Department of the Interior, U.S. Geological Survey
Henry Gannett, Chief Topographer
Surveyed 1890, Edition of Oct. 1899, reprinted 1937.
Scale: 1 : 62500
Hello everyone,
I hope everyone is enjoying the great weather! This week, I would like to present this relief map that shows the topography of Harrisburg, Pennsylvania. I’ve always been interested in the three-dimensional representation of the terrain on relief maps. This topographical map of Harrisburg is one of the many relief maps we have in our collection.
As shown on the map, the city of Harrisburg sits south of Blue Mountain, adjacent to the Susquehanna River. However, the most noticeable feature on this Harrisburg relief map is probably the northeast-southwest-oriented mountain ridges. The paralleling mountain ranges–including the Blue Mountain, Second Mountain, Third Mountain, and Peters Mountain–are the Appalachian Mountains that formed during the continental collisions in the assembly of the supercontinent Pangea. These mountain ridges belong to the Ridge and Valley Physiographic Province. The compression of continental collisions deforms the rock, forming the folded strata with anticlines and synclines. While more resistant rocks form the ridges, the rocks that are more susceptible to erosion–like limestones and shales–make up the valleys.
Besides the mountain, the Susquehanna River that cuts through the ridges is also interesting. Some believe that Susquehanna is an ancient river system that existed even before the Last Glacial Maximum. On this relief map, one can really see the erosive power of the water!
Have a wonderful week！
Yidan Xu ’24
