Pennsylvania Highlands Geology

The Pennsylvania Highlands are the foothills of the Appalachian Mountains. The irregular ridges and deep valleys of this unique landscape feature common themes that reflect the region’s geology, which has influenced local history and land use. Much of the Pennsylvania Highlands are comprised of the Reading Prong Geologic Formation. The Reading Prong is found primarily in Berks, Bucks, Montgomery, and Northampton Counties.

Two types of rock are common to the erosion resistant, largely forested ridges of the Pennsylvania Highlands: diabase (basalt), and granitic gneiss and quartzite (see map). The diabase areas create natural limitations for agriculture and land development, due to the size and abundance of boulders. As a result, these areas feature large contiguous woodlands such as Hopewell Big Woods and Unami Hills.

The high iron content in the gneiss and quartzite rock ridges provided the raw material for the region’s industrial legacy of iron and steel. This legacy is reflected in the names of towns, historic sites and parks found throughout all thirteen counties of the Pennsylvania Highlands region: places such as Durham Furnace, Coventry Forge, Hopewell Furnace, Johanna Furnace, Cornwall Furnace, and Pine Forge Furnace. The desire for a recreation resource to connect these historic areas and unique natural resources was the impetus for development of the Highlands Trail in Pennsylvania. The unique combination of forests, rocky hills, historic sites, industrial towns, and fertile limestone valleys makes for a compelling story told through interpretive signage and online tools, enhancing the experience of trail users.

Diabase boulders along the Unami Creek, Montgomery County

News

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Great American Outdoors Act signed into Law

On August 4th, 2020 GAOA was enacted into law! This measure provides full, permanent dedicated funding for the Land and Water Conservation Fund and a $5.9B investment over 5 years to address the maintenance backlog on public lands. Read More

Recorded Webinar: "Discover the Highlands Trail in Pennsylvania"

Watch the webinar from early August 2020 hosted by the PA Highlands Coalition, which featured Appalachian Mountain Club staff Patricia McCloskey and Catherine Poppenwimer. Read More

US House Passes GAOA, and it moves to the President's Desk

On July 22, 2020 the US House of Representatives passed the Great American Outdoors Act (GAOA) by a wide bi-partisan margin, 301-107! Read More

14 Acres Added to Nockamixon S.P. in the PA Highlands

On July 9th, 2020 Natural Lands announced the completion of a 2-parcel land acquisition project using federal Highlands funding in Bucks County, PA. Read More