Thursday, October 23, 2014

Map 5: In Tight Places - Muddy Creek Access through Oakland Run Ravine

Sunday October 19, 2014: Muddy Creek Boat Access to Blair Road, State Gamelands 181

The morning started off cold and cloudy, with a chilly northwest wind driving down the river. We hadn't hiked long, however, before the sun started bursting through a lumpy, grey cloud deck. The wide fetch of the Susquehanna generated whitecaps and waves, but within the folds of the forested islands we were sheltered and warm. This Sunday's hike was all about the tight spaces from water gaps and canal locks to ravines and entrenched streams. Following last week's hike up Muddy Creek, one of the most beautiful river hill ravines in York County, Pennsylvania, this week's hike revealed many interpretations of tight places.

Restored lock on the Susquehanna and Tidewater Canal near Muddy Creek Boat Launch.

The interface of rock and river suited the building of the Susquehanna and Tidewater Canal perfectly. Constructed between 1836 and 1840, the not-so-wide canal accommodated the cigar-shaped cargo boats and not much more.  The canal company used immigrant labor gathered from the wharfs of Philadelphia, Wilmington, and New York.  Men and boys used picks, stone hammers, chisels, shovels, and wheel barrows to quarry nearby metaconglomerate schists from outcrops and borrow pits to build the narrow-walled locks, elevated towpath, bridge abutments, and lock houses. It was hard, dangerous work. While today not all the locks are restored (as was the first one we came across on this section) the dry stack stone walls and semi-watered ruins serve as important habitat for reptiles, amphibians, and insects. Come March some of the best vernal pool action around can be observed in the bottoms of these old locks and all manner of things from snakes to bats live in the generous cracks and crevices of the walls.

Loading a canal boat at the Peavine Island landing, now completely forested and reclaimed by nature. Credit - PPL.

The bridge over to Peavine Island (left). Credit - PPL.

The first third of our hike was out to the Bear Islands, an area recognized as containing some of the most biologically  diverse habitat of the entire river valley. Soft moss cushioned our steps and red and white pine trees whispered overhead in the wind. An immature black-crowned night heron lifted from her rocky perch at our approach.  Outcrops of uplifted rock carved and smoothed by thousands of years of glacial meltwater created a maze of kayak trails. Potholes, ledges, and beautifully sculpted cliffs provide places for miniature forests of pine saplings, bear oak, ferns, and grasses to grow, all sheltered from bitter winds and harsh sun. But occasionally floods waters will wash over the islands and scour the rocks clean of life, except for the deepest rooted plants.

Interface between bedrock and river - Bear Island Complex.

The idea that all life is transitory, changing, coming and going, is felt almost in-hand out here on the islands. Plant communities shift according to the seasons, and with the seasons come the responses of the river with its mean ice jams, violent floods, and deadly droughts. In summer there is unrelenting heat rising from the bare rock like from an oven and sometimes fire. Peavine Island shows evidence of an intense burn a few years back, where now pine saplings are sprouting, grasses grow, and fire-resistant trunks of the older trees still show. Except for those mature trees growing on the protected interiors of the largest islands, the edge communities seem to be all pioneer species, quick to anchor and grow and re-establish when disturbed.

Peavine Island overlooking a natural slough used by the canal boats.

There are some narrow spots along the Mason Dixon Trail in this eight mile section to be watchful for. Crossing a slim rim of rock, we rump-scooted down slick rock to drop hopefully to narrow ledges below.  We side-stepped along ledges too skinny on which to do otherwise. We peered into every pothole and pocket, and gawked at the broad shoulders of the islands over which hawks, vultures, herons, and eagles glided. From precarious cliff overlooks we watched the river course through the islands as it funneled into ancient channels, sometimes hundreds of feet deep. Strange swirling currents and cold upwellings of water signaled submerged potholes and great crevices below. 

Freshly fallen leaves made the downhill approach to Peavine Island a little slick!

White and red pine needles carpet the trails on Peavine.
Uplifted metaconglomerate bedrock showing the force of continental collision.

Peavine Island is worth a full day of exploring and is easily accessible by hiking in from the restored Lock 12 from the north, but the approach from the south might be tricky for children or older hikers. Be aware of high water which could block access from either end, and avoid going out when the dam is releasing following heavy rains and snow melt. Though sirens will sound from the Holtwood Dam a mile upriver, a distracted hiker or fisherman could get caught out there as waters rise and cover the rocky path. I love paddling through the Bear Island Complex, especially in the late fall and early winter before freeze-up but after all the poison ivy has died away! PPL monitors the islands and there are still folks who live out here in cabins, so take only pictures and leave only the groove of your kayak's keel when you leave.

Unrestored lock on Peavine Island.
A single remaining gate bumper log held in with iron spike nails.

Restored Lock 12.

The hydrologically connected landscape of flood cycles, alluvial soils, sediments, organic matter, and weathering bedrock make this area a rich biotic environment. There are rare and endangered plants here, rare turtles and amphibians, and large specimens of riparian trees like red maple, sycamore, and river birch.  I was a little annoyed with the Japanese knotweed that now shades out entire banks, however. It grows so thickly at the Muddy Creek Access that it blocks views of the river.

Swamp beggar tick flowers brighten a cloudy October morning.

Partridgeberry cascading over moss on Peavine Island.

Once off Peavine Island and heading north along the river the MDT follows the canal towpath and allows for some nice views of the river valley. The Norman Wood Bridge spans the island chain to connect York and Lancaster Counties. The clop-clopping of horses pulling buggies across the bridge high above made for some interesting acoustics as the trail crossed underneath the great piers and bridge deck. Again, narrow-goings as the trail teeters in some places on the rocky, eroded towpath until it veers suddenly up towards River Road and around an old mill foundation. In canal days, this path would have been a comfortable ten to fifteen feet wide, allowing a teams of horses or mules to walk along towing the canal boats.

The narrow two-laned Norman Wood Bridge (PA Rt. 372) connects York and Lancaster Counties.

From an interpretive panel showing the wide towpath (now trail) and horses pulling canal boat (PPL & Exelon sign).

Looking down into the wheel pit and axle housings for a long absent overshot wheel at a mill ruins.

The MDT began a beautiful climb up Mill Run, a favorite summer hike and the location of a nice swimming hole  for my grandkids. Mill Run tumbled and sang through its deep valley, one of two nice ravine creeks we would see today. Ravine ecosystems are unique to each creek and even though some ravines may only be a mile or less apart, each has its own special character and feel. But one constant is that north-facing slopes are covered in rhododendron woods, and south-facing slopes are covered in oak-hickory forest. I love hiking up the ravines in winter when the waterfalls and cascades are frozen and the noisy waters are silent.

North and south-facing slopes of a small side creek to Mill Run.

Mill Run on its sliver of a race to the Susquehanna River.

Our swimming hole in fall colors.

Unlike most creek valleys found here in the Piedmont, river hill ravines have  deep incised valleys, steep walls, and no floodplains. These can be dangerous places during flash floods, and sometimes the only way out is straight up. Though not flooding today, we climbed up and out of the Mill Run ravine on a series of pitched switchbacks, higher and higher, until we reached a narrow spine of rock that ran out to the edge of the ravine's valley wall.   The high ridge mirrored the deep valley in its steepness though an inverted V-shape, and while the trail continued along its apex we observed young  ironwood, hickory, and oak anchored in its thin rocky soils.Not until we dropped down below the ridge line did we start to see larger, mature trees growing in the richer soils, more protected from winds.

Ravine ridgeline, an inverted V.
Holtwood Dam built at a narrow gap in the river valley.

The wind was whipping the treetops about and from our resting ledge we could see whitecaps far below on Lake Aldred behind Holtwood Dam.  Unlike the C&O Canal along the Potomac which is still watered in many places (and great for flatwater canoeing!) the Susquehanna and Tidewater Canal has filled in with flood silts and sands or has been drowned by the ponds behind each of the three big dams that span the river at Conowingo, Holtwood, York Haven, and Safe Harbor. From the top we could see the height of water behind the dam and knew that our lock finding was over for the day.

A water gap carved out by the ancient Susquehanna. The Pinnacle is to the right - a popular hiking destination.

It seemed we were hiking either into or out of tight spaces all day long. We stopped to admire a water gap, a place in the mountain where the Susquehanna over millions of years has worked its way through the ridge, most likely following weakened joints or faults, while at the same time the mountain was being uplifted. Geologists suggest that the down-cutting was occurring at the same rate as uplift, producing the dramatic gaps we see now. The Susquehanna is famous for its many water gaps, some of which can be seen from heights such as the Pinnacle, a popular hiking destination on the Conestoga Trail opposite us (see pic above). The next ravine, Oakland Run, offered an up close look at down-cutting, faults, and entrenchment to the point of going almost underground.

Rugged outcrops within the Oakland Run ravine offer plenty of rock shelters.

The MDT follows the Oakland Run ravine for three miles to the top of the valley - and it is all up! This was some very rocky hiking, made a little slick by fallen leaves and overnight rainfall, followed by a mile-long trudge up a fire-break road to the top. For anyone who claims me to be a flatlander, here in Pennsylvania I dare them to follow the blue blazes through the river hills! Hiking poles strongly suggested and on this day greatly appreciated!

Oakland Run seems to dive underground at times, coursing through its ravine.

The metaconglomerate outcrops are high and very old. They were metamorphosed over eons from sea bottom sediments into sharply defined cliffs and walls of quartz, gneiss, and schists, eroded out of the hill by the steep descent and weathering action of the stream. An active regional fault bisects the ravine and it runs close to the surface here. Jumbled boulders, broken shelf rock, and torn gaps in the cliff walls are evidence of some powerful tremors in the past. Just north of the Pinnacle over in Lancaster County the fault line continues, running northeastward along the river. The Wind Caves, a popular set of angular passageways on the opposite shore are the result of the pushing and pulling of folded slabs of mile-deep rock as they rode over each other during continental collision. The cave is a fine example of a tectonic shifting and compared to limestone caves or lava tubes, it is the most rare of all cave types. 

The Pennsylvania Water and Power Company sign is a relic from the 1920s! (See Notes)

The colors and textures of the ravine are extraordinary this time of year. Of course, the colors have been there all along but with the shortening of days and dropping temperatures the colors of summer are dying away to reveal the colors of autumn. The wildness of this place was made all the moreso as the winds, still rushing overhead through the tops of hemlocks and white pines, was absent at trail level. We felt like in a world apart walking through time enveloped in a folder of investigations waiting to be opened by a future ecologist, mycologist, botanist, or geologist. I felt a little hurried as we kept up hiking pace to beat sunset, and would like to come back to just wallow in the different seasonal colors, scents, and sights. 

Hay-scented fern turns white with the first cold nights.

Like a time capsule, the Oakland Run ravine holds so many interesting discoveries about geological and botanical history that will take more time to uncover. It was fitting that the late day's golden light of mid-autumn filtering down through the yellows of hickory and beech resembled the golden hues of a morning in early spring. The seasonal glow reminds us that each year begins and ends with exaggerations of sunlight, magnified and dispersed through the slim skins of leaves, coming and going like a breath inhaled and exhaled over the span of a growing season. 

The ravine turns hard south then hard east, possible following a surface fault.


Though not a focus of this particular post, in reference to the old sign we found embedded in a hemlock trunk, this historical book on the Pennsylvania Water and Power company is archived online with the Internet Archive, a domain of the Creative Commons that links thousands of libraries around the world. Holtwood Dam was the first power-generating facility to link hydro and coal power, the first hybrid power plant in the world.

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