Report On Geology Report

1. What is the geological history of the Ohio River, and how does this history explain why the Ohio River gorge is so deep? (See Ohio Pleistocene History and Ray, 1974)
The geological history of the Ohio River started during the Pleistocene Epoch or the Ice Age. This period happened some 2 million years ago and ended 10000 years ago which then started the Holocene Epoch. The first documented deposits in Ohio were the glaciers of the Pleistocene. During the latter part of the Permian Era, erosion and non-deposition started and the entire Tertiary Period led to no record of preserved rock in Ohio. The sediments during the Pleistocene covered the southeastern third of the state and have been modified by erosion since melting of the last glacier. As the massive ice sheets melted, great volumes of melt water flowed in the river valleys. It carried with it large amounts of sediments. The Ohio River is commonly shallow but was falsely extended by a progression of dams. The dams bring the water level up in shallow extends, taking into consideration business route. Close to its starting point at the juncture of the Allegheny and Monongahela Rivers, the Ohio remains genuinely shallow, never transcending around 30 feet (nine meters) the distance past Cincinnati. From its beginning to Cincinnati, the normal profundity is roughly 27 feet (eight m). In any case, once past Cincinnati, the waterway extends generously. Because of the damming, alongside glacial mass developments and movements in the last piece of the second Ice Age, the stream's profundity increments almost fivefold over around 100 miles (161 km), going to a greatest profundity of 168 feet (51 m) only west of Louisville, Kentucky.
2. What are the various geological units (formations) at the site, and which is the dam founded on? Which units will need to support the foundations and abutments of the dam?
Some of the geological units in Ohio include the rich agricultural soils which formed two-thirds of the state. Waterways also formed in relation to ice sheets, including the Ohio River and the Lake Erie. These two bodies of water became avenues for transportation of products. Gravel, sand, clay, and peat also formed. Over 50 million tons of gravel and sand are generated through mining operations. Glacial clays are also present in Ohio and these clays are used to manufacture clay products. Lake Erie is one of the most important resources of Ohio which was developed as a direct result of the glaciers. The glacial grooves on Kelles Island in Lake Erie is built on certain geologic units such as boulders, cobbles, and pebbles.
3. What are the chief engineering properties and concerns (if any) related to the geological units and geomorphology (i.e., shape of the Earth’s surface) in the vicinity of the dam site?
Some of the chief engineering concerns at the site comprise of alluvial sands and rock overlain by better grained residues and dirt. The more profound, pervious sands and rock permitted the utilization of a generally separated profound dewatering great framework for overseeing groundwater on the site. Thickness of the overburden changed from 0 feet in the stream to as much as 60 feet thick ashore, still a few feet underneath the 100 year surge level the cofferdam was intended to ensure against. The highest point of bedrock was by and large found at about El. 558 as per the Ohio River Datum. The bedrock comprises of the Pennsylvanian Conemaugh Group, and comprises of a mixed bag of interblended sedimentary rock sorts, including sandstones, siltstones, shales, claystones, and indurated dirt with incidental limestone experienced amid the venture subsurface examinations. Rock stratigraphy was profoundly variable both vertically and on a level plane all through the site. Rock jointing was discovered to be for the most part low edge with differing plunge bearings. Proof of slickensides was experienced in a portion of the borings, especially in the better grained sedimentary rocks.
4. Visit the Ohioseis network web site and review historical earthquake epicenters in Ohio and Kentucky, and study the fault map of Ohio (included in the attached Google Earth kmz file). Is there any history or risk of seismicity in the area?
Even though a lot of people do not believe that Ohio is an earthquake prione area, there had been 200 earthquakes that happened in the area since 1776. A lot of these earthquakes have been felt merely locally and did not cause great injuries or damage. Seismic risk in Ohio as well as the eastern United States is hard to assess since earthquakes in general are infrequent compared to plate-margin places like California. In addition, active faults do not reach Ohio’s surface, and thus cannot be mapped in the absence of expensive subsurface methods. A great difficulty in knowing or projecting large earthquakes is that the recurrence interval or the time between massive earthquakes is very long, usually about hundreds or thousands of years. Earthquake is further compounded by the reality that seismic waves travel for long distances. The flat-lying and relatively brittle sedimentary rocks tend to carry the waves throughout areas of thousands of square miles for even an earthquake that is moderate in size. Another factor is the nature of geologic materials upon which a structure is built. Ground motion from seismic waves tends to be magnified by sediments including sand or clay and gravel.

Works Cited:

Hansen, Michael. “The Ice Age in Ohio.” Educational Leaflet No. 7. Revised Ed. (1997)