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THE COUNTY’S NATURAL ENVIRONMENT
PLANNING ISSUE
Local geology conditions
determine development site
suitability, cost of construction,
and potential for local
hazards such as sinkholes.
Mining and gas drilling
opportunities are also shaped
by local geology.
What’s New
•
The six large active quarries in Montgomery County
are located in Whitemarsh, Upper Merion,
Montgomery, Marlborough, Lower Salford, and
Lower Pottsgrove Townships.
•
Two large quarries in East Norriton and Plymouth
Townships have closed since 2000. The county has
several former quarries which are currently being
filled in accordance with their reclamation plans or
reused for other purposes. One large former quarry in
Upper Merion Township serves as a major water
supply source.
•
There is natural gas potential in the South Newark
Basin which covers the western portion of the county,
though a moratorium exists on drilling in the South
Newark Basin until 2018.
•
Even without local gas development, Montgomery
County could see changes due to gas extraction
occurring elsewhere in the state. These changes could
involve new gas pipelines, gas processing facilities,
and other industry linked to natural gas.
Geology
Climate
Hydrology
Floodplains
Air Quality
Steep Slopes
Soils
Wetlands
Woodlands
Wildlife
Natural Areas Inventory
Geology
Geology is the science and study of the solid matter of the
earth, its composition, structure, physical properties, history
and processes that have shaped it since the planet’s
formation. Understanding geology is essential since the local
bedrock forms the foundation for the county and greatly
shapes its natural resources. In combination with the local
climate, geological characteristics of the rock, both physical
and chemical, influence hydrologic and terrestrial features
such as local soils, wetlands, surface and ground water,
vegetation, and topography. Subsequently, their
characteristics may impact woodlands and wildlife. In order
to understand the county’s natural resources one must
understand its geology.
The border between two major geologic areas crosses the
county along a northeast-southwest line extending from
Willow Grove in Upper Moreland Township to King of
Prussia in Upper Merion Township, with the Triassic
Lowlands falling to the north and the Piedmont Upland to
the south. The Piedmont Upland is comprised of older
metamorphic and igneous rock (granite and schist), although
there is a band of carbonate rock that stretches east from
Chester County to Abington Township. Wissahickon Schist/
Granitic Gneiss/Hornblende Gneiss, Chickies Quartzite, and
Ledger Dolomite/Elbrook/Conestoga Limestone, are the
formations found in the Piedmont Upland. The younger
rocks that characterize the Triassic Lowlands are primarily
red shales and sandstones, with intrusions of diabase. Four
formations: the Stockton Sandstone/Conglomerate/Shale,
Lockatong Argillite/Shale, Brunswick Shale/Sandstone, and
diabase, make up the Triassic Lowlands. The Triassic rocks
are exposed in northeast-trending belts which broadly
undulate and are faulted in various locations.
Local bedrock is still mined and quarried in the county. At
one time quarries were established in nearly every geologic
formation though most existed along the limestone and
dolomite formation that parallels the Pennsylvania Turnpike.
High-grade calcium aggregate from these quarries was used
by the steel industry and for building construction. Other
limestone from these quarries was crushed and used as
concrete aggregate, roadway base or railroad aggregate.
