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Limestone Valley


The Limestone Valley, also called the Cement Belt, is located at the southern half of the Lehigh Valley to the base of South Mountain. It is very flat in elevation, ranging from 200 - 500 feet above sea level.

The main types of rock are sedimentary rocks (limestone) and about 505 - 570 million years old (Cambrian).

Limestone is formed by the deposition of shells and other marine invertebrates on the ocean floor! Today farmers use limestone powder to neutralize soil pH.

The Jacksonburg formation is the most notable formation in the Limestone Valley. The Jacksonburg Formation, a narrow belt that runs along the northern border of the Limestone Valley, is best known for producing a type of limestone that is good for making cement.

Cement is an important part of Lehigh Valley's past. It was discovered that the Jacksonburg Formation contained the right material to easily make cement. In 1871, American Portland Cement was first made in the Lehigh Valley by Coplay Cement Co and today the Lehigh Valley is the largest cement producing region in Pennsylvania. The Atlas Cement Company of Northampton had over 5000 employees when they were involved in the Panama Canal project. They were also involved with the building of the Empire State Building, Rockefeller Center, and the Holland Tunnel.

Sinkholes have been known to occur in the southern Lehigh Valley due to lots of limestone in the bedrock. Limestone is easily dissolved by carbon dioxide (the gas that you breathe out) when it is mixed with water. Because of the carbon dioxide gas in the air, it mixes with water when it rains. As the mixture (carbonic acid) seeps into the limestone, the limestone slowly erodes away. It is a lot like slowly adding drops of water to a clump of sugar. Eventually the water will dissolve the sugar completely. The same thing happens to the limestone. The carbonic acid dissolves the limestone that is under the ground, causing a hole to form. Eventually the land over the hole collapses and takes cars, houses and roads with it!

Go to Educational Materials to download information about sinkholes!


Geologic Time Scale | What is Geology? | Exploringthe Lehigh Valley | Rock on! Educational Material

Pennsylvania Geology | Which Way is North? | Geologic Explorations | Dino Inquiry | Wonderful World of Rocks and Minerals

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