This Earthcache will allow the geocacher to investigate the weathering of granitic rocks at the stunning Bells Rapids Park. Granite is an igneous rock formed deep in the Earth’s crust up to kilometres below the Earth's surface. Here, the granite has been eroded and deeply and intensely weathered over millions of years.
Granite contains two feldspars - orthoclase and plagioclase which weather to soft white-yellow clays and quartz which weathers away to quartz (huh… yep.. quartz is hard and typically breaks down through mechanical processes to become quartz sand).
Regolith Profiles over Granite
In some areas, thick zones of white clays form above weathered granites and may be covered with an iron cap of laterite and a thin soil. This is termed an intact regolith profile.
In areas where there is topography and the action of wind and rain, the iron cap and clays get eroded away to leave behind a very thin to absent soil cover and hard fresh grey granite. This is called a stripped regolith profile.
Now it’s time to be a geo and look at the rocks at ground zero. The questions will allow you to determine the regolith profile.
1. Feel and scratch the geology at GZ to determine how weathered the rock is. Is it soft or hard?
2. Are you looking at soft clay or hard granite? Describe what you see.
3. Is there much soil (typically has vegetation growing in it) or is it mostly clay or rock?
4. Based on these threeanswers, what type of regolith profile is present here? Soft white clays (intact regolith profile) or hard grey granite (stripped regolith profile)
5. Finally, a task is to take a photo of you or your GPS at GZ showing the view (not the geology) include the nearby tree.
You may log your find immediately but you will need to send your answers within 10 days to stop your log from being deleted.