The rim of the caldera has been worked upon, worn back and eroded by many of the tools of nature. Melting snows in the early summer carry into the lake a vast amount of material. Sliding snow undoubtedly has its effect in the winter time. The prying force of ice - the sand blast of wind - all of these things perform a never ending task the result of which (a few geologic hours away) wear down the Rim. Of course, we will never live to see that time, or will or progeny. But Nature, may I put in a word for two great workhorses: the Crater Lake Ground Squirrel, and his cousin the chipmunk.

The observant person standing on the Rim will note that fifteen minutes is a long period between rolling boulders. He will also note that boulder slides do not start by chance - that behind it all is some perniceous rodent.

Mr. Ground Squirrel's technique is perfect. A small rolling pebble and he scores a ten strike against one a little larger. Down the wall the material goes until a landslide is the result of the first pebble.

Some ambitious student might calculate the tonnage and volume of rock entering the lake daily in this fashion and calculate how many millions of years it will take the chipmunk clan to destroy the West Rim.