Brief overview of where the week will take us:

• Day 1-- Indian Echo Cave and Millersville University Weather Center
• Day 2 -- Lebanon County Quarries, Landfill, and Rexmont Dam
• Day 3 -- Cornwall Iron Furnace, Cedar Crest High School Planetarium
• Day 4 -- Agricultural Centers in Lebanon County, Fossil Outcrop, Swatara Creek, Night Sky Viewing
• Day 5 -- Anthracite Coal Mines, Centralia Mine Fire, and Roadcuts
• Day 6 -- Rickett's Glen State Park
• Day 7 -- Penn's Caves

Check out the quick reference chart below, or read the passages below for more, in-depth information on the Geology, Biology, Climate, and Environment of Central Pennsylvania:
 
 

Early Earth--Proterozoic Eon:

Approximately 1.2 billion years ago, the Laurentian continental crust block was being formed by the accretion of many microplates.  One of the last accretions to the Laurentian block formed metamorphic rocks called Grenville rocks (which are mostly gneiss).  These Grenville rocks are believed to underly all of Pennsylvania, and are only exposed at the surface in southeastern PA.  These Grenville Rocks at this surface location  have been radiometrically dated to 1.2 billion years ago.

Approximately 250 mill. years later, the Earth's convection currents caused rifting in this region which formed crevasses in which river's could deposit sediments, and volcanoes and fissures in the Earth's crust could allow fresh lava/magma to cool and solidify into igneous rocks.  While this was occuring in Pennsylvania, to the east of the state, the Iapetus Ocean was forming.

This was the time period during which life first developed--first in the form of unicellular organisms which then evolved into multicellular organisms such as stromatolites (algae), worms, and other soft-tissued, sea-dwelling organisms.

Paleozoic Era:

At the beginning of the Cambrian Period(about 570 mya) the Iapetus Ocean transgressed onto the North

©Pennsylvania DCNR

American continent.  This now placed the northwest and north-central regions of PA under a shallow sea with a sandy bottom.  The rest of the state was under a shallow sea with a carbonate bottom.  This would be the origin of the limestone rocks commonly found at the surface today in central and south-central Pennsylvania.  During this time period, PA was also located just south of the equator so the region was experiencing a warm, humid, tropical climate.  Due to the shallow marine environment during the Cambrian,

many trilobites and brachipods lived here.  These organisms have been preserved in the carbonate rocks of this region and time frame.

The Ordovician Period followed the Cambrian with some dramatic geologic occurrences.  Subduction  occurring eastward across the Iapetus Ocean from North America formed a volcanic arc.

occuring eastward across the Iapetus Ocean from North America formed a volcanic arc.  This subduction of the oceanic crust under the  continental crust eventually caused the collision between the volcanic arc (along with parts of the oceanic crust) and the North American plate.  The volcanic arc and oceanic crust materials that were thrust on top of the North American material caused the eastern portion of the North American plate to subside.  This collision, which formed the Appalacian Basin (due to the subsidence) in

©Prentice Hall, Introduction to Physical Geology

western Pennsylvania and the Taconic Mountains in eastern Pennsylvania was called the Taconic Orogeny.  As water flowed westward from these mountains, the rocks were eroded.  These silt, clay, sand, and gravel particles were now being deposited over the carbonate particles left from the shallow sea.  This is the basis for limestone rocks to be overlain by the clastic sandstone and shale rocks in the central PA region.

This major geologic event was disasterous to some organisms; however, organisms such as bryozoans, molluscs, corals, and graptolites survived the ecosystem change.  Their survival was probably due to the fact that they are marine organisms, not land organisms.

The Silurian Period saw less dynamic processes and more erosional processes.  As the clastic sediments were eroded away from the mountains, they were being deposited in all regions of Pennsylvania.  As these sands and gravels (made mostly of quartz) were deposited, they were being cemented and compacted together.  These new sandstones are what is now called the Tuscarora Formation and it can be found in the Appalachian Mountains.  This rock is very resistent so it forms some of the highest peaks in this region.  Chemical weathering of the mountainous rocks released iron which was precipitated out in the inland sea---this was the source of the iron that was mined in central and western PA in the early 19th century.  As the Taconic Mountains were eroded away, the inland sea was beginning to evaporate.  This evaporation slowly allowed the deposition of more limestones and dolomites in the central region---as the water was getting shallower and shallower.  As the sea was further heated and thus evaporated (receeding towards the northwestern edge of Pennsylvania) halites and gypsums were allowed to crystallize out of the supersaturated water.  These evaporites were deposited in the western area of the state.

Due to the warm, shallow seas, corals thrived in the region (fostering the formation of coral reefs in the vacinity of central Pennsylvania).  The Late Silurian also saw the evolution of fish.  This evolution allowed them to progress from saltwater environments to fresh and brackish water bodies.  The Silurian was also important to plant life because this was the period when plants began rooting on land (which could now be a food source for future land dwelling organisms!)

The beginning of the Devonian Period was calm, geologically speaking.  There was a continuation of carbonate deposition, but towards the end of the period (about 360 mya) the Acadian Orogeny occured.This collision between Laurentia and Baltica formed a continental-continental plate boundary (thus closing the Iapetus Ocean). The intense pressure and folding created more metamorphic and

©Thomson Learning, Historical Geology

igneous rocks in the eastern PA region as the Acadian Mountains (Highlands on the diagram) were formed.  As the pressure continued, and the mountains were thrust upward, they were also eroded.  The sediments wee transported to the Appalacian Basin where they formed black and gray shales and siltstones across most of the state.  As sediments continued to fill the basin, an alluvial plain was formed which allowed the sediments to settle out as course grains were deposited near shore and finer sediments farther

into the water filled basin.  As the sediments continued to accumulate, a regression of the sea is evident in the pattern of the sediments deposited on top of one another (making a great environment for future oil storage!)  As the Acadian Mountains continued to be eroded, the newly created sediments now formed red clastic rocks that form the Catskill Delta (also known as "red beds").  The oxidized iron is indicative of a seasonally dry warm climate.  The seasonally wet periods can be examined through the fossil evidence left by fish, amphibians, insects, and arthropods which had now begun to inhabit the land region.

The Carboniferous included two extremely important Periods in Pennsylvania's geologic history:  the Mississippian and the Pennsylvanian.  As the climate changed to include more rain, the red-oxidized
 

sediments that were being eroded from the Acadian Highlands at the end of the Devonian were no longer being oxidized.  So the beginning of the Mississipian can be viewed as the Acadian sediments no longer appeared red, but now were being deposited as gray particles.  As the climate changed again, there is evidence of the iron in the rock oxidizing to form re dediments (hematite--iron ores).  As this was occuring, carbonates were still being deposited in western PA due to a shallow sea there (Appalacian Sea).  As the Pennsylvanian began, the area of alluvial plains at the edge of the sea became covered with swamps with ferns and huge trees and lush vegetation.  These types of vegetation thrived here due to the location just below the equator.  As the trees and plants died and piled up in the water (so they were not oxidized), peat was formed.  As erosion continued, these dense peat marshes were covered with sediments which, upon adding weight to the peat, allowed the carbon to become concentrated and eventually

©Thomson Learning, Historical Geology

form coal.  As the coal was formed by pressure, Bituminous was made first (containing about 80% carbon) and then as heat and pressure continued, Anthracite was formed (containing about 98% carbon).  The only places in Pennsylvania that anthracite is found is in the east-central region of the state.  It is the more fuel efficient of the two due to the higher carbon and zero sulfur content.

As the sediments continued to accumulate on the swamps, the alluvial plain moved westward, eventually drying up the Appalacian Sea.  The multiple seams of coal in the region can be attributed to the rise and fall of river and stream levels which allowed the peat to accumulate in the eastern portion of the state.  (It takes 10 feet thick of peat to form a one foot thick seam of coal.)  As these forests flourished, so did the animal life.  Amphibians, reptiles, snails, and insects thrived in these lush woodlands.  This is why so many ferns, and snail fossils can be found in and around coal beds and other rocks formed during this time period.

The Permian Period saw the collision of Africa with the North American continent (as Pangea formed)

©Thomson Learning, Historical Geology

which created the Alleghanian Mountians in what is referred to as the Alleghanian Orogeny.  The Piedmont Province (south-east PA) has evidence of the rocks thrusted upward due to this mountain building event.  This orogeny is what caused much of the synclinal and anticlinal formations isn today's Appalacian Mountain chain.  As time progressed, this newly uplifted and faulted region under-went erosion which allowed more sediment to be deposited in the western part of the state (forming shales and sandstones).  Because Pennsylvania was situated in the

center of Pangea, there is no evidence of carbonate or swamp deposition due to the lack of water supply.  Because of the decreased water supply, at the end of the Permian, the amphibian population declined and the reptile population began to thrive in the region.  This extinction of many species is known as the greatest mass extinction in the history of the Earth.  The actual cause of it is still under investigation, today.

Mesozoic Era:

The Mesozoic Era consists of the Triassic, Jurassic, and the Cretaceous Periods.  This era signified a major change in the development of the state.  Due to the uplift from the Alleghanian Orogeny, the

©Thomson Learning, Historical Geology

region was now no longer below sea level--meaning, it was no longer a depositional basin.  Also, with the break-up of Pangea, due to sea-floor spreading and continental drift now occuring, the climate was changing as the region began to move closer to its present day position.  This rifting allowed new igneous rocks (diabase) to be formed in the rift zones now being created along south-eastern PA (called the Gettysburg-Newark basin).  Also, due to the newly formed Atlantic Ocean, a new drainage

pattern was established for the state---allowing western waters to flow into the Mississippi River basin and eastern waters to flow into the Chesapeake Bay (and then the Atlantic Ocean).  Because of the newly established drainage basin, chemical weathering, along with mechanical weathering, became an important agent in the formation of the Pennsylvanian rock features.

The Mesozoic saw many land organisms evolve--such as dinosaurs, birds, land mammals (late Triassic), insects, fish, etc...  However, many of these organisms became extinct at the end of the era due to several hypothesized reasons (i.e. asteroid impact).  Even though the mass extinction at the end of the Paleozioc Era was a much greater loss, the extinction at the end of the Mesozoic is remembered better due to the loss of the dinosaurs.

Cenozoic Era:

The Cenozoic Era followed the Mesozoic and is divided into two periods, the Tertiary and the Quaternary (which we are presently in).  During the early Tertiary, very little mountain building occurred.  The dominant geologic creation during this time was the formation of beds of saprolite.  Once the end of the Tertiary was approaching, the climate became a little cooler and drier (due to the fact the landmass was still moving northward).  This allowed more erosion to occur.  As eastern Pennsylvania became more eroded, many of the streams, rivers, and tributaries that we have today (like the Juniata, Susquehanna, and Schukill Rivers) became established in the drainage basin.

During the Pliestocene Epoch (early Quaternary) three continental glaciers moved into the northeast section of the state (the first came about 800,000 years ago, the last was here about 24,000 years ago).  The advancing glaciers caused huge valleys to be scraped out of the underlying shale and siltstones.  the areas boardering the ice sheets experienced periods of freezing and thawing which allowed the rocks to crack.  Once the ice sheets melted, gravels, sands, clays, and silts were redistributed (as till) throughout the region (and valleys).  This glaciation is believed to have helped bring the region's climate closer to what it is today.  This climate change is also what now allowed land grasses to thrive.  This introdution of land grasses in turn allowed land mammals to become abundant in the state, such as deer, rabbits, squirrels, chipmunks, skunks, etc...

As can be seen, Pennsylvania has a very rich geologic history.  Through association with water bodies, limestones, sandstones, and coals have been deposited.  Also, through plate tectonics, mountains, valleys, and igneous/metamorphic rocks have been formed.  Through this, the changing climate has helped to foster the chemical weathering and physical erosion of these land mass features---and also has helped to establish the evolutionary biome that the state has allowed to flourish.

Read more about the climate and environment of the state, below.  Then delve into the seven day trip to find out more about specific sites within central Pennsylvania!
 

Well, if you read the "Geologic and Biologic Time Progression of Pennsylvania" section of this page, then you got an idea of how the region's climate has helped to enhance geologic effects on the surface (such as chemical weathering and physical erosion).  To summarize the past environments:  PA was situated over the equator (or slightly south of it) for millions of years.  This allowed hot, humid conditions to exist year

round.  As the continental landmass began to move northward a the beginning of the Mesozoic Era, the state's climate changed to a subtropical region with much of the year being dry with rainy seasons.  There were also very long dry/wet seasons about every several thousand years.  As the continent kept moving northward, the climate got wetter---allowing land vegetation to flourish.  The end of the Tertiary is when local climates became closer to what they are today (cooler and drier conditions).  Of course, the Quaternary (Pliestocene) glaciers dropped overall temperatures drastically.  Now, during the Holocene, Central Pennsylvania  (located at approximately 40º N latitude) is situated in a Humid subtropical climate [Cfa on the map], which is commonly found on the eastern sides of continents between 25º - 40º latitude.  The summers in central PA exhibit hot, humid temperatures, with daytime temperatures ranging from mid 80's to low 90's (ºF).  Due to a high mixing ratio and relative humidity, the nights usually cool to the mid to lower 70's (ºF).  There are

©Prentice Hall, Climatology

frequent thunderstorms in the summer (on average about 70 days per year experience these types of storms) due to the warm, moist air from the Atlantic Ocean and also the maritime tropical air being heated over the continent as it makes its way from the Pacific Ocean or Gulf of Mexico.

The winters in central PA are diffent because the warm, moist air masses that move across the state are now cooled.  Since the cooler air cannot hold as much moisture, the dominant precipitation in the region during the winter months falls as snow.  The average temperatures in winter are low 30's (ºF) but with the windchill, temperatures can drop into the negatives!

The region gets about 40 - 50 inches of precipitation each year.  The precipitation is distributed among all four seasons.  Autumn and spring are transition zones between the hot, humid summers and cool, dry winters.  The region can go through some drought episodes (i.e. summer of 2002).  These drought periods force the region to observe water conservation methods--such as no car washing and no watering of lawns.  The drought seasons and rainy seasons seem to go hand-in-hand, though, as this summer we are experiencing an abundance of rainfall.

Overall, the climate of the region, today is humid, subtropical.  We experience both hot, humid periods, and cool, dry periods.  The region's weather varies greatly.  We could have sunny, clear skies one day, and thunderstorms and tornadoes the next day.  The weather in central PA is never boring to study!
 

Due to the major profit operations in the state attributed to some sort of land-use occupation, environmental concerns are always discussed at the state level.  The two major land uses affecting the central Pennsylvania region are mining and farming practices.
 
 

Dealing with the first, mining, central PA has been a little fortunate with where the coal is located.  Most of the coal in the center of the state is located in seams that run to great depths and can be as wide as 100 feet thick.  In order to mine the seams at such depths as 200 feet below the Earth's surface, miners had to create mine shaft systems that tunnelled through the Earth to get to the actual coal seam.  The only surficial damage associated with with this type of mining was associated with the are where the operational machines were set-up and places where the mine shafts breached the surface.  There are still regions in central PA that are unsafe for hikers due to the shallow depth of the mine shaft ceilings!

Photo by Tricia Schafebook--from Ashland Anthracite Museum

The second yped of mining practiced in central PA is strip mining (or open pit mining).  Strip mining is done when the seam of coal is parallel to the surface and if not at, then right below the surface. (versus the intense dip angles of the coal shown in the above diagram)  Miners then remove the overlying rock and "strip" the seam of coal away.  The major problems with this were the cration of barren lands when the coal was removed and the release of sulfur which caused extremely acidic water to runoff the newly exposed land surface.  This type of method is commonly used in the mining of bituminous coal---remember, as stated in the "Geology" section above, anthracite was made by the intense heat and pressure created by the cratons colliding.  This heat and pressure is what also created the folded appearance of the rock layers.  Bituminous coal hasn't undergone that great compressional force, so it can still be found in flat layers below the Earth's surface.  To regulate strip mine operations, The Surface Mining Control and Reclaimation Act (SMCRA) was passed to monitor environmental harms to both ground surface and subsurface.  It also monitors the quality of area waters before, during, and after mining operations to help maintain appropriate pollutant levels.

Open pit mining is similar to strip mining in that it entails the land surface to be destroyed to obtain rock materials at some fairly shallow depth below.  Instead of stripping layers of the land surface away, though, a big, tiered pit is dug to gain access to the rocks desired.  This method of mining is commonly used to obtain limestones, slates, and marbles in this region.  These are known as "quarries" and there are still many of them in the region, today.  As with the other two mining methods, this one is also regulated by the state and federal government to ensure proper water contaminate levels and land-use rights.

Farming is also an extremely common practice and occupation in central Pennsylvania.  Over 50% of land in both Lebanon and Lancaster Counties are set aside for farming practices.  There are numerous laws created to protect the agricultural industry, but there have also been numerous laws created to regulate it.  Growing Greener laws within the state are trying to help educate farmers on how to practice more environmentally sound farming duties---it even offers grants to those farmers willing to change to more land-friendly practices.  A lot of the potential pollution sources stem from animal wastes.  Being high in nitrates, when manure is deposited y animals, or placed on fields as fertilizers, these nitrates enhance growth of crops and grasses.  However, it also is absorbed into the ground (thanks to bacteria) and can reach the ground water supply which can end up in neighboring drinking wells.  Also, some farmers allow their livestock access to streams on their properties.  Doing this allows the contaminants to be transported even farther distances through the surface water supply.  The state is trying to get farmers to block livestock from access to surface streams, but some people see no need because they consider the stream to be theirs, since it runs through their property.  Right now the government is focusing on educating the agricultural community members and leaders so they can make sound environmental decision.  If this tactic does not work, the government will need to resort to other law-forming measures.

Now that you have had a chance to read up on the geology, biology, climate, and environmental impacts of Central Pennsylvania, why don't you partake in the one-week course in the region that I have prepared for you!

See what I have in store for you!
 
 

Resources and Useful Links for the Seven Day Trip	Trip requirements, information, and travel arrangements	Day One
Day Two	Day Three	Day Four
Day Five	Day Six	Day Seven
Introduction Page	One-Day Field Trip	Glossary