Heavy rocks float? That's erratic!
Size:  (not chosen)
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Congrats to JenBut who was FTF!!!!
As an earthcache, there is no “box” or “container” to discover. Rather, with this cache, you discover something about the geology of the area. For more info, consult www.earthcache.org
This earthcache has been placed with the permission of the University of Oregon Natural History Museum. If you have time, please stop in the museum and view the impressive collection of local fossils and other displays.
Near the front doors of the museum is a plain looking stone. This stone is no ordinary stone; it is an ‘erratic’. If you were standing in this same spot some 12,000 years ago you might have been under 300 feet of torrential water. The water and this Montana rock were brought here during massive ice age floods. The forces that deposited this rock on the Willamette Valley are the same forces that gouged out the Columbia River Gorge and created the Channeled Scablands. To learn more about the Ice Age floods, please visit the Ice Age Floods Institute website at (visit link)
This plain looking boulder represents Oregon’s Ice Age past. It is not from the Willamette Valley or even from Oregon. Humans or animals did not transport it to the Willamette Valley. What could move this rock, known as an erratic, to the Willamette Valley?
About 12,000 years ago, during the last ice age, there were huge glaciers just a few hundred miles northeast of Eugene, in what is now western Montana. These glaciers dammed lakes, creating enormous lakes. One huge lake, called Lake Missoula, formed behind a half-mile high wall of ice. It covered over 3,000 square miles of western Montana and held 500,000 cubic miles of water. When the ice dam could no longer hold Lake Missoula, it burst and emptied the entire lake in a 48 hour time period. The Missoula Floods filled the southern end of the Willamette Valley with some 200-300 feet of water before it drained out to the Pacific through the Columbia Gorge.
How did this rock make it so far south in the Willamette Valley, you ask? These rocks were part of the glaciers and ice dams. They were stuck in the great sheets of ice and when the ice dam broke, sending 400-foot high walls of water down the Columbia Gorge, the rocks were stuck in the ice and floated and washed downstream. This rock was actually found in nearby Harrisburg and now has a home at the University of Oregon’s Museum of Natural History.
To claim this cache you must complete 2 different tasks:
1) Email the cache owner with the following information: (do NOT post on the website)
a. Measure the circumference of the rock. This can be done a non-standard unit of measurement.
b. Find the petrified wood and decide if the petrified wood or erratic rock has larger circumference.
c. Walk the brief stone path that is this garden (about 100 feet long). This path is the museum’s model of the earth’s era timeline. It does not break down the eras into periods or epochs, but it does show a representative distance between each era demonstrating how long each era lasted. This is a walking timeline using basalt columns with the era name etched into the stone. Look at the last era shown: what is the PHYSICAL distance between the two stone columns representing the last two eras?
2) OPTIONAL: If you can, it is optional to post a photograph of yourself in front of the erratic rock or the Willamette Meteorite replica.
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