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Rhododendron Rock at Mount Rogers EarthCache

Hidden : 03/05/2009
2 out of 5
4.5 out of 5

Size: Size:   not chosen (not chosen)

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Geocache Description:

At the Grayson Highlands Park, park at the Massie Gap parking area (see coordinates). Take the Rhododendron Trail to the AT Trail (white blaze). You are heading toward the Thomas Knob shelter and then if you are going to the top, take the Mt. Rogers Spur Trail. This cache is approximately one half way to the summit. Difficult hike.

Rhododentron Rock

Many millions of years ago, the Appalachian Mountain chain was formed when North America was part of the supercontinent Pangaea. Huge tectonic plates pushing against each other caused an up rift and large land masses were ‘forced’ upward to form the mountains. During this time, subterranean (very deep) pressures broke through the surface to emit lava. Yes, lava as in volcanoes! Very few people know that this part of the Appalachian Mountains known as the Mount Rogers Chain is actually extinct volcanoes. Since the last eruptions occurred millions and millions of years age, there is a almost zero probability that there will be future eruptions. At one time, these mountains were much higher in elevation. During millions of years of erosion from wind and water the size has been reduced by much more than one half.


How do we know that volcanoes were here and created the current landscape? That is where geology comes in. Geologists have studied the rocks and minerals that are found in the Mount Rogers area. What have they found? No smoldering volcanoes, no flowing lava and no enormous gas/smoke plumes in the air were found. What was/is found is the aftermath of all of those events………! It is within those rocks that the ancient history can be determined. The rocks here and ‘our’ Rhododendron Rock are created by one thing, volcanoes. They are not sedimentary and few are metamorphic, they are igneous rocks from volcanoes!

The Formation Of Igneous Rocks

Just what is the nature of these igneous rocks including the Rhododendron Rock? Igneous rocks are either intrusive or extrusive. Intrusive igneous rocks are part of the super heated magma that remains below the Earth’s surface. On the other hand, extrusive igneous rock is emitted from the volcano to flow and/or fly onto the surface. By and large, these are the type of rocks found on Mount Rogers and compose the Rhododendron Rock.In order to illustrate the differing types of igneous rocks, please refer to the diagram below.

The Rhododendron Rock is part of the larger formation known as the Rhododendron Gap. As you are hiking up from Massie Gap toward the Mount Rogers summit, there more than one large outcroppings. While the trail takes you to the Rhododendron Rock you will pass other wonderful but unnamed outcrops. There is no reason why you cannot take side trips to observe and photograph them. All are the productions of very active volcanoes. Notice the rocks that you must climb and walk on. One day, they were molten lava and you wouldn't’t be touching them!

Be very careful during this hike. At times the footing is loose and very often you will transverse large boulders and slick surfaces. This is not a trip for small children and we do not recommend that you bring them. If they do accompany you, please go slow and add an extra hour or more each way. Taking your time and assuming you will want to go to the summit, plan for at least 5 to 6 hours at a minimum. The weather can and does change quickly so dress appropriately and be prepared for change. Wear good hiking boots and a hiking stick is a must! Bring lunch and leave the area just as you found it (CITO)!

Note: For you to claim credit for this Earthcache you must complete a couple of tasks. First, post a photo of you and your group with the Rock in the background and your GPSr in hand. If you do not want to show your face in the photo, an alternative is to photograph your GPSr pointing to the rock. Secondly, email us the answers to the following questions: (1). Estimate the height of the Rhododendron Rock (2). Carefully examine the Rock and tell us the colors that you observe and (3). From the above chart, our explanation of igneous rocks and your examination, which type of igneous rock do you to believe the Rhododendron Rock is? (Hint: look for the "R") A guess is allowed!

The description of this cache could not be completed without mentioning the Wilburn Ridge ponies. It is very likely that you will encounter some of them, as many are friendly to humans. Take a lot of pictures and enjoy them. You cannot, but you will want to take one home!

A Little Friend on Wilburn Ridge

This Earthcache was approved by the Geological Society of America

We have earned GSA's highest level:


Additional Hints (Decrypt)

Ebpx Ba!

Decryption Key


(letter above equals below, and vice versa)