Iowa is part of the Mississippi River Watershed. Students are familiar with how water and rivers eventually end up in the Gulf of Mexico. Students may also be familiar with groundwater and aquifers.

Shown here is Coldwater Cave in Winneshiek County. 

• The first video shows water falling into the cave and weathering the flowstone. The weathering appears to be washing the rock because it gets lighter in color. What is actually happening is the oxidized layer is being weathered and eroded away.
• The second image shows the eroded effect of the cave from tens of thousands of years of flood water entering and receding during periods of heavy rain. The rock at the bottom of the cave has jagged edges compared to the smooth walls above.
• The third image is a still water pool that shows sediment deposited in the bottom. This is an example of the sediment from the cave being deposited into this pool of water.

This particular phenomenon demonstrates how water transforms underground landmarks. Water in Coldwater Cave rises and falls when there is flooding activity from Minnesota down through Iowa. These flood waters weather the limestone walls eroding the sediment and depositing it elsewhere in the cave. Flooding also brings in mud and silt that changes the entire look of the cave. Water that falls inside the cave can weather the flowstone, erode the sediment, and deposit it elsewhere in the cave as well. Deposits of sediment over long periods of time form sedimentary rock.