turtle back rock formations and find 3 different turtle rock shell surfaces that you feel resemble a real turtle back shell.
Note: Bring a picture of an actual turtle back shell for comparison.
2. Then search the rock formations and locate a turtle rock shell formation which has the most sides.
Example: the center of the Box turtle shell has 8 sides.
3. Sketch your 3 Turtle back rock shell formation choices, and your multi sided formation choice, (write the number of sides in the center of your sketch).
4. Take a photo of your sketch and post it with your log visit.
5. You MUST take a photo of you and or your group, include the Turtle Back Rock formations in the photo.
Additional Hints
(No hints available.)