Marshall County, Kentucky

 

GEOLOGIC HAZARDS

 

There are several shallow, concealed, and exposed faults located throughout Marshall County. Currently there is no evidence suggesting these faults are active. However, because of the proximity of Marshall County to the New Madrid Seismic Zone strong earthquake activity is a possibility. Soil creep, slumps, and landslides along steep slopes may occur from erosion or ground motion associated with a strong earthquake. Areas associated with alluvium material are subject to liquefaction during a strong earthquake. These areas are also subject to flooding. Soils derived from alluvium deposits have a moderate to high shrink-swell capacity that may affect structural foundations and roads. Flood information is available from the Kentucky Division of Water, Flood Plain Management Branch, www.water.ky.gov/floods/.  

 

  Surficial materials in  Marshall County are unconsolidated and generally saturated with water, which can make these materials   prone to collapse during excavation. Shallow excavation through these surficial materials is needed in order to construct water and sewage pipelines. Photo by Glynn Beck, Kentucky Geological Survey.

 

 

  Parts of Marshall County are prone to flooding; this bridge crosses Cypress Creek in the northern part of the county. Photo by Glynn Beck, Kentucky Geological Survey.

 

 

  The 60-year-old Kentucky Dam, constructed by the Tennessee Valley Authority on the Tennessee River, is 206 feet high and 8,422 feet long. Kentucky Dam forms Kentucky Lake, and provides flood protection to millions of acres on the lower Ohio and Mississippi Rivers. Kentucky Dam also produces hydroelectric power, with a generating capacity of 184,000 kilowatts. Photo by Glynn Beck, Kentucky Geological Survey.

 

 

EARTHQUAKE HAZARDS

 

Peak ground acceleration at the top of rock that will probably occur in the next 500 years in Kentucky

Although we do not know when and where the next major earthquake will occur, we do know that an earthquake will cause damage. Severity depends on many factors, such as earthquake magnitude, the distance from the epicenter, and local geology. Information on earthquake effects is obtained by monitoring earthquakes and performing research. Such information is vital for earthquake hazard mitigation and risk reduction.

 

The most important information for seismic-hazard mitigation and risk reduction is ground-motion hazard. One way of predicting ground-motion hazard is by determining the peak ground acceleration (PGA) that may occur in a particular timeframe. The map above shows the PGA at the top of bedrock that will likely occur within the next 500 years in Kentucky (Street and others, 1996). It shows, as expected, that PGA would be greatest in far western Kentucky near the New Madrid Seismic Zone. Ground-motion hazard maps for the central United States and other areas are available from the U.S. Geological Survey. These maps are used to set general policies on mitigating damage. For example, maps produced by the USGS in 1996 were used to determine seismic design in building codes. For additional information pertaining to earthquake hazards visit the Kentucky Geological Survey website at www.uky.edu/KGS/geologichazards/geologichazards.html

 

 

GROUNDWATER

 

Groundwater resources in Marshall County are abundant and have fair to good water quality. All areas of the county can produce water from drilled wells at reasonable depths in quantities sufficient for domestic use. Multiple zones of production are common throughout the county. The depth to uppermost production is between 30 and 150 feet.  A few wells may intersect shallow perched water from gravel or alluvial deposits, but these zones often will not yield sufficient water for an adequate domestic supply during periods of low rainfall, which is typical in late summer and fall. Water from alluvium and limestone in this county is generally hard to very hard, with moderate to high levels of dissolved solids. Some limestone wells in the eastern part of the county contain minor amounts of hydrogen sulfide. Water from the unconsolidated sand or gravel aquifers is considered soft and slightly acidic, with low dissolved solids. Water quality generally is good except in areas where downward percolation of surface water and fluids from domestic sewage-disposal systems and other sources of domestic or industrial pollution have contaminated the aquifer. In a few wells, harmful amounts of nitrate have been detected. Groundwater sometimes contains naturally occurring iron and manganese in objectionable amounts from the deeper zones. In some formations with slightly acidic groundwater, a chemical reaction between the acidic groundwater, steel well casing, and pump equipment will produce a high iron content. For more information about groundwater in the county, see Carey and Stickney (2001).

 

 

 

THE LAND

 

 

Clarks River National Wildlife Refuge comprises  over 7,000 acres and is the only National Wildlife Refuge located completely within the state of Kentucky. The refuge begins just southeast of Benton and extends nearly to Paducah; the majority of the refuge lies within Marshall County. Photo by Glynn Beck, Kentucky Geological Survey.

 

 

  Many manufacturing companies have located in the Calvert City Industrial Complex because of the excellent transportation routes (Ohio and Tennessee Rivers and railroad and Interstate access) and the inexpensive hydroelectric power produced by Kentucky Dam. Photo by Glynn Beck, Kentucky Geological Survey.