Landforms in Carbonate Areas

Karst topography is a landscape form created by the dissolution of layers of soluble carbonate bedrock such as limestone or dolomite and results in unusual subsurface drainage.  Many carbonate areas in PA display one or more of the following distinctive surface and subsurface features :

  • sinkholes

  • closed depressions

  • vertical shafts

  • disappearing streams 

  • springs

Groundwater Contamination

Groundwater in karst areas is as easily polluted as surface water.  Overloaded or malfunctioning septic systems in these areas may allow sewage to flow directly into underground channels or caverns. 

Dissolving limestone produces conditions that can lead to:

  • extremely high permeability rates 

  • reduced opportunities for contaminants to be treated

As a result of  waters bypassing naturally- filtering non-carbonate soil and rock, water supplies in carbonate regions may become unsafe.  

Contamination also occurs when sinkholes are used as trash dumps.

Weathering and Erosion of Carbonate

Weathering in a carbonate area may result in a variety of large or small-scale features both on the surface and subsurface. Beneath the surface, complex underground drainage systems and extensive caves and cavern systems may form.

The need for care when dealing with carbonate soils and bedrock is clear.  Sinkholes can develop gradually as surface openings enlarge, but often erosion is unseen until the roof of an underground cavern suddenly collapses.  Such events have swallowed homes, cars, and even highways, as on PA Rte. 33 in Nazareth in 2004.

Penn's Trail Investigations

Penn’s Trail conducts a combination site inspection and subsurface investigation by a Professional Geologist who will:

  • correlate published mapping with current surface and subsurface indicators

  • use remote sensing techniques for parcels located within or adjacent to mapped carbonate bedrock

  • evaluate sites for indicators of carbonate weathering 

  • provide verification of either the presence or absence of carbonate bedrock

  • issue a report of methodology

  • make recommendations for further testing if necessary.

Our investigations are performed to ensure your project will comply with all municipal or state land development requirements.

No method to accurately predict future carbonate feature development has been developed to date.  Our work and subsequent reporting cannot guarantee future behavior of the carbonate bedrock or its overburden.  Recommendations and opinions are based on information gathered at the time of the site evaluation and are subject to revision as new information becomes available.

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