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Losing Battle of Water and Land EarthCache

Hidden : 05/15/2007
2 out of 5
2 out of 5

Size: Size:   not chosen (not chosen)

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Geocache Description:

Here you will find that Elk Falls Park has tons of things for you and your family to do. From hiking six miles around the park to going to the falls and even fishing or swimming you will find tons of activities to do here while looking for an earth cache.

Waterfall Formation

Three main processes create waterfalls:

* Recent uplift or down-dropping of part of the Earth's crust;
* Diversion of a river by blockage of a preexisting channel; or
* Differential erosion of valleys, especially in glaciated areas.

In all cases, where a major river plunges over a waterfall, geological processes must have been active within the past few million years. Rarely are large waterfalls older than a few tens of millions of years, and most are less than a million years old. Invariably the rock at the crest of the falls is one of the harder varieties, resisting the downcutting effects of the river.

Waterfall Erosion

The pounding of the water at the base of a waterfall is a powerful force for erosion, especially if the water contains suspended sediment. Even at the lip of the fall, the water gains extra erosive power as it accelerates approaching the brink. For this reason, waterfalls are temporary phenomena, geologically speaking. While the surging water tears away at the base of the falls, removing its rock foundations, the scouring of the lip grinds back the brink of the falls, decreasing the overall height. In some cases, the removal of the underlying rock leads to a collapse of the lip itself.

The time it takes for these processes to erode the river bed to a gentle slope depends on the volume of water flowing over the drop, the amount of sediment available to grind away the bed, and the hardness of the rock over which the river flows. Even waterfalls on smaller rivers can last for millions of years. This is also true of large rivers where the bedrock is resistant to erosion. But in geologic terms, waterfalls are quite temporary, and their presence is a sure sign of the special geologic conditions that produced them. In a sense, they are like the flip side of lakes, which are also temporary, mostly because lakes gradually fill with sediment and eventually turn into marsh and meadow.

To claim credit for this cache:

1. Post a picture of you and your GPS at the falls.

or answer the following:

2. Measure or estimate how much (in feet and/or inches) the waterfall has cut into the rock and how much erosion of the mountain has this fall taken from the earth?

3. What mountain chain is the fall a part of?

Additional Hints (No hints available.)