A xenolith ("foreign rock" - xeno means foreign in Latin) is a rock fragment that becomes enveloped in a larger rock during the latter's development and solidification. 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 body of lava on the Earth's surface.
This xenolith is located in a granitic glacial erratic that was left partially buried when the Grand Boulevard park was built. Glacial erratics are stones and rocks that were transported by a glacier, and then left behind after the glacier melted. There are several xenoliths of varying sizes and all are located on the east side of the erratic. They may be seen from the trail but not from the road.
This xenolith is a piece of gabbro, a coarse-grained, dark-colored, intrusive igneous rock. Gabbro is the dark equavelent of granite.
The picture here is of a typical gabbro xenolith, but not the one on Grand Boulevard. This one is in California, but they are very common and may be seen in many places. If you walk up the stairs in the NV library, which are polished granite, you are walking on lots of xenoliths
Your task is to let me know the following. Send in your answers at the same time as logging via email or messenger.
1. What are the dimensions of the largest xenolith?
2. What shape is it roughly - a triangle, square, or round?
3. How many xenoliths do you see on the east side of the erratic?
Enjoy your walk along the grand bulevard. Photos of the area are welcome but not of the xenoliths.