A cache by ksseeker47 Message this owner

Hidden : 7/8/2025

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Size: Size: other (other)

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Geocache Description:

This is a special type of geocache called an EarthCache. There is no container to find, but rather a location where you can learn an earth science lesson. To claim a find for this cache, please do the following:

Read the lesson below.
Visit the location and observe the geological forces in action. Be careful though, the rocky area can be slippery in places.
Send me the answers to the questions listed at the end of the lesson. You can send the answers via e-mail or use the GC messaging feature. Be sure to submit your answers within a couple days of logging the EarthCache. Group answers are fine, just list the members of your party with your answers. Do not post the answers to the questions in your logs.
Post a photo of yourself or a personal item at the waterfall overlook location. You can send this directly to me or attach it to your log.
Practice CITO by picking up at least one piece of trash while you are there. (This is technically optional, but why not?)
Also optional - try to observe plant and animal life in the area. You may be surprised at what you will see if you look closely.

Grand Falls

Grand Falls is the largest continuously flowing waterfall in the state of Missouri. The falls are also a great place to see how rock and moving water shape the land over time. When you look closely at the rocks here, you can see evidence of ancient seas, powerful erosion, and the unique properties of the predominant rock in the area called chert.

Rock Ledge

The waterfall drops about 12 feet over a wide ledge of chert. Chert is a very hard, gray or tan rock made mostly of microscopic crystals of quartz. Chert forms when tiny pieces of silica settle out of seawater and harden over millions of years. Long ago, this area was covered by a shallow sea. Sediment piled up on the sea floor, and over time, it turned into layers of limestone and chert. The chert layers are much more resistant to erosion than limestone which is the very reason this waterfall exists. The softer rock around the chert wore away, leaving the ledge we see here behind.

Grand Falls showing the resistant chert ledge

Erosion and Change

Shoal Creek, the stream that feeds Grand Falls, has been slowly eroding the rock beneath the falls. As water rushes over the ledge, it wears down the base of the waterfall. Over long periods, this can create undercutting, where the rock underneath the ledge is carved away. Eventually, parts of the ledge may break off and the waterfall will move upstream. This process happens very slowly (over thousands of years) but it shows how water constantly reshapes the land.

Observable Features

When you visit Grand Falls, look closely at the surface of the rock. You will see cracks called joints, which formed as the rock was uplifted and weathered. These joints can make the rock easier to break apart. You might also see potholes, which are small round holes in the rock. These form when swirling water and gravel grind into the rock surface. Another feature is the layering between chert and thin beds of limestone. Sometimes, you will find fossils of ancient marine life in the limestone layers near the falls. All of these features help tell the story of how Grand Falls formed and continues to evolve.

A diagram showing how waterfalls retreat over time due to erosion

A Living Landscape

Grand Falls is not just a beautiful waterfall, it is a natural laboratory for understanding geology. By observing the rocks and their features, you can see how powerful forces like water and gravity shape the Earth’s surface. The chert ledge, the eroded channels, and the fossils hidden in the rocks all provide clues to a much older world, when this part of Missouri lay beneath an ancient sea.