GC23KG7 The Split-Sphinx Rocks on Grandfather Mountain (Earthcache) in North Carolina, United States created by Konnarock Kid & Marge

GC23KG7 ▼

A cache by Konnarock Kid & Marge Message this owner

Hidden : 2/3/2010

Difficulty:

Terrain:

Size: Size: other (other)

Join now to view geocache location details. It's free!

Watch

How Geocaching Works

Please note Use of geocaching.com services is subject to the terms and conditions in our disclaimer.

Geocache Description:

This EarthCache will take you to the Grandfather Mountain Park located off of Highway 221 near Linville, NC. During inclement weather, be sure to check for Park Closings at: Phone 800-468-7325

Many thanks to the Park Naturalist staff for their help and permission to list this EarthCache. Please visit the Grandfather Mountain web site prior to making your visit: http://www.grandfather.com/

Summer Flora By The Rocks
The Blue Ridge Mountains of Western North Carolina and Eastern Tennessee are the result of the action of plate tectonics. This shifting of the plates occurred during what is termed the The Alleghenian orogeny. The Alleghenian orogeny is one of the geological mountain-forming events (an orogeny) that formed the Appalachian and Blue Ridge Mountains. Approximately 350 million to 300 million years ago, in the Carboniferous period, Gondwana (later to become Africa) and what became North America collided, forming the super continent, Pangaea. This collision exerted massive stress on what is today the Eastern Seaboard of North America, resulting in a large-scale uplift of the entire region. During this orogeny, some volcanoes occurred as found at the nearby Mount Rogers and Whitetop Mountains, but there is no evidence of volcanic action here at the Grandfather Mountain.

Pangaea

Grandfather Mountain is at the heart of a geologic wonder known as the Grandfather Mountain Window, a region covering several hundred square miles in northwestern North Carolina. During the Alleghenian orogeny as discussed in the above paragraph, vast sheets (the crusts) of rock were pushed over each other. The Blue Ridge Thrust Sheet moved more than 60 miles to cover what is now Grandfather Mountain. Many geologists believe that these mountains were once much, much higher than they are now. Erosion over millions of years has opened a "window" where younger rock shows through. The window is like a sack of potatoes with a hole in it. The potatoes are the younger rock and the sack is the older rock. Having this window permits the study of the sequence of rocks ranging in age from old to young. .
Grandfather Mountain also holds the distinction over other southern mountain terrains as having the most outcrops and boulders. The earlier mentioned erosion that occurred over hundreds of millions of years has carried away most of the rocks to form thick layers of sediment all across the Piedmont, Coastal Plain, and in the Atlantic Ocean. So, Grandfather's loss was other areas gain!

The Rocks
The rocks you will find on the Grandfather Mountain are basically metamorphic which is one of the three major rock groups. The other two of the three are sedimentary and igneous. Great pressure, heat, and the introduction of new substances cause metamorphism which changes the basic nature of the ‘mother’ rock. Changes include the development of new minerals, making the rock, which has been deeply buried and compressed, look very different from the original rock. At the Split Rock and the Sphinx Rock you will encounter metamorphosed conglomerate. The rocks are referred to as metaconglomerates.

The Split Rock
Now just where did these wonderful and very large bounders come from? They are certainly not ‘outcrops’ as found at the top of the Mountain. As we said earlier, they couldn’t be a result of volcanic action because there were no volcanoes here! So, just where did they come from? The most likely origin of the Split Rock and the Sphinx Rock was the top of Grandfather Mountain. Thousands, maybe millions of years ago, the bounders broke from the upper outcrops on Grandfather Mountain and fell (rolled?) to their current resting places. Before arriving at their current locations the rocks were most likely underwater. The type of rock (metaconglomerate) also means they were created millions of years ago as a stream bed in a previous mountain formation that likely pre-dated the current Appalachians. Unlike the Appalachian and Blue Ridge Mountains, the rocks are thought to be over 650 million years old!

The Sphinx Rock

The split in Split Rock occurred over many, many winters. It all began as a small crack that allowed water to seep into the rock. After repeated freezing and thawing, the split grew to it’s current size. Be sure to carefully observe the split. Later, you will need to answer a question regarding the crack.

NOTE: In order for you to claim a find of the Split and Sphinx Rocks you must email answers to the following questions: 1. Estimate the height and width of both rocks. 2. After carefully examining the ‘crack’ in the Split Rock, estimate the average width of the split. 3. Find the nearby sign and give the estimated weight of the Sphinx Rock. Last, please post a photo of the two rocks. While the photo is necessary and it would be nice, you do not have to appear in the picture. The Grandfather Mountain Park has many wonders to see and do. There are miles of trails and several picnic areas to enjoy. Also, be sure to visit the Nature Museum and the animal habitat. Take care and have fun.

We have earned GSA's highest level: