TRAIL OF GEOLOGY by fuv20424

VIEWS: 43 PAGES: 15

									                                              PARK GUIDE 4
                                                      2003




Pennsylvania

TRAIL OF GEOLOGY



             Moraine and
            McConnells Mill
             State Parks
           Butler and Lawrence
                 Counties



                         Glacial Lakes and
                         Drainage Changes




           Commonwealth of Pennsylvania
           Department of Conservation and Natural Resources
           Bureau of Topographic and Geologic Survey and
           Bureau of State Parks
When reproducing material from this book, please cite the source as follows:
  Fleeger, G. M., Bushnell, K. O., and Watson, D. W., 2003, Moraine and Mc-
  Connells Mill State Parks, Butler and Lawrence Counties—Glacial lakes and
  drainage changes: Pennsylvania Geological Survey, 4th ser., Park Guide 4,
  12 p.

                   Pennsylvania web site: www.state.pa.us
             Department of Conservation and Natural Resources
                      web site: www.dcnr.state.pa.us
                Bureau of Topographic and Geologic Survey
                  web site: www.dcnr.state.pa.us/topogeo




                   Drafted by James H. Dolimpio




             COMMONWEALTH OF PENNSYLVANIA
                      Edward G. Rendell, Governor
                  DEPARTMENT OF
        CONSERVATION AND NATURAL RESOURCES
                     Michael DiBerardinis, Secretary
   BUREAU OF TOPOGRAPHIC AND GEOLOGIC SURVEY
                     Jay B. Parrish, State Geologist
                    BUREAU OF STATE PARKS
                          Roger Fickes, Director
               Moraine and McConnells Mill
                       State Parks
                               by
                         1
    Gary M. Fleeger, Kent O. Bushnell,2 and Donald W. Watson2

Visitors to Moraine and McConnells Mill State Parks see completely different
scenes and attractions. McConnells Mill has a scenic gorge, waterfalls, rugged
hiking trails, a whitewater stream, and a historic grist mill. Moraine has a
large lake where visitors may go fishing, boating, or swimming, and a gentle
bicycle trail. And yet this variety obscures a common geologic foundation
and a similar geologic history. How and why two parks that look so differ-
ent have similar, or related, geologic histories is the story of this park guide,
which was originally published as two separate guides (PG 4 and PG 9).
Both parks share the same bedrock formations, and both gained their to-
pography from the same glacial events. The bedrock formed 300 million
years ago from layers of sand, mud, and peat. The topography was formed
mainly during the Ice Age (approximately 2 million years ago to 23,000
years ago) as rivers diverted by the glaciers cut new channels into the land.
Moraine State Park is named for the ground and end moraines deposited
by the glaciers. It is somewhat of a misnomer. Little morainal topography
exists within Moraine State Park because little of the park was ever covered
by glaciers.


How to Use This Guide
The information in this booklet is organized in this way:
    *How the bedrock in the parks formed and the mineral resources that
      impacted the region—pages 2–3.
    *Glacial lakes and the formation of Slippery Rock Gorge—pages 4–5.
    *Geologic map showing the locations of features and sites of interest
      described in the text—pages 6–7.
    *Descriptions of specific geologic sites of interest—pages 8–13.
          Look for this symbol in the guide and a similar signpost at each
          site to match descriptions and locations.
1
  Pennsylvania Department of Conservation and Natural Resources, Bureau of Topographic
  and Geologic Survey, 3240 Schoolhouse Road, Middletown, PA 17057–3534.
2
  Department of Geography, Geology, and the Environment, Slippery Rock University, Slippery
  Rock, PA 16057–1326 (Professor Emeritus).




                                            1
                              Bedrock                     large ripples and dunes. Extensive
                                                          swamps formed on the river flood-
The cross section below shows most                        plains and behind the beaches. In
of the visible bedrock in McConnells                      the quiet water of the swamps, lay-
Mill and Moraine State Parks. These                       ers of silt and clay and mats of thick
rocks formed during the Pennsyl-                          vegetation (peat) accumulated. As
vanian Period of geologic history                         the rivers changed course or the sea
(approximately 300 million years                          rose to cover the low delta areas,
ago), when a completely different                         the sediments were buried by new
landscape was present, and when                           sequences of peat, sand, and mud.
what is now Pennsylvania was south                        Several times, the shallow sea rose
of the equator. Rivers heavily laden                      and deposited marine clays and
with clay, sand, and gravel flowed                        muds. As each layer was buried,
across Pennsylvania from highlands                        compaction and cementation
in eastern Pennsylvania, New Jer-                         changed the soft, loose sediment
sey, and Delaware. The sediment                           to solid rock. The peat bogs and
was deposited in large deltas along                       swamps became coal. The sand
the shoreline of an ancient sea that                      became Kittanning, Clarion, Home-
covered Ohio and western Pennsyl-                         wood, and Connoquenessing sand-
vania. Thick layers of sand accu-                         stones, and the silts and clays
mulated in river channels and as                          formed Kittanning, Clarion, and Mer-
beaches and barrier bars along the                        cer shales. The thickest marine lime
coast. High-energy waves and cur-                         mud became Vanport limestone.
rents moved some of the sand into                         As the continents moved northward


Cross section through                                    SCALE                                                E
                                                 0                    1000 FT
Slippery Rock Gorge at
McConnells Mill
                                                                                                                  Allegheny Formation




                                                                         Middle             Kittanning
                                                                        Kittanning
                                                                           coal             shale and
                                                                                            sandstone
                          W                                 Glacial
                                                           sediment                  Vanport limestone
                   1200
                                                                              Clarion   Scrubgrass coal
                                                                       shale and sandstone
ELEVATION (feet)




                                          Fallen                                            Brookville coal

                   1100                  blocks of                    Homewood sandstone
                                                                                                                  Pottsville Formation




                                        Homewood
                                        sandstone
                                                                  Mercer shale and coals
                   1000


                                   Connoquenessing sandstone
                    900




                                                     2
about 250 million years ago, the            a large rock on the east bank of the
area was uplifted, and erosion              stream (B). After oil was produced
started to create the landscape as          from drilled wells at Titusville in
we know it today.                           1859, the “Slippery Rock” and other
                                            seeps along the gorge excited local
                                            drillers. By 1864, at least 17 wells
   Mineral Resources                        had been drilled along the creek.
                                            They were shallow but yielded about
The early industrial economy of             45,000 barrels of oil before ground-
the region was based, in large part,        water invaded the sandstones and
on the iron, lime, oil, and coal con-       prevented further oil production.
tained within the sedimentary layers.       Drilling activity then shifted east-
Vanport limestone originally was            ward into the Muddy Creek valley.
named “ferriferous limestone” for           By the 1890s, the Muddy Creek field
the large amount of iron mineral-           was producing oil from formations
ization in the upper part of the            deeper than those tapped in the
member. The iron ore was surface            Slippery Rock Gorge. The produc-
mined in the mid-1800s to feed              tion continued in decreasing quan-
three furnaces—the Wilroy and               tity into the 1930s. As production
Hope Furnaces near Rose Point               diminished, the wells were aban-
(upstream from McConnells Mill              doned but never properly cemented
State Park) and the Lawrence Fur-           and plugged. All of these wells had
nace in Hells Hollow (see the map           to be located and sealed to prevent
on page 9). When the vast iron ore          oil seeps at the bottom of Lake
resources of the Lake Superior re-          Arthur, which covers much of the
gion became available in the 1870s,         old Muddy Creek oil field.
all of the local ore-mining opera-          Most of the minable coal is above
tions and small furnaces were aban-         Vanport limestone in the Kittanning
doned. The ruins of the Wilroy Fur-         Member of the Allegheny Forma-
nace’s stone stack are on private           tion. The Kittanning crops out away
property at A on the centerfold map,        from the rim of the gorge and
but nothing marks the sites of the          around the sides of the Muddy Creek
other furnaces except for some              valley. Much of this coal was mined,
glassy slag scattered on the sur-           both by underground and strip min-
face of the ground. In addition to          ing, before the stringent laws regu-
exploitation of its upper layers for        lating mine reclamation were passed
iron ore, Vanport limestone itself          in the 1960s and 1970s. Conse-
was locally quarried and burned to          quently, before Lake Arthur was
produce agricultural lime.                  flooded, extensive reclamation was
Approximately 6½ miles south of             needed to prevent lake and land
the old gristmill, an oil seep coated       pollution from mine drainage.




                                        3
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The Glacial Lakes and




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                                                                                       Sl
 Slippery Rock Gorge                                                          M         x Kennedy Mill
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Slippery Rock Creek flows in a deep,                                                                   Creek

winding gorge cut into flat-lying                        Slippery Rock-
                                                        Connoquenessing




                                                                                             Run
layers of bedrock. The gorge cuts                             divide                                McConnells
                                                                                                  x Mill




                                                                                            lls
through an old drainage divide, the




                                                                                        ne
                                                                                       on
                                                               He
remnants of a ridge that once sepa-                                 ll




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                                                                                  M
                                                                                       x                            Portersville




                                                                         un
rated streams flowing to the north
                                                                              Cleland




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from streams flowing to the south.




                                                                                                   n
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The gorge is deepest and narrowest




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near Cleland Rock on the divide and         Connoque-




                                                            Wurte




                                                                                       p
                                             nessing




                                                                                   Cam
becomes progressively shallower               Creek                                                                  N

and wider both to the north and to          Elwood         Wurtemburg                                               SCALE
                                             City                                                          0                 2 MI
the south. This is not a typical pat-
tern because the valleys of streams
                                            Preglacial drainage in the McCon-
in areas of flat-lying rocks normally       nells Mill area. Present-day locations
become progressively shallower and          are shown in gray.
wider toward their outlets.
Why does Slippery Rock Gorge have           about the effects of the first two ice
this configuration? The diagrams            sheets because most of their de-
on this page and the next illustrate        posits have been eroded away.
the geologic history of the gorge.          The third known ice sheet to reach
Preglacial Slippery Rock Creek was          the parks moved southeastward in-
joined by Muddy Creek and flowed            to the area approximately 140,000
northwestward from near the pres-           years ago and dammed the north-
ent location of Kennedy Mill (C).           west-flowing Slippery Rock and
From the divide at Cleland Rock,            Muddy Creeks. At the ice-advance
McConnells Run flowed north past            maximum, separate lakes formed
McConnells Mill. Wurtemburg Run             in the Slippery Rock Creek (Lake
flowed south from the divide into           Edmund) and Muddy Creek (Lake
Connoquenessing Creek, 6 miles              Watts) lowlands. A third, much
away.                                       smaller lake (Lake Prouty) also
About 2 million years ago, thick            formed in the McConnells Run val-
masses of continental ice began to          ley, which was dammed south of
accumulate in central and north-            Muddy Creek.
east Canada and periodically spread         Lakes Edmund and Watts drained
southward. At least four of these           south through outlets at their eastern
advancing ice sheets, many hun-             ends (D and E), far from the glacier
dreds or thousands of feet thick,           dam, into Connoquenessing Creek.
reached northwestern Pennsylvania           Lake Prouty spilled over a low point
and modified the landscape and              in the old divide near Cleland Rock
stream patterns. Not much is known          (see page 11) into Wurtemburg Run.

                                        4
It sufficiently eroded the old divide                             the rim. Some of these large blocks
to form the ancestor of today’s                                   moved only a few feet downslope,
south-flowing Slippery Rock Creek.                                but others fell to the bottom of the
As the glacier melted back to the                                 gorge. This widened the gorge, but
northwest, Lake Watts began to                                    left it less deep than originally
drain westward through a series of                                carved (see the cross section on
temporary outlets, each lower than                                page 2).
the preceding. The first of the out-                              During the last glaciation to reach
lets was Alpha Pass (F). After later                              the area, some 23,000 years ago,
drainage through Beta Pass (G),                                   ice-dammed lakes again formed in
the remnant of Lake Watts was still                               the Slippery Rock Creek and Muddy
slightly larger than the present-day                              Creek basins. Drainage from these
Lake Arthur. Finally, Lake Watts                                  lakes further deepened and wid-
completely drained through Gam-                                   ened the Slippery Rock Gorge.
ma Pass (H) on the present Muddy                                  Today, Slippery Rock Creek still has
Creek channel. When the ice re-                                   a steep gradient through the gorge
ceded far enough, Lake Edmund                                     (28 feet per mile compared to 8 feet
drained through Epsilon Pass, past                                per mile north of Kennedy Mill). The
Kennedy Mill.                                                     rushing water has carved potholes
As each pass opened, a short-term                                 in many of the large blocks of sand-
flood surged into the gorge. These                                stone and has scoured out tubes
floods deepened the gorge and                                     through the remaining debris. The
eroded soft Mercer shale beneath                                  combination of rapids, waterfalls,
hard Homewood sandstone, leav-                                    and eddy currents within the chan-
ing the sandstone as an overhang-                                 nel makes for a very treacherous
ing cliff. Because the sandstone is                               stream. These conditions also pro-
cut by many intersecting cracks,                                  vided the waterpower to run both
unsupported large blocks fell from                                McConnells and Kennedy Mills.


                                                                          Slippery Rock
                 N

                            GLACIER                                    Lake
Phases of                                                            Edmund
glacial lake
                                                                                                        West    D
drainage                                                                                                Sunbury
during ice      LAKE EDMUND
                                         H
                DRAINAGE Epsilon
retreat.                                  G                       Lake Watts
Present-day        LAKE  Gamma                 F
                   WATTS                                                                            E
locations        DRAINAGE
                              Beta
                              Alpha
are shown             Maximum             Lake                                                               to Connoquenessing
                                                                                                             Creek
                     extent of ice     x Prouty                                            Unionville
in gray.
                                     Cleland       Portersville
                                      Rock                                                EXPLANATION


                                                                       Lake Watts after   Lake Watts after    Maximum extent
                     SCALE
                 0              3 MI                                   drainage through   drainage through      of all lakes
                                                                          Beta Pass          Alpha Pass




                                                         5
GEOLOGIC MAP OF MORAINE AND                                                                                                                                                                                                                                                               Geology slightly modified from Berg, T. M., Edmunds, W. E., Geyer, A. R.,                                     EXPLANATION




                                                                                                                                                                                                                                                          .
                                                                                                                                                                                                                                             CO
                                                                                                                                                                                                                                                                                          and others, comps., 1980, Geologic map of Pennsylvania (2nd ed.): Penn-
                                                                                                                                                                                                                                                                                          sylvania Geological Survey, 4th ser., Map 1, scale 1:250,000, 3 sheets.

McCONNELLS MILL STATE PARKS




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                                                                                                                                                                                                                                                                                                                                                                                                           Butler
GEOLOGIC FEATURES                             tacular “rock city.” The north exit
                                              road from the mill (McConnells
   IN THE PARK                                Mill Road) passes through a simi-
      Site 1. McConnells                      lar rock city.
      Mill Area                               The intact ledges at the mill dam
The trail from the picnic grounds to          are at the top of Connoquenessing
the mill, the road past the mill, and         sandstone, about 40 feet below
the trail to Alpha Falls—all cross out-       Homewood sandstone and directly
crops and slump blocks of Home-               beneath Mercer shales and coals
wood sandstone. Separation along              (see the cross section on page 2).
vertical cracks (center of the rock
city photograph), downslope rota-
tion of some blocks (left side of the
rock city photograph), and cross-
bedding and pebbly composition in
some layers are visible features of
the sandstone. A honeycomb pat-
tern has also formed on a few weath-
ered surfaces (see the photograph
below). This forms because ground-
water moving through the rock de-
posits iron minerals that are more               Rock city along the exit road
resistant to weathering than the sur-
rounding rock. The iron-rich sand-
stone layers stand out when the                    Site 2. Hells Hollow
rock is weathered.
                                              A short hike along Hells Hollow Trail
At the Rim Road Climbing Area,                toward Hells Hollow Falls takes you
large blocks of Homewood sand-                past a number of features related to
stone have separated from the out-            Vanport limestone and the old iron
crop and slumped downslope to                 industry that flourished in the valley
create open walkways and a spec-              of Slippery Rock Creek during the
                                              mid-1800s (see the map on page 9).
                                              In the streambed adjacent to the
                                              parking lot, sharp, distinct fractures
                                              cut through Vanport limestone. Dur-
                                              ing dry periods, no water flows in
                                              the stream here, but water does flow
                                              in a small cave formed by dissolu-
                                              tion of the limestone.
                                              The Lawrence Iron Furnace was a
                                              few hundred feet upstream from the
      Honeycomb weathering                    third bridge on Hells Hollow Trail.

                                          8
                                                                                                                  Flume




   Fractured Vanport limestone


From the far side of the third bridge,
you might see an entrance to a                                        sinkholes, also formed by limestone
small, long-abandoned (over 100                                       dissolution.
years) coal mine. The entrance is                                     Just upstream from the falls is a
hidden by foliage high on the hill-                                   small quarry where iron ore and
side across Hell Run.                                                 limestone (used for flux) were prob-
Further along the trail toward the                                    ably mined for the Lawrence Fur-
falls, Hell Run flows in a narrow                                     nace. Shortly beyond this, the trail
flume that was originally a lime-                                     ends at Hells Hollow Falls, a pictur-
stone cave. With time, the roof of                                    esque cascade over resistant Cla-
the cave collapsed and exposed the                                    rion sandstone. Vanport limestone
hidden channel. Small depressions                                     is visible here as ledges along the
beside this section of the trail are                                  gorge walls. To the right of the end

                                                  deep
                                                  mine         Ì               HELLS HOLLOW

               fractures
                                     deep
                                     mine
    parking
      lot
                                      Ì       flume

                Lawrence
                 Furnace                                  Hells Hollow
                           x                              Falls
                                                                                      Slippery Rock
                                      Hells   quarry
                                                       lime     He
                                     Hollow             kiln
                                                                     ll                Gorge Trail
                                      Trail
                                                                                       natural
                                                                                       bridges
                                                                          Ru
                                                                          n




                                                                 Vanport limestone outcrops,
                                                               caves, and underground streams
                N

              SCALE                                                                                   to Eckert
        0                  1000 FT                                                                     Bridge
                                                                                                        v




                                                               9
                                               the stream where resistant sand-
                                               stone blocks are particularly large
                                               and numerous in the rubble that
                                               fills the gorge.
                                               More spectacular, high falls occur
                                               on the east side of the gorge. At
                                               Alpha, Kildoo, and Breakneck Falls
                                               (Sites 3, 4, and 5, respectively), tribu-
                                               taries to Slippery Rock Creek flow
                                               across resistant Homewood sand-
         Hells Hollow Falls                    stone and plunge into the much
                                               deeper Slippery Rock Gorge. Be-
of the trail is a brick-lined vertical
                                               Alpha
shaft cut into the rock. This is a lime
                                               Falls
kiln that was used to burn limestone,
probably from the quarry, to pro-
duce lime.
A longer and more rugged trail, Slip-
pery Rock Gorge Trail, follows the
north side of Hells Hollow. It also
has geologic features, including old
coal mine entrances, Vanport lime-
stone outcrops, natural limestone
bridges, small caves, and emerging
underground streams.

      Sites 3, 4, and 5.
      Alpha, Kildoo, and
      Breakneck Falls
Waterfalls of two origins are com-
mon features along the gorge.
Small, low falls, such as Hells Hol-
low Falls, form where a stream in
its normal course flows across hard
rock layers (sandstone and lime-
stone) that do not erode as easily as
weaker layers (shale and siltstone).
This type of falls is the most com-
mon and can be found on almost
every tributary to Slippery Rock
                                                                                   Break-
Creek. The rapids in Slippery Rock                                                 neck
Creek are situated on reaches of                                                   Falls


                                          10
cause the smaller streams could not
erode downward as fast as the main
stream, they enter Slippery Rock
Creek as “hanging waterfalls.” In
the case of Alpha Falls and Muddy
Creek Falls (I), the streams that
form the cascades were outlets for
Lake Watts as the ice retreated
northward and exposed low spots
along the western side of the gla-
cial lake. For a short time, water                             Cleland Rock
from Lake Watts poured over these
lips into the gorge, flushing glacial        south-flowing Slippery Rock Creek
debris and undercutting the sand-            and drained Lake Prouty.
stone rim on each occasion.
                                             After Lake Prouty drained, the newly
                                             created Slippery Rock Gorge was
     Site 6. Cleland Rock                    probably no more than half of its
Cleland Rock is a ledge of Kittan-           present depth. During the last two
ning sandstone that forms a scenic           glaciations (140,000 and 23,000
overlook 400 feet above the deep-            years ago), catastrophic flooding
est part of the 12-mile-long Slip-           from the draining of glacial Lake
pery Rock Gorge. It is also the high-        Watts and Lake Edmund caused
est elevation along the rim of the           the gorge to erode to greater than
gorge.                                       its present depth. Rocks that have
                                             fallen into the gorge from the adja-
Approximately 140,000 years ago,
                                             cent slopes have reduced the depth
a ridge extended across what is
                                             of the gorge.
now the Slippery Rock Valley. The
ridge separated the south-flowing
Wurtemburg Run from Lake Prouty,                     SCALE
                                              0                    1 MI
which lay in the McConnells Run
valley to the north of this divide
(see the sketch of Lake Prouty).
Overflow from Lake Prouty, assisted
                                              N              GLACIER                                                    /19



by meltwater and sediment released
from the nearby glacier, spilled over                                               Lake
the divide at Cleland Rock into Wur-                                               Prouty
temburg Run. This overflow even-                               x
                                                                      S li




                                                             n
                                                                          pper y




                                                           Ru                                                          divid
                                                                                                                             e
tually eroded a channel through                   tem
                                                      bu
                                                        rg
                                                              Cleland                                             in g
                                              Wur              Rock                                      e   ss
the divide at Cleland Rock deep                                                                     u en
                                                                            Ro




                                                                                   ck          oq                     Porters-
                                                                                        - Conn                         ville
enough to join McConnells Run
and Wurtemburg Run. Together
these streams formed the ancestral                       Lake Prouty overflow


                                        11
Slippery Rock Creek has continued               high-level, wave-cut notches or
to erode the gorge since the last               beaches are visible, suggesting that
glaciation, but compared to the                 Lake Watts was short-lived and had
days when water roared through the              only small wave action.
valley, there has been little change.
                                                When Moraine State Park was de-
      Site 7. Lake Arthur                       veloped, the old, depleted oil and
                                                gas wells were plugged, strip mines
Lake Arthur is a smaller, man-made              were backfilled, and deep mines
re-creation of glacial Lake Watts.              were sealed. However, a few traces
Its average elevation is only 1,190             of the drilling and mining can still be
feet (70 feet lower than Lake Watts),           seen. Plugged wells, an oil pump-
and it is about 6 miles shorter than            house, and oil-field debris are on
the old glacial lake. However, the              the hills near Wyggeston Trail (K).
man-made dam is near where the                  Along South Shore Drive, past
ice dam blocked Muddy Creek.                    Pleasant Valley Beach, and at the
Near the middle of glacial Lake                 site marker, a strip-mine highwall
Watts, miles from the gravel re-                shows Kittanning sandstones and
leased from the glacier by melting,             shales. This is the same unit that
only silts and clays settled to the lake        forms the Cleland Rock overlook.
bottom. When the Pa. Route 528                  Kittanning coals were also strip and
bridge (J) was being built, initial             deep mined on the north shore of
construction had to be halted be-               Lake Arthur. Evidence of this min-
cause the 90 feet of water-saturated            ing can be seen along the bike trail
silt and clay was not able to support           between mile 7 and the trail end (L).
the bridge, and the bridge had to be            Look for sandstone blocks, rusty
redesigned. Although Lake Watts                 seeps from pits, and small waste
stood higher than Lake Arthur, no               piles on the north side of the trail.




Lake Arthur,
Pleasant
Valley Beach,
and old strip
mine




                                           12
                                                           ited in a channel confined within
                                                           the ice, rather than in a channel
                                                           eroded into the ground. The 6-mile-
                                                           long Jacksville Esker (known lo-
                                                           cally as West Liberty Hogback and
                                                           Miller Esker) formed during the
                                                           last glaciation, about 23,000 years
                                                           ago. Although its central portion is
                                                           eroded, the Jacksville Esker is the
                                                           best preserved esker in Pennsylva-
       Strip-mine highwall along
           South Shore Drive                               nia. The portion of the esker visi-
                                                           ble from the marker is owned by the
                                                           Western Pennsylvania Conservancy
        Site 8. Jacksville Esker                           and is open to the public. Stay near
        Glacial Deposit                                    the tree line as you walk to the top
Although both parks are the result                         of the esker to get a feel for its size.
of glaciation, neither contains easily                     Swope Road cuts through the esker
observable, characteristic glacial                         (M), exposing the sediments. The
deposits. The closest glacial feature                      gravel and cobbles range from lo-
of note is the Jacksville Esker, 2½                        cal sedimentary bedrock to meta-
miles north of Moraine State Park.                         morphic and igneous rocks trans-
An esker forms when meltwater                              ported from Canada by the glacier.
drains into a glacier through frac-                        Because sand and gravel are valu-
tures and then flows through ice                           able sources for roadbase, concrete
tunnels at the base of the glacier.                        aggregate, and other construction
Sand and gravel deposited along the                        materials, parts of this esker and
tunnel floor remain as an elongate,                        other glacial deposits are disappear-
commonly sinuous, ridge when the                           ing rapidly through economic ex-
ice melts. Esker sediment is depos-                        ploitation.

Photograph courtesy of Bradford B. Van Diver from Van Diver, B. B., 1990, Roadside
Geology of Pennsylvania: Mountain Press Publishing Co., Missoula, Mont., p. 72.




                                            Jacksville Esker

                                                     13
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                       MERCER                                                                                                                                        VENANGO
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                                                                                                                                                    138                 38
                                                                                                                                                                Muddy
                                            McConnells Mill                                                                                                     Creek
                                              State Park
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                                           av
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                                                                          u   ene                                                                               BUTLER
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                                      60                                                     g                                         Cr
                                                                                                                                                      8
            BEAVER                               Beaver
                                                  Falls




                                  For more information on either park,
                                  contact
                                                             Moraine State Park
                                                         225 Pleasant Valley Road
                                                        Portersville, PA 16051–9650
                                                               724–368–8811




An Equal Opportunity Employer                                                         Recycled Paper                                                                          2200–BK–DCNR3113

								
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