Willamette River Sedimentation Earthcache EarthCache
Willamette River Sedimentation Earthcache
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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 is located on a downtown walk/bike trail along the eastern bank of the Willamete River.
Signage along trail gives the history and function of the river for the city of Portland. You will be fascinated by the historic information available in these panels!
Geology: Rivers are wild and are responsible for some of the grandest geologic movement on the planet. The Willamette River is a tributary of the Columbia River (to the North) and flows northward from Eugene thru Portland towards Vancouver before dumping into the Columbia. In Eugene is averages less than 20 feet deep, while in Portland its depth varies between 60 and 135 feet deep.
Several major geological events have shaped the Willamette River you see before you. First, the Willamette River was originally located east of Oregon City, but with the activity of the Boring volcanoes into the Quaternary period, the viscous lava transformed that region, rerouting the Willamette River to its present location, where it has cut its present gorge. Additionally, in ages past, the Clark River in Idaho and western Montana was blocked from draining by a huge ice lobe. The result was the fabled Lake Missoula . When that lobe finally released their flow, the Willamette Valley was flooded with hundreds of vertical feet water (up to 400 feet deep some geologists say) and sediment. Over time, the Willamette River began to re-establish its course through the area, cutting into the soft sedimented river bank.
As is the case with most sedimented river valleys, the river has wandered over the year, depositing sediments during flooding, rerouting itself as needed to continue its journey downstream. Prior to white man’s incursion into the area, this flooding simply shaped the landscape, providing fertile land, varied fishing, and the beauty of change. However, the great winter flood of 1861 destroyed several towns, including Linn City, Champoeg, and Scottsburg. The flood of 1894 seems to be the first flood well documented with photographs: one such famous picture depicts men thigh-deep in water in downtown Portland, pointing shotguns at decoy ducks as they float by in the flood waters. The great Vanport Flood of 1948 wiped Oregon's then second-largest city off the map. It was a WWII-era project city, built to temporarily house shipyard workers. The city stood near the confluence of the Willamette and Columbia Rivers, a spot later occupied by Portland International Raceway. Other notable floods include events in 1899, 1964, and the Willamette Valley Flood of 1996.
Since the 1920’s Portland has been growing rapidly, and one of its secrets to sustaining growth is the protection of its populace by the systematic taming of the Willamette River. In front of you, you can see the Portland Harbor Wall, extending from the Steel Bridge to the Hawthorne Bridge. This is 1920s urban renewal project, replacing rotting warehouses and cocks, reclaimed twenty city blocks. Designed as a dam to keep floods off the streets and out of the basements of businesses, the wall was also built to contain the first sewer system to catch west side waste.
Congrads to gracielouwho and ivhs72 on FTF (First to Finish logging requirements)!
Logging Requirements:
Send the answers to #1-#7 to me through my geocaching profile.
1. List the name “GC23BW6 Earthcache” in the first line of your email. Also, list the number of people in your group.
2. Estimate the distance across the river from the GZ. Based on the description above, What size/shape might the river have taken historically as it shaped this area?
3. Are there any evidences of sedimentation from the GZ? Why or Why not?
4. Examine the river area. What human-engineered structures can you see that have altered the geology (sedimentation, size, or direction) of the river?
5. From signage on the walk and the description above, what are the perceived advantages of the human shaping of the river? List at least two.
6. Complete the statement from signage posted at GZ: The ingeniously engineered structure is like an ________________________, with most of its mass ______________________________ ______________________. The fifty-one timber boxes supporting the concrete part of the mile-long wall can be seen only during very low water.
7. What date was this project dedicated?
I will only respond if you have incomplete logging requirements. Go ahead and log your cache
Resources:
USGS – Geology of Portland Oregon (visit link)
Wikipedia.org “Willamette River” (visit link)
Additional Hints
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