Crystal Canyon Natural Area is a geology lover’s paradise in the heart of North Arlington. It contains a very diverse geologic profile with evidence that suggests a near-shore marine environment might have existed at one time. Marine shales, siltstones, mudstone containing inner beds of calcareous fossil clams, gypsum layers and fine grain sandstone have been found there.
The Canyon
The canyon has been created over time by seasonal streams. Seasonal streams are ones in which the water only flows during the wet periods of the year. The streams here are tributaries of the Trinity River. As the waters rise and rush through the canyon, they erode the bedrock and carve a deeper groove into the canyon floor. At stage 1, you can observe the result of these forces.
The Crystals
Formed mainly by the evaporation of seawater, gypsum (calcium sulfate) can be found in a variety of shapes and forms. It can be soft, granular and white. This is the form used in sheet rock. It can also be found in its white, fine grained variety known as alabaster. At Crystal Canyon, you will find the crystalline form of gypsum known as selenite. These selenite crystals are transparent, monoclinic crystals that can be extremely beautiful. In fact, selenite is named after Selene who is the Greek goddess of the moon. At stage 2, look around the sides of the trail for these crystals.
To claim credit for this EarthCache, please send the answers to the following questions. DO NOT INCLUDE THE ANSWERS IN YOUR LOGS. Logs posted without providing answers to the questions will be deleted.
1. At stage 1, describe the status of the seasonal stream in this part of the canyon. Is there water present? If so, estimate how deep it is. If not, estimate the depth of the canyon from where you are standing.
2. At stage 2, how does the soil here compare to canyon at stage 1?
3. At stage 2, look around for a crystal of any size. Is it transparent, transluscent or opaque? What is the shape (regular or irregular)?
Optional send/post a picture of a crystal you found.