Geology and history recorded in Susquehanna rocks
Overlooks tell its sweeping story
Jeri Jones stood on a hill a couple of hundred feet above the Susquehanna River and explained how, at one time, he would have been underwater at this very spot.
“Imagine the river was at least as high as those hills that you see right there,” he said, pointing to hills across the river that overshadowed Safe Harbor Dam and rose above the hill where he stood in Apollo County Park. “So 125 feet above our heads is where the river would have been at some stage at the end of the ice age,” said Jones, a geologist and program coordinator with the York County Department of Parks and Recreation who has given many talks about the river’s geological history.
“That is what made the Susquehanna, really, what it is today.”
And what it is today here, and at many vantage points along the lower portion of the river, is spectacular.
Overlooks from the remnants of ancient mountains offer sweeping vistas of a river that — in one form or another — has been passing along the same route for hundreds of millions of years — though perhaps not always flowing in the same direction.
There are nearly pristine valleys, rocky gorges, views of small river towns tucked along the banks and dams that shape much of the river’s appearance today, as well as forests and farms.
Humans are not the only ones who appreciate the setting. As Jones spoke, a bald eagle swept past. The forested hillsides, often interspersed with rock outcrops, give eagles a great view for plucking fish out of the water below, and their numbers along the river have grown steadily.
“I think it’s one of the unsung attractions of the river,” said Mark Platts, president of the Susquehanna Gateway Heritage Area. “People know the views are nice, but you could actually make a day of it — or more.”
His organization is working to package the vistas — which are managed by an array of entities — so visitors can more easily find them.
Today, the river is part of the Captain John Smith Chesapeake National Historic Trail. Smith was the first European to look at the East Coast’s largest river during his 1608 explorations. But unlike his thorough exploration of the Bay’s tidal tributaries farther south, Smith never made it far up the Susquehanna. “Though canoes may go a day’s journey or two up it, we could not get two miles up it with our boat for rocks,” he wrote.
Rocks historically were a defining feature of the lower Susquehanna, especially in the section from Columbia, PA, to Perryville, MD, which is known as the Susquehanna Gorge. The rocks here were harder to cut through and the river, which is 1.5 miles wide in some places, is squeezed to a quarter mile in others. The river also drops sharply in this area — roughly 6 feet per mile — which made it attractive for the construction of a series of hydroelectric dams.
Those dams hid the river’s rocky bottom, but also preserve undeveloped lands around their reservoirs, thereby protecting spectacular views — albeit of an altered river.
People who make the 1.5-mile hike to the Turkey Hill overlook can get a glimpse of the changes. There, they’ll find a reproduction of a watercolor painted by Benjamin Latrobe that shows the scene as he saw it in 1801. Visitors can also get a sense of how the Susquehanna once looked below the Holtwood Dam by following the Mason-Dixon hiking trail south of historic Lock 12 to Lock 13, where some uncovered rock islands remain. The locks are remnants of the old Susquehanna and Tidewater Canal that once helped boats bypass these rock obstacles.
But the human impact on the Susquehanna — though substantial — is dwarfed by the acts of nature (and plate tectonics) over the millennia.
Much of the land that forms the area was once under the ocean, and began rising several hundreds of millions years ago. The ancestral Susquehanna began forming as the land rose above the ocean, though it likely flowed north at that time. Geologists believe an arc of volcanoes crashed into the area, roughly along a line from Baltimore to Newark, DE, around 450 million years ago. They would have blocked any drainage to the south.
About 350 million years ago, all of the continents floated together, forming the Pangea supercontinent. Africa collided with the East Coast of North America, folding the Earth’s crust to create mountains as high as the Rockies or the Alps today.
The Susquehanna, its bed already formed, cut through the ancestral Appalachian Mountains as they rose around the waterway. At some point, the river teeter-tottered and began flowing south along its already established riverbed. “It was just more or less like having a gutter and me tilting the board,” Jones said. “The water is going to follow that same pattern, just in the opposite direction.”
Over tens of millions of years, wind and rain whittled away miles of mountain rock and soil, washing it toward the ocean where it became the continental shelf and formed the flat Coastal Plain between the Piedmont and the Atlantic.
The final major act in the formation of today’s landscape came during the ice ages, which began about 300,000 years ago and ended around 10,000 years ago. Mile-high ice sheets covered much of the upper Susquehanna watershed.
As the glaciers melted, they sent massive amounts of water and eroded sediment downstream. The flows were spectacular — the river was hundreds of feet deep, flooding far up the valleys which intersect it. Rocks and sandstone formations left from the Susquehanna during the ice ages are found far up these valleys today.
When the last ice age ended, enough rich Pennsylvania soil was deposited downstream to create the Delmarva Peninsula, and the eastern shore of the then-forming Chesapeake Bay. (Somewhat ironically, Marylanders today tend to complain about this sediment transport.)
Geologically speaking, the present is a peaceful time. The rate of erosion is about equal to the rate that the Earth’s crust is rising in the area. “We have a neutral landscape right now,” Jones said.
“A million years from now, it could be different,” he added. “It probably will be different.”
In the meantime, it’s a great time to visit an overlook, and take a fresh view of one of the world’s oldest rivers.
Overlooks on the Lower Susquehanna River
Here is a selection of Lower Susquehanna views that are accessible to the public. Some are easy strolls to overlooks, some more strenuous hikes up hills. Find details and directions though a web search of the park or site’s name.
- Chickies Rock County Park is located midway between Marietta and Columbia in Lancaster County off PA Route 441, just north of U.S. Route 30. A half-mile hike takes visitors to the top of Chickies Rock, a quartzite outcropping towering 100 feet above the river with numerous views. The Breezyview Overlook, located about a half-mile south of the Chickies Rock trailhead on Route 441, also offers a good overlook, with no hiking required.
- Highpoint Scenic Vista & Recreation Area, located just south of Wrightsville, PA, on Hills Road is a high, grassy knob. A short half-mile walk rewards visitors with a 360-degree view that includes excellent vantages of the river to the north and south.
- Turkey Hill, which is managed by the Lancaster Conservancy, is reached after a 1.5-mile forested hike, which includes the largest pawpaw trees north of the 39th latitude, to spectacular views of the river. It shares a trailhead with the Enola Low Grade Rail Trail, which is found by taking River Road about 1.5 miles south of Washington Boro.
- Urey Overlook, located on PA Route 425 in York County between Kline Road and the Otter Creek Campground, offers a sweeping view of the river after a short hike along a portion of the Mason-Dixon Trail.
- House Rock Overlook, which is managed by the Lancaster Conservancy, is reached after a hike of about a third of a mile, where visitors are rewarded with a magnificent vista of unspoiled river gorge between Safe Harbor and Holtwood dams, near Pequea.
- Pinnacle Overlook, in Lancaster County, offers a majestic view of Lake Aldred, created by nearby Holtwood Dam, which is just out of sight. The overlook is easily accessible and found by taking River Road north from PA Route 372, and turning west onto Pinnacle Road, which takes visitors to a parking area a few hundred feet from the overlook.
- Lock 12 Historic Area, located on the west bank of the Susquehanna River off PA Route 372, isn’t a hilltop overlook, but adventurous hikers can walk south on the Mason-Dixon Trail under the Route 372 bridge toward Lock 13, where they can scamper over to rocky islands and get a sense of what the Susquehanna Gorge looked like before the dams were built.
- Susquehannock State Park, located in Lancaster County just south of PA Route 372 along the river, offers two scenic views along its Overlook Trail. The Hawk Point Overlook offers a view to the south of the top end of the Conowingo Reservoir. The view at Wisslers Run Overlook is a natural, rocky riverbed in the stretch of river below Holtwood Dam.
- Apollo County Park is reached from PA Route 425 by going east on Shenks Ferry Road a short distance to the parking lot on the left. Follow Trail “2” until it meets the blue-blazed Mason-Dixon Trail and follow it east, crossing Boyds Run and generally going uphill to a power line opening that offers a nice view of the river. The rugged topography around Boyd’s Run offers an excellent example of the erosive power of a small stream over time.
- Samuel S. Lewis State Park has 885-foot Mount Pisgah, the highest point in the area. Located about 2 miles west of Wrightsville, PA, it’s farther from the river than the others on the list, but it offers panoramic views of the Susquehanna River valley and the surrounding countryside.
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