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“Bite-Size Bits of Local, National, and Global History”
“Bite-Size Bits of Local, National, and Global History”
Iowa City in Johnson County, Iowa — The American Midwest (Upper Plains)
 

View from the Overlook Plaza

 
 
View from the Overlook Plaza Marker image. Click for full size.
Photographed By Connor Olson, July 25, 2020
1. View from the Overlook Plaza Marker
Inscription.  The plaza area is located above the bend in the Devonian Fossil Gorge and affords views of both the limestone surfaces upstream and the developing wetland downstream. In the upstream direction, the 2008 flooding only slightly deepened of the gorge that was first cut into bedrock by the 1993 flooding. The more recent flooding widened the gorge, and it also removed the pile of unconsolidated ancient river sediments that appeared in the center of the gorge after the earlier flooding. The block of limestone that originally deflected the floodwater over this sediment mound was swept away in 2008. However, the newer flood exposed similar sediments further downstream.

The flooding of 2008 widened the downstream area of the gorge significantly, exposing old glacial till with an orange-red pāleosol (ancient soil).. Unfortunately the area was dangerously steep and had to be landscaped. It lies beneath the grassy hill that forms the West Bank at the lower end of the gorge. In this area, the rock of the gorge shows broad folds with numerous faults and fractures in the area of markers 15 and 16.

A great deal of rock material was

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deposited by the 2008 flood in the area just below the plaza. This material includes blocks of limestone ripped from the gorge floor and a large "raft” of concrete slabs connected with steel re-bar that once formed the plaza around the lower biostrome (marker 3) prior to the flooding. This material was deposited in the inside of the curve in the gorge, an area where the water's energy was dissipated.

Photo captions:
Left: View of Devonian Fossil Gorge looking upstream from the plaza as seen in the summer of 2010.
Right: View of Devonian Fossil Gorge looking downstream from the plaza as seen in the summer of 2010.

 
Topics. This historical marker is listed in these topic lists: DisastersWaterways & Vessels. A significant historical year for this entry is 2008.
 
Location. 41° 43.307′ N, 91° 31.939′ W. Marker is in Iowa City, Iowa, in Johnson County. Marker is on Riverwalk Trail south of Prairie de Chien Road Northeast, on the right when traveling south. Touch for map. Marker is in this post office area: Iowa City IA 52240, United States of America. Touch for directions.
 
Other nearby markers. At least 8 other markers are within 4 miles of this marker, measured as the crow flies. Site Geology (here, next to this marker); Devonian Fossils (a few steps from this marker); An Ancient Sea (a few steps from this marker); The Coralville Dam (a few steps from

View from the Overlook Plaza Marker image. Click for full size.
Photographed By Connor Olson, July 25, 2020
2. View from the Overlook Plaza Marker
this marker); Samuel Jordan Kirkwood (approx. 3.8 miles away); Old Brick (approx. 4 miles away); Mormon Handcart Brigade Camp (approx. 4.1 miles away); St. Mary's Church (approx. 4.1 miles away). Touch for a list and map of all markers in Iowa City.
 
Devonian Fossil Gorge image. Click for full size.
Photographed By Connor Olson, July 25, 2020
3. Devonian Fossil Gorge
 
 
Credits. This page was last revised on March 9, 2021. It was originally submitted on March 9, 2021, by Connor Olson of Kewaskum, Wisconsin. This page has been viewed 130 times since then and 5 times this year. Photos:   1, 2, 3. submitted on March 9, 2021, by Connor Olson of Kewaskum, Wisconsin. • Mark Hilton was the editor who published this page.

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Apr. 16, 2024