Some questions regarding local geology

I thought I would write this blog using some common questions.  I haven’t received many questions from the readers, but I do thank you for your comments.  I hope some of these blogs helped you understand geology better or aided in some aspect of history or geology.  Asking questions in a great way to find out more information and I don’t mind answering them.  If I don’t know the answer, I have contacts that might.

Probably the most asked question or misunderstanding is where were glaciers located in Pennsylvania? Well, the ice line was south of Scranton and actually located well within the anthracite coal belt of northeastern Pennsylvania.  In central Pennsylvania the great wall of ice made it as far south as about Shamokin Dam north of Selingsgrove.  Northwestern Pennsylvania was also covered with glacial ice.  That means that there was never any glacial ice covering a section of our region.  Because of their appearance, many folks think the conglomerate exposed on the top of the Hellam Hills, such as RockyRidgeCountyPark in SpringettsburyTownship and Chimney Rock in HellamTownship are great examples.  This is actually one of the oldest sedimentary rocks in the state anf not involved in any Ice Age formation.  I wouldn’t say that our area was never affected by the Ice Age.  When the ice was melting about 10,000 years ago, much water was sent down the Susquehanna River, doing rapid downcutting into the landscape and laying the foundation for our topography in the River Hills.  Should you want to read about a Ice Age sinkhole in YorkCounty, search back into this series and find one written on Bootlegger’s Sinkhole near Emigsville.

Map showing locations of the glaciated areas in Pennsylvania

Map showing locations of the glaciated areas in Pennsylvania

Another question would be Ski Roundtop.  Many folks in the northern part of the county believe this popular ski resort was a volcano.  I can see where that impression comes from.  From our home, we can see the peak and it looks like a volcano.  Well, was it?   Using present-day evidence of rock exposures there, we do not see any volcanic rocks that point to that evidence.  Yes, there are igneous rocks there known as diabase, but these rocks formed deep within the Earth from magma that never made it to the surface.  Nicknamed “ironstone” this rock is massive and very hard. Diabase is very common in northern YorkCounty located within what we call the Piedmont Gettysburg-Newark Section of Mesozoic Basin.  The same rock is found at Devil’s Den and Little Roundtop on the GettysburgNationalMilitaryPark.  If Ski Roundtop was a volcano, all evidence has been eroded away, which is possible since 4-5 miles of our crust has disappeared since 140 million years ago.

Geologic map of the Ski Roundtop area.  Red represents diabase.

Geologic map of the Ski Roundtop area. Red represents diabase.

What other economic minerals were mined in YorkCounty besides iron?  Another good question and those mostly interested in mining history.  If you are not aware, there were at least 170 different iron operations in YorkCounty between the 1770’s and 1910.  YorkCounty was one of the leading iron ore districts in our state and is often overlooked by historians when they are trying to highlight the important early industries.  Back to the question at hand.  Copper was exactly removed from a shaft in the early 1900’s along Bull Road along the Dover-ConewagoTownship line.  Several friends of mine remembered accessing the shaft in the 1950’s.  Today a depression into a hillside represents the shaft.  No name has been found associated with this small operation.  Another small copper operation was located in ManchesterTownship north of Roundtop.  Known as LeCron’s Prospect, this vertical shaft has fallen in and is located in a heavily overgrown woods.  It was reported in the 1890’s that a tooth of a Triassic-aged reptile was recovered.  Small copper mineralization is occasionally found in the northern YorkCounty area mostly that of malachite.  The famous azurite-malachite hole along Old York Road north of Rossville is such an example.  A small amount of lead in the form of the mineral galena was reported in the 1800’s in Frystown, what is now East Philadelphia Street near Sherman Street.  No mining of the galena has been reported.

The Rossville azurite and malachite hole

The Rossville azurite and malachite hole

There has been a family lore story for many generations regarding gold near Airville.  Supposedly, a father and his two sons were prospecting gold from a nearby stream in the 1820’s.  The one son felt he was not receiving his percentage of profit from the work and murdered his brother and father, spending the rest of his life in prison.  There  has not been a report of gold mining in YorkCounty although about 15% of the streams in the county contain gold.

A pan showing magnetite, a heavy mineral found with gold

A pan showing magnetite, a heavy mineral found with gold

Another question is regarding faults.  Are there any faults in the area?  This question is often introduced after a major earthquake somewhere in the world and the faults are discussed.  Yes, faults are actually common in most regions and especially in an area such as ours that contain old rocks and have been through several episodes of continental wrecking and splitting.  The Martic Line that crosses YorkCounty in the southern section is probably the most famous fault.  However, the YorkValley where U.S. Rte. 30 runs probably contains the most faults.  If you have a chance to visit one of the area limestone quarries, you can’t miss faults on the walls.  Now are any of these faults still active?  Based on what we have observed, the answer is no.  Although the area has had several earthquakes, we are not certain that they are a result of the release of energy along one of these faults.

A fault exposed in the York Building Products Westgate quarry.

A fault exposed in the York Building Products Westgate quarry.

Finally, did we have any volcanoes in York County?  Well yes and you would know this if you are a faithful follower of the blog.  There are volcanic rocks found in the Hellam Hills (exposed at Accomac), the Pigeon Hills (exposed along Beaver Creek Road), along the York County Heritage Rail Trail between Glen rock and New Freedom and along the shore of the Susquehanna River at Holtwood Dam.  All of these rocks are related and are about 600 million years old and formed as a result of an early supercontinent known as Rodinia rifting apart.  If you are familiar with the mid-oceanic ridge, this is how these rocks were formed.

Metabasalt from southern York County

Metabasalt from southern York County

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So why should WE teach earth and space science?

I just finished giving my Earth and Space Science class their Final test this afternoon.  Things always get hectic at the end of the semester as some of the students get nervous about their grades and those missing some lab assignments need to submit those to get some credit for the work.  In a way, it is sad that the semester had to end.  This group of students I had this spring was a great bunch to work with.  They seemed to be interested in what they were learning, doing well on completing the lab exercises and enjoyed being outdoors.

This was my second year at MessiahCollege.  I only teach this course every spring as the demand for this course isn’t strong enough to teach both semesters.  After my 2012 initial teaching experience, I learned how Messiah worked, the quality of the students going there and a better idea of what works and doesn’t work.  I went into this year with a better idea of what to teach and how to present it.  Most importantly, unlike 2012, I forced the students to purchase a lab book.  Last year,  I copied lab exercises out of other manuals I had which did not always do well.  With a lab manual the labs were more organized and more rewarding to the students.    I do have the freedom to pick and choose the weekly topics that will be covered.  This works well as I found out from last year what topics went over like a lead balloon, as the saying states.  However, the little catch is that my supervisor has asked me to include several weeks of oceanography and meteorology, neither of each I know much about.  So, there I go, learning just like the students and thanks to PowerPoint lectures to guide me.   I don’t pretend to know much about these two subjects and I admit to the class that I am not an expert.  Yes, I like to watch weather and am a daily observer to the sky trying to predict what is coming, but I don’t understand the concepts.

So why do I like to teach all ages about the Earth and space?  I really can’t answer that, but I just like talking to anyone about the fields.  Yes, I know that the Messiah College students are taking the course for a required lab credit, but I hope they retain just a small piece of information about the school year is over.  I even indicated several times in class that some of these themes can be useful in buying a house of property.  How about if you buy undeveloped property and need to drill a well?  Dig out your textbook and lab manual and refresh on some of the basics of groundwater.  Should I be living in an area with metamorphic or sedimentary rocks?  Which rock is better to build on for a durable foundation?

During the semester, the students have three “out-of-the-classroom” experiences.  In late April we spent a hour under the stars.  A good friend of mine, Dick Copper, brought his telescope on campus for viewing Jupiter, the Orion Nebula and a star cluster.  Dick teaches astronomy labs at GettysburgCollege.  Also in late April, we went on a 3 hour field trip throughout northern YorkCounty to visit several roadcuts to show the students some concepts we had talked about in class.  The best way to teach earth science is to spend time outside putting your fingers dirty.  Our last class together we went to a local private-owned cave and ended the semester panning for gold in Stoney Run.  I wish everyone could have seen the caving portion.

I took the group to LisburnCave.  I visited the quarry some time ago and realized just how little I like tight spots.  Much of the cave only  has 2-foot high ceilings and you have to like seeing clay closeup as you navigate through the 150 feet of hallways.  Out of my 16 students only 9 individuals choose to go into the cave.  No problem I could relate to those not wanting to experience true darkness when all of lights were turned off.  Because I had to give all of my flashlights out to those not equipped with lights, I remained just inside the cave opening in case there was a problem.  After 45 minutes, I heard voices as the crew was coming out.  They all came climbing out of the opening with smiles and their  faces and muddy.  They actually worked together as a team conquering what some were fearful of, crawling through water and mud ands squeezing through tight spots.

It is always fun to take families on fieldtrips.  You never know how people will react when they find a fossil.  I still remember when a 12 year old found a worm tube fossil.  The expression on her face was priceless.  You would have thought that she just won $1 million.  That is a quite rewarding feeling to see those reactions.  I have said it before that when you break open a rock and expose a fossil, you are the first person to see that particular specimen.  Now that is cool!!

I worry about the new standards coming out for the secondary school level.  I am uncertain just how much earth and space will be included.  The rapid scientific discovery going on with Mars and the remarkable pictures taken by the Hubble Space Telescope certainly keep astronomy in the headlines.  But what about geology?  Perhaps some people look at geology as a low priority.  Just what can we do on a computer to teach the subject.  That appears to be the theme these days,  No more  field trips looking at rocks, mineral and fossils, but look what a computer can model when working with a theory.  In my book, that doesn’t sound like fun.  Remember, earlier, I said that the best way to teach geology is go out and touch it.  I don’t think you get the same experience when moving your mouse back and forth across the computer screen.  Time will tell where the priorities will be with the new standards.

I teach because I enjoy it.  Even talking to senior citizens is really cool.  If you are senior citizen and looking for some enrichment in education, check out the OLLI program at Penn State York.  What a great program with a wide assortment of classes offered.  If you can’t find anything in their catalog that hits a nerve, you better start reading the catalog from the back to the front.  The fee to belong to OLLI and course registration is only about the same amount as you and a spouse going out to eat at a fancy restaurant.  I teach every fall for several weeks   a geology class of some sort.  This coming fall I will be doing several of my favorite “canned” PowerPoint programs in geology and astronomy.   I will also be teaching an experimental course on  “Geology of Tourist Attractions” in the East.

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Mineral resources of South Mountain and Frederick Valley, Pennsylvania and Maryland

Stop 1. Specialty Granules Corporation, Charmain Road, Blue Ridge Summit, Blue Ridge Summit, PA Geologic Formation: Catoctin of Precambrian age Rock type(s): Metabasalt (greenish) and metarhyolite (reddish) (volcanic) We are grateful and excited about presenting this stop to you. Thank you goes out to Greg Oliver and Charlie Poulson of Specialty Granules for all of the pre-fieldtrip planning and our tour today. They have volunteered to come to the operation to host our tour and their assistance is greatly appreciated. It is hoped that you will see how valuable quarries are, appreciate how technology is used in producing their finished products and realize how many regulations such an operation as Specialty Granules has to follow from the local to federal levels of government. Below are highlights of this operation: Acreage Owned: Over 700 acres Duration: Have been here for 90 years Crushing and screening: Metabasalt is screened from 1.5” to granules Products Producing: Roofing granules in 16 different colors for mostly GAF, Tamaco and Elk Process: Granules are colored and fired. Also produced are unfired, uncolored granules that do not specs. Amount: 600,000 tons shipped of metabasalt granules Transportation: 80% of products are moved by trucks; 20% by railroad Employees: 140 with an average length of service of 17 years Quarry Depth: Current quarry is permitted to 8 levels (approximately 400 feet) Old quarry was down 7 levels (350 feet) but has been back-filled about 250 feet Conveyors: Have 0.75 miles of conveyors to transport rock to different plants and processes Undersized: Have about 50% of the material (600,000-700,000 tons) which is recycled and reclaimed back into quarry Blasting: Once every 7 – 10 days. Have 2 portable seismographs that are deployed out to closest Residences to monitor ground shaking. Problems: The operation often encounters the metarhyolite which no use for is known as this time. Groundwater: No issues since the bedrock is non-permeable and had no porosity Property Border: A beam surrounds the entire border, plainly marking a “Do Not Enter” area. Wildlife: Actual the property can be viewed as a wildlife refuge. Whitetail deer, turkey, bear, coyote, fox, raccoons and birds love this habitat. Other: Have a pond to settle out sediment before entering back into the watershed. Water re-entering watershed is probably cleaner than stream water. Have a on-site weather station to monitor conditions, i.e. for blasting. Geology: Metabasalt and metarhyolite are both igneous rocks that originated from lava. The word” meta” has been placed in front of each rock name because the rocks have undergone metamorphism through crustal plate collisions. Rhyolite forms from volcanic activity on continental crust and basalt is the major component of oceanic crust. These rocks originated as a result of the breakup of an ancient supercontinent known as Rodinia that split apart starting about 700 million years ago. Later, a collision with a chain of volcanic islands and the coming together of Africa and North America caused heat and pressure, slightly altering the rocks. On the tour, we will try to show an example of folding and faulting in the rock.

Specialty Granules quarry

Specialty Granules quarry

Point of Interest A Native Copper Mines in South Mountain Location: From near Mt. Hope southward to Pa. Rte. 16, mostly associated with Copper Run. Once belonging to the P. H. Glatfelter Company of Spring Grove, PA as one of their tree farms, many of the mines are today situated within the Michaux State Forest. Several mines were known on the property of Specialty Granules as well as near the “Underground Pentagon.” The first copper operation was reportedly opened in 1833 and became one of the country’s leading copper districts in the late 1800’s. The last major mining operations shutdown in the 1920’s. Occasional attempts and rumors to start new mining continued into the 1960’s. The area became known to “rockhounders” after several reports were published by geologists in the early 1900’s. The district was also publicized in the “Mineral Collecting of Pennsylvania” published in 1976 by the Pennsylvania Geological Survey. An assortment of minerals, including native copper, have been found on the mine dumps. It was reported that native copper was found during the construction of the “Underground Pentagon.” Specialty Granules also finds native copper during quarrying. Native copper is common within volcanic rocks. The Keweenawan copper deposits in Michigan is geologically similar to South Mountain. Most of the copper is found within the metabasalt and quartz veins associated with this rock. The green color of the metabasalt is not from the copper, but rather epidote and chlorite. The copper was formed from deep groundwater containing the native element, which leached toward the surface rocks undergoing hydration. Weathering of the surface rock created secondary minerals such as malachite, azurite and cuprite. The quartz veins were formed in similar fashion where silica and copper ions crystallized from hot groundwater caused by metamorphism. The groundwater found it’s way into cracks within the metabasalt, cooled and formed the copper-bearing veins. For a detailed description on the history of this copper district, go to http://www.pennminerals.com/Chronicles2.htm.

Jeri and Roxann at the Reed Hill copper mine near Mt. Hope

Jeri and Roxann at the Reed Hill copper mine near Mt. Hope

Point of Interest B Devil’s Race Course, Fort Richtie Road, Franklin County Location: Parking area is located on the west side of Ritchie Road about 0.75 mile north of the intersection of Md. Rte. 491 (Raven Rock Road). Although there is a similar occurrence with the same name just northwest of Specialty Granules, we are going to drive past this Maryland occurrence. Although time does not permit us to stop, please come back and visit this geologic feature. The Devil’s Race Course is known as a boulder field composed of boulders of the Weverton quartzite. The feature is approximately 0.70 mile long and 80-130 feet wide. The boulder field was formed by intense weathering and erosion during the “Ice Age.” These boulders were once part of large outcrops of the Cambrian-age quartzite (metamorphosed sandstone) which got broken into boulders and brought down the valley. A stream can still be heard running under the boulders.

Stop 2. Panning for Gold East Branch of Antietam Creek (need permission) Washington County Solid Waste and Recycling, Bikle Road in Smithsburg, MD. The art of panning for gold has intrigued humans for many years. Since the discovery of gold near Charlotte, NC in 1803 which led to the first commercial gold mine in the United States to the gold rush at Sutter’s Mill, CA, people always get excited when they hear “gold.” Although the author has never panned for gold in this vicinity, you can still learn the how’s and why’s in this short stop. The East Branch of the Antietam Creek flow off of the west side of South Mountain and actually originates within the Catoctin Formation metabasalt. Gold, like copper, forms within volcanic rocks. However, with my experience as well as other recreational panners, gold within South Mountain in Pennsylvania appears to be almost non-existent. It appears that gold within the Catoctin Formation is not very common. The area of our panning is underlain by the Cambrian Tomstown Formation, composed entirely of limestone. You will be instructed here on how to fill your gold pan with sediment and using the water, have the heavy minerals settle to the bottom of the pan and the other “junk” rock washed out of the pan. Heavy minerals would include magnetite (black sand), garnet and possibly gold. We will supply you with a small container if you would like to take your “heavy” minerals home for a souvenir or closer look. History of Gold in Maryland: The following is taken from “Gold in Maryland written by Karen Kuff (1987) published by the Maryland Geologic Survey. Maps and more information can be obtained at http://www.mgs.md.gov/esic/brochures/gold.html “Although gold was first reported in 1849 on Samuel Ellicott’s farm near Brookville, Montgomery County, no production was recorded. There are numerous versions of the first discovery of gold in the Potomac area. In 1861 during the Civil War, a Private McCleary (or McCarey) of the 71st Pennsylvania Regiment (or “1st California Volunteers”) was stationed outside of Washington, D.C. While encamped in the vicinity of Great Falls, he discovered gold. It is reported that the gold was found while washing skillets in a stream near McCleary’s hilltop camp overlooking the old Anglers Club. By 1867 the first shaft was sunk near the site of the Maryland Mine.” “Gold has been mined, panned or prospected intermittently since that date. Active mining ended prior to World War II in 1940 and the last recorded production from prospecting was 21 ounces found between 1950-51. The accompanying graph shows gold production in Maryland from 1868 to 1940. Prospecting continues even today. There is a surge of gold panning interest every few years, especially following an increase in the price of gold.“ “No great fortunes were made by Maryland gold miners. In 1890, Emmons stated that there was little likelihood of any new ventures that would result in sure riches for the operator.“ “On all of this belt …there is no record of any great mine the product of which can compare with the few enormously productive mines…in the west, and there seems to have been a very large proportion of disastrous failures among the many gold mining enterprises that have been undertaken here. There is some reason to assume that many of these failures have been due to ignorance and bad methods of working…the depth to which the rocks have been rotted and decomposed…has tended to make the surface showing underly rich; and has been an important factor in preventing systematic and successful mining in depth.” “Not all gold was obtained as ore from mine shafts; much was found by prospecting with trenches, or panning in local streams. The area around Great Falls has yielded most of the gold found in Maryland. Individuals hoping to find gold in Maryland are still looking in this area. Gold recovered by panning is mostly very fine grained but can range up to coarse sand size. Rarely, nuggets were found, some weighing as much as 4 ounces.”

Gold on top and magnetite on bottom of pan

Gold on top and magnetite on bottom of pan

Stop 3 George Washington State Park, Alt. Rte. 40 Boonesboro, MD Monument (Milk Bottle) composed of Weverton Quartzite If you have or never visited this first monument constructed in honor of our first President of the United States, it is always worth a visit. Each time you walk the short trail up to the monument you see something different. Closely examine the quartzite that composes the monument and enjoy the scenic view from the top of South Mountain. New landmarks are seen every time. Quartzite is a metamorphic rock, once a sandstone that has undergone heat and pressure associated with crustal collisions. The rock did not change chemically, but only texturally. Quartz is still the dominate mineral in the rock. Quartzite is coarser-grained due to the grains welding themselves together to make a larger quartz grain. The rock is hard (7.0 on the Moh’s Hardness Scale). Walking up the trail, float of quartzite are lying all over the ground. Examining the rock in the monument you can trace some indication of bedding. No fossils are present. Also, use your keen eye to pick up several quartzite blocks that appear to have 2 directions of bedding (layering) in the rock. This is known as cross-bedding which represents two directions of wave action at a beach when the rock was beginning to form as sandstone. The Weverton quartzite was used in many of the area’s historical buildings. Because of its durability and blocky shape, it is considered a long-lasting stone for buildings. Although rather hard to cut, the rock would be pretty polished after being cut. Ever wonder where the rock came from when you view a historic building? Chances are that the rock originated close by and hard by horse and wagon. For example, in the case of the Washington Monument, the rock came from right here. As we exit the park and return to Alt. Rte. 40, check out the church on the left side just before we travel down off of South Mountain. From the overlook, you are able to see at least 38 miles. Sidling Hill located on Interstate 68 west of Hancock appears as a notch in the mountain to the west. This section is known as the Valley and Ridge Providence or also called the Appalachian Mountains. This famous mountain range is composed of sedimentary rocks such as limestone, sandstone and shale ranging in age from Ordovician to Pennsylvanian. The wide valley below us is the Great Valley Section of the Valley and Ridge. The reason it is a valley is because the rock is mostly limestone and dolomite with some shale beds. Limestone and dolomite are rather soft, not holding up to the elements of weathering and erosion well, thus underlying valleys. Check out the framed photographs of the scenery on top of the tower which has landmarks indicated.

View looking west from Washington State Park

View looking west from Washington State Park

Point of Interest C Middletown Gneiss Exposure on MD Rte. 17 east of the Catoctin Creek, south of Middletown, MD With time restraints we are not able to show you this roadcut, but we have supplied enough samples for everyone to take home probably the oldest sample you have collected. This rock is known as gneiss, a metamorphic rock that illustrates to geologists just how intense the heat and pressure can become during a metamorphism event. This rock underlies much of the Middletown Valley, but exposures are rather obscure. The gneiss was originally a piece of a granitic crust making up a part of an ancient supercontinent known as Rodinia. The rock has been dated at about 1 billion years old. The rock was later involved in the pulling apart of Rodinia, the collision of a volcanic island arc to the east and the great African-North American collision to form Pangaea. Only if the rock could talk, what a story it could tell!! Gneiss is the highest grade metamorphic rock known. If the rock would have had more heat and/or pressure added, the material may have returned back into magma. When the rock was undergoing metamorphism, the white-colored minerals grouped themselves in a zone and the dark colored minerals gathered into their own zone, giving the gneiss a banded appearance. This rock is also believed to be the oldest rock found deep within South mountain and Catoctin Mountain in Maryland. Enjoy your gneiss!!

Point of Interest D Limonite (Goethite) from an area iron mine Again, because of time restraints, we will supply you with a sample of limonite, a.k.a. goethite. This ore was removed from a number of 19th century iron mines in this region and used in nearby furnaces to manufacture iron. We will see one of those furnaces at our last stop. Most of the mines were open pit, not requiring deep shafts to extract the ore. Much of the ore was laying loose in the clay which only required it to be washed and not removed from bedrock. Pick and shovel were about the only required tools. Horse and wagon removed the ore to its processing station or transported it to the furnace. Where blasting was required to dig into the bedrock, dynamite was not used commercially until 1890. Black powder was the main way to loosen the rock prior to 1980. Be careful, your hands will get dirty handling the limonite.

Stop 4 “Potomac Marble” exposure on Ballenger Creek Pike near the Substation 1.17 north of Points of Rock Road Rock Type: Breccia (Sedimentary) but known as a Fanglomerate due to its origin Age: Triassic Period With my experience of regional geology in southeastern Pennsylvania and now into Frederick County, Maryland, This is the nicest exposure of this rock that I know of. I read about this exposure in a book on Frederick County and Richard Gottfreid, professor geology at Frederick Community College suggested this stop. I have seen the fanglomerate quarried, sawed and polished from a farm in Lancaster County, Pennsylvania and wow, is it ever a pretty rock? Imagine that, seeing the large limestone angular boulders set in a reddish clay matrix, glued together. Yes, the rock has been used in several locations as an ornamental stone. The most famous is for pillars inside the National Capitol in Washington, D.C. I am sure there are smaller uses for the rock such as coffee table tops, chair molding in a room or around a fireplace. Just how did this rock form? The rock is considered Triassic in age. During this time, the area was located at about the same latitude as Miami, FL. The climate was tropical with abundant rainfall. It was also the time that the supercontinent Pangaea was beginning to split apart into the world as we know it. We are standing in what was a rift valley, similar to today’s example of the Red Sea. Land to our west was trying to go with North America and the crust to the east was going with Africa. The land here was sinking during the rifting and the valley walls were very steep. As streams flowed from the east into the rift valley, the streams had plenty of velocity coming down the valley slope and were able to carry larger rock fragments. Once the stream flowed out onto the valley floor, the stream’s velocity dramatically slowed and was forced to drop all of the boulders of limestone. As boulders were deposited on top of older boulder layers, as viewed from the air, the sediment appeared as a fan shape, thus known as an alluvial fan. In a dictionary, the rock would be classified as a breccia (rock containing angular fragments). Since we know the specific origin of the rock as an alluvial fan, the rock is known as a fanglomerate. Notice how the limestone is slightly more resistant to weathering and erosion than the reddish clay. The boulders are a little higher off of the surface. Let’s see who can find the largest limestone boulder!! It is hard to determine any bedding in the rock since the deposition was massive. The fanglomerate is estimated to be about 200 feet thick and exposures are localized. You will see the rock lying on the surface more often than in actual outcrops. Another factor is that these alluvial fans were not continuous along the end of a rift basin, but were spotty. It was reported by the Fredrick County School District website dealing with a geologic guide of the county that fanglomerate was encountered and dug out when the Pier 1 store along U.S. Route 40 was constructed in the last several years.

A pillar inside the National Capitol building in Washington, DC compsed of fanglomerate

A pillar inside the National Capitol building in Washington, DC compsed of fanglomerate

Stop 5 Vulcan Materials Quarry – Buckeystown Pike north of Buckeystown (need permission) Frederick formation – limestone – Cambrian age Grove formation – Limestone – Late Cambrian to Early Ordovican Our second quarry of the day is operated by Vulcan Materials Company. According to their website, here is an introduction to Vulcan Materials: “Vulcan Materials Company is the nation’s largest producer of construction aggregates—primarily crushed stone, sand and gravel—and a major producer of aggregates-based construction materials including asphalt and ready-mixed concrete. Our coast-to-coast footprint and strategic distribution network align with and serve the nation’s growth centers. We are headquartered in Birmingham, Alabama.” “Over 300 Vulcan sites produce construction aggregates, and about 200 facilities produce asphalt and/or concrete, which also consume aggregates. All of these are located in the U.S. except for our large quarry and marine terminal on Mexico’s Yucatán Peninsula. The products from this facility are primarily exported by ship to the U.S. Gulf Coast, where quality stone cannot be mined locally For more information on this company go to www.vulcanmaterials.com.” “What we produce is used in nearly all forms of construction. In particular, large quantities of aggregates are used to build and repair valuable infrastructure such as roads, bridges, waterworks and ports, and to construct buildings both residential and nonresidential, such as manufacturing facilities, office buildings, schools, hospitals and churches.” Here the limestone is used primarily for aggregate purposes, for asphalt roads, concrete roads, road base, lightweight block, rip-rap for slope stabilization, stone driveways, construction, etc. The basics of the operation is laying out blasts or shots, blasting rock, loading rock into haul trucks to take to the plant where the various rocks are crushed, screened, and separted into their appropriate sizes. Of course, knowing the geology and having a good mine plan are also important. At one time the rock was mined for use to make cement, however the chemistry is not quite high enough in calcium carbonate as Essroc like so they don’t get rock for that purpose any longer. Some customers use the rock for out of spec AG lime. Two limestone formations occur in this area. The Frederick formation is found within the quarry while the Grove formation lies to the east. Based on stratigraphy of these formations, each limestone unit can be divided further into members. From west to east, they are: Rocky Springs Station member, Adamstown member and Lime Kiln member, all belonging to the Frederick formation. The Grove formation can be divided into the Ceversville member and the Fountain member (west to east). You will be permitted to collect off of a pile of limestone here. Watch for white, yellow or other colors in veins or crystals. This will be calcite, the primary mineral that composed limestone. It has a hardness of 3 on the Moh’s Hardness Scale, has 3 directions or cleavage and forms rhombohedra or dog-tooth shaped crystals. Calcite will react with vinegar with made into a powder or more readily with muriatic acid.

Aerial geologic map of the Buckeystown quarry

Aerial geologic map of the Buckeystown quarry

Stop 6 Catoctin (Isabella) Furnace in Cunnigham Falls State Park near Thurmont 18th and 19th century iron furnace The historical marker states: ”Catoctin Furnace: An important iron furnace during the Revolution owned by Governor Thomas Johnson and his brothers. Furnished 100 tons of shells used at Yorktowne.” The Johnson Furnace was a cold-blast operation. It operated from 1776 to 1795, and then was idle until 1803. The furnace operated again between 1803 and 1811 with substantial improvements. Early production consisted of household implements, tools, cast iron stoves, etc. The works were purchased by by John Brien in 1831 and modernized. The furnace operated until it was shut down and dismantled in 1880. The site of the Johnson stack was probably in about the middle of the retaining wall behind the existing (Isabella) stack. Another owner built the Isabella Furnace in 1856. Both the Johnson and Isabella stacks were 33 feet high, but the Isabella was supplied with a steam-powered hot blast mechanism. The Isabella operation was a advanced design for a charcoal furnace. It might have been capable to use anthracite or coke, but neither were available. The Isabella is the remaining stack on display. A third stack, the Deborah, was built in 1873 about 140 feet south of the Isabella. It was a water or steam-powered hot-blast furnace which used coke or coal with a daily capacity of 35 tons of pig iron. It operated until 1903 and was then dismantled. In the late 1800’s, when the complex was at its heyday it consisted of: 80 houses for workers, a saw mill, a grist mill, a company store, farms, an ore railroad and 3 furnace stacks. Production was 9,000 tons of pig-iron annually. A magnetite (iron) mine was located on a hill to the southwest and continued to mine until 1912. Today, we should have time to visit the stack area and walk east to see the remains of the ironmaster’s house. Further walking on the trail will take you past slag heaps a raceway and dam for the waterwheel for the Johnson furnace.

Portal of the Catoctin Furnace

Portal of the Catoctin Furnace

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