XENOLITH EARTHCACHE EarthCache
-
Difficulty:
-
-
Terrain:
-
Size: 
(other)
Please note Use of geocaching.com services is subject to the terms and conditions
in our disclaimer.
This cache is located on Greenville Technical College Campus. It has been placed with the approval and permission of the head of campus security. Please respect the property.
This cache is handicap and wheelchair accessible. A concrete walkway runs along the area, but you must cross some slightly uneven grassy area. Watch for fire ants in places!
A Xenolith (zen’-o-lith) is defined as a rock or a fragment of rock embedded in another kind of rock.
According to Wikipedia:
A xenolith (Greek, ‘foreign rock’) is a rock fragment which becomes enveloped in a larger rock during the latter’s development and hardening. In Geology, the term xenolith is almost exclusively used to describe inclusions in igneous rock, during magma emplacement and eruption. Xenoliths may be engulfed along the margins of a magma chamber, torn loose from the walls of an erupting lava conduit or picked up along the base of a flowing lava on the Earth’s surface.
According to a geologist I consulted, a xenolith can be as small as a pebble, or larger than “a Buick”. Xenoliths may be angular or round. They are present in most bodies of igneous rock.
To be considered a true xenolith, the included rock must be identifiably different from the rock in which it is enveloped. In contrast, an included rock of similar type is called and autolith or a cognate inclusion.
In appearance, there is usually a very distinctive difference in the two rocks. You will be able to see two or three types today.
******************************************************************************
TO LOG THIS EARTHCACHE DO AT LEAST *1* OF THE FOLLOWING:
(NOTE: Send your answer(s) to me in an email through geocaching.com the SAME DAY you log your find.) DO NOT POST YOUR ANSWERS IN YOUR LOG (Of course, if you use a photo as your proof of visit, it CAN be posted in your log).
You do NOT need to wait for a response from me.
1). Estimate the height of the Xenolith in the large rock outcropping at the coordinates. _____ Feet.
2). Using your compass or your GPS, determine the compass direction of the grain of the Xenolith part of the rock (for example, E-W (East West)).______
3). In your opinion, why might the direction of the grain of the Xenolith be different from that of the grain of the "parent" rock?________________________________.
4). Is the older rock the darker part or the lighter part? _____________ Optional: tell me what you can concluded from your answer._________
5). Send me the coordinates of one or more of the smaller Xenoliths nearby using your GPS to determine them. N ___ ___.______ W ___ ___.______
6). Do any of the other Xenoliths nearby appear similar in makeup to the one at the cache coordinates? ________. Optional: If so, how?___________________________________.
7). What can you conclude from the difference in the 2 rock types within one body of rock?______________________________________
8). While not required YOU MAY POST A PHOTO (OF YOU OR YOUR GROUP if you wish) (with your gps if possible) AT ONE OF THE XENOLITHS AS YOUR YOUR PROOF OF VISIT .
Please SEND YOUR ANSWERS in an email, NOT IN YOUR LOG!!
Remember - You only need to do *1* of the above to qualify for the cache.
You can, of course, do as many as you like.
******************************************************************************
NOW FOR THE CACHE
Follow your GPS to the posted coordinates. You will be looking at a very large rock outcropping. As you approach from the road, you will be looking at the end of the rock with a Very large XENOLITH. The western face of the rock can be seen to be very different from the top and eastern side. There is a distinctive demarcation line that is easy to see. These are actually two different kinds of granite gneiss, one of which is much older than the other.
While at a quick glance these may just appear to be the same, a closer look will show that they are very dissimilar, both in coloration, and in the run of the “grain” of the rock.
.
NOW, walk farther across the area. Here you can find some other xenoliths.
There is a very distinctive one, made up of gray rock with a white xenolith encased in it.
A little farther are two other fine examples of xenoliths, one comprising gray granite gneiss with one end incorporating a white rock made of quartz with some feldspar in it. In the photos I have laid my compass on them for scale.
Now that you know what to look for, see how many other examples you can find.
And remember to look for others when you go caching.
As a bonus, some of these rocks (look on the Large outcropping nearer the buildings) have small Garnets embedded in them. See if you can find them. They are burgundy in color and most are ¼ inch or so in size.
FTF HONORS GO TO . . .RobinMohawk!!!
Again, while optional, a photo of you and your GPS is always welcome, and CAN be used as your required question!
HAPPY CACHING ! ! !
| I have proudly earned the Geological Society of America's highest level: |
 |
Additional Hints
(No hints available.)