Earth Science Unit StudyWeek 15: We did three activities to explore how water moves underground.
Beneath the surface water flows down through the soil. In some places there are underground rivers, lakes and streams. Once water reaches the water table, it can even rise through the soil.
Following chapter 22 in Janice VanCleave's A+ Projects in Earth Science: Winning Experiments for Science Fairs and Extra Credit we explored how water percolates down through soil, how capillary action enables water to move up through the soil just above the water table, and how an aquifer or oasis forms even in very dry regions such as a desert.
The Water Table
Rising Water - Capillary Action
Because there is a molecular attraction between liquids and solids, liquids can defy gravity and rise into small spaces. Seeing colors run up through coffee filter paper dipped in water, water rising into a paintbrush, and surface tension are other examples of this phenomenon.
After a few minutes the water could be seen rising above the level in the dish.
A Desert Oasis
It's so strange the way an oasis can pop up in the middle of a dry desert. Water is trapped beneath the surface in many locations throughout the desert. With an impermeable layer both above and below it cannot get out unless it finds a crack.
If I had this to do over again, I may have used plastic wrap below and above the sand layer to ensure it was impermeable or perhaps used some craft foam to serve as the impermeable layers.
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