Many of us have often wondered if geology careers were possible. Geology is so interesting… but could it be a career? Here are eight geology careers that can provide a good living and fulfilling work.

1. Museums

Museum jobs are increasing by an amazing 12 percent each year as projected over the years 2021-2031 by the U.S. Bureau of Labor Statistics. Most require a master’s degree and the median annual salary for a curator was $50,100 according to May 2021 data. Johns Hopkins University offers degrees in museum studies.

2. Environmental Geology Careers

Environmental geology careers are growing in prevalence in many countries. Have you ever driven past a service station where a tank was being pulled out of the ground and the tank and surrounding soils were being tested and removed/replaced as needed? Did you know a geologist put together the plan for testing the soil and groundwater and determining the best strategies for remediation? The environmental geologist career is high-paying, sometimes six figures per year.

3. Geomorphologist

Geomorphologists are in demand in government and private companies. Their work focuses on understanding how landforms change over time. They perform hydraulic, hydrologic and geomorphic analyses to map resources such as groundwater and petroleum. If you love math and geology, geomorphology could be a perfect match. The career pays well too!

4. Hydrographic Surveyors

Hydrographic surveyors use instrumentation to map out the shape, contours and depth of streams, lakes, inlets and ocean bottoms. They often work for government agencies or private companies doing surveys for the government and nonprofits. For example, ecological restoration of channelized streams requires a hydrographic surveyor to determine the best approach to restoration. The median salary is around $80,000 per year.

5. Gemologist

When we buy a diamond or any precious colored stone from a fine jeweler, a gemologist was responsible for identifying, grading and selecting it. Careers include working as a lapidarist, bench jeweler, consignment director, appraiser, jewelry litigation expert witness, a fine jewelry polisher, and a precious metal tester. A college degree in geology is not necessary to get started gem cutting. There are many gemology schools with programs and diplomas.

6. Mineralogist

Mineralogists collect core logs, conduct geochemical and geophysical surveying, create geological mapping, and examine geochemical samples like petroleum, minerals or rocks using such instruments as gas chromatographs, carbon analyzers, microscopes and spectrometers. They perform original scientific research to determine the ages and other characteristics of specific soils, minerals and rocks. They oversee processes that separate minerals from their ores. The educational requirement for most mineralogist jobs is usually a master’s degree at minimum.

7. Mud Logger

Mud loggers analyze drilling fluids after they have been drilled up. They analyze the fluids in a laboratory. Mud loggers determine the position of hydrocarbons to depth. They also monitor natural gas and identify the physical characteristics of outcrops available in a given area of study.

8. Wellsite Geologist

Wellsite geologists are the next level up from mud loggers and you must be a mud logger first. Both require a bachelor’s degree in geology. Wellsite geologists classify rock cuttings removed from wells. They use rock-cutting data, core samples and specialized tests to advise gas and oil operators on how deep to drill wells. They prepare reports during and after the drilling. This is one of the highest-paying geology jobs with salaries topping six figures per year.

Geology Careers Provide Varied Work

The pay can be good. But geology careers are not just about making money. It’s also the wide variety of work and the demand for it. The Bureau of Labor Statistics projects a 4.5 percent job growth in the geosciences, including environmental geoscientists, from 2021 to 2033, a 5 percent job growth in geoscientists, not including hydrologists, overall, and a 5.4 percent job growth increase in geoscience technicians.

Consulting Geology Careers

Dennis Papa, P.E. is a principal at dpSTU-DIO LLC, Environmental Consulting and Design with offices in Richmond, Virginia and Providence, Rhode Island.

“Back in the late 1980s (seems like the Precambrian!) many undergraduate geology programs were focused on petroleum exploration and mineral resources. That is what I was originally interested in, imagining a career looking for oil-bearing formations. When jobs in petroleum and coal exploration started to become scarce, the environmental industry was just ramping up. I was drawn to the idea of a job that offered a mix of both fieldwork (doing well installation, groundwater and soil sampling) as well as office work to write reports, use software, and engage with other experts and clients to study a contamination problem.”

Many wonder if a professional geologist license is needed. “The P.G. is simply a test that each state offers to a geologist who has the requisite degree and minimum years working in the industry. A national exam is now offered to standardize the test. but not all states require it. Many states require a P.G., or working directly under a P.G., to practice geology, but it is not a requirement for all careers in geology and is certainly not required once starting out.”

Geology Tools & More…

As with any job, sometimes the fun is in the tools used. “Tools always offer that tangible connection to your trade. The geologist hammer is indispensable. A hand lens magnifier, soil color chart, and grain size chart used to compare sorting, size, etc. of sediment and rock samples are important tools to help provide useful data in standardized terms. Aerial photographs are used. We also routinely use a water level meter to accurately measure depth to water level.”

Dennis works closely with other specialists. “We rely very heavily on experienced and licensed well drillers, geotechnical engineers, wetland scientists, soil scientists, archeologists and geophysicists.”

In Dennis’ opinion, “I am partial to the environmental consulting field because it has offered me so much. However, I think there are so many geology career paths to choose from, and there have been so many advances in the subspecialties, that it just depends on your particular interests. Some offer more time in the field, others more opportunity to work in an office or laboratory. And if you can’t decide, the beauty is that many geology jobs offer a combination of both.”

Geologist

Claire Starke is a geologist with a large consulting firm with offices around the world.“I knew I wanted to be a geologist at age seven and I chose environmental geology because I felt that it would get me further in the business world and encompass different types of jobs. I graduated in the spring of 2021 so I was going to school through a time when environmental remediation and sustainability was a large chapter covered in all my major classes.”

A typical field day for Claire includes, “I mainly work with environmental sampling in groundwater monitoring wells. I use different types of well pumps to pull the water out of the well at a low flow rate. We work with drilling companies, and they will do the physical placement, but a geologist will tell them where to put the well, how deep to drill, and how deep to place the screen of the well. I have worked with hydrologists and hydrogeologists to figure out groundwater flow. I have worked with chemists to discuss the chemicals found in groundwater samples.”

What geology fields are best? “In my opinion, environmental remediation is the best geology field for the time we are in now. There are always new chemicals being found to be dangerous to human health, someone is needed to address the issue and needed for remediation, so it’s a sustainable career because the job is never done. You get a very nice blend of field and office activities. You also get to make the world cleaner and healthier in small and big ways.”

This story about geology careers appeared in Rock & Gem magazine. Click here to subscribe. Story by Deborah Painter.

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Believe it or not, some geodes grow just that big! Brazilian amethyst vugs the size of small hot tubs have on display at the Quartzsite and Tuscon rock extravaganzas. But these are still babies compared to supersized cavities lined with supersized crystals.

Discovering the Pulpí Geode

One such geode has been dubbed the Geoda de Pulpí or the Pulpí Geode. This “Geoda Gigante” was discovered 165 feet underground in 1999, in an abandoned silver and lead mine in southeastern Spain’s Almería province. At 26 feet long by 6 feet wide by 5.5 feet high, it has been described as about the size and shape of those cement mixer drums mounted on trucks. Its total volume is estimated at 390 cubic feet. Its crystals, composed of ice-clear selenite, average a little over 1.5 feet in length although some are as long as six to seven feet!

Enjoy this popular YouTube video tour of Geoda de Pulpí, which is narrated in Spanish.

In a recent issue of the journal Geology, a team of earth scientists led by Juan Manuel García-Ruiz speculates how this and similar giant geodes grew. In this instance, it involved a cave-sized cavity, a lot of dissolved calcium and sulfate minerals in groundwater, and a long time for crystal growth. The sulfate minerals were likely provided courtesy of an event 5.5 million years ago when the entire Mediterranean Sea dried up.

Understanding Super-Sized Geodes

The big key to super-sized growth was temperature fluctuation related to climate at the time the crystals grew. The researchers have dated the crystal growth to a period two million to 60,000 years ago, or the Pleistocene Ice Ages. This epoch of Earth’s history saw repeated advances and retreats of glaciers as temperatures swung back and forth between icy cold and relative warmth.

There is a process of crystal formation referred to as “cannibal chemistry” or “Ostwald ripening.” In this process, small crystals dissolve and get sucked into ever bigger crystals in solution. Warm temperatures favor the dissolution of smaller crystals whereas chilly temps favor larger crystal growth. Thus the Pleistocene Epoch provided just the right conditions to favor “Ostwald ripening” and the creation of the massive Pulpí Geode.

Other scientists have noted, however, that climate fluctuations above ground may not significantly affect the subterranean environment, which is more likely to be influenced by subsurface hydrothermal activity. Still, climate change could have an effect in that warmer, wetter periods could provide more water to flood into subsurface cavities while colder, drier times would then allow for growth spurts for the selenite crystals.

However it came to be, the Pulpí Geode has surely earned its nickname of “Geoda Gigante”!

This story about super-sized geodes appeared in Rock & Gem magazine. Click here to subscribe Story by Jim Brace-Thompson.

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I was visiting family in Ohio, and they told me of a crystal cave up North located at a winery. The crystal cave is on Put-In-Bay Island in Lake Erie, where Paul Bunyan could have easily skipped a rock across the water border into Canada. A ferryboat over to the island takes vehicular traffic as well as walk-ons, and if you are going for the day, I highly recommend walking. Parking lots on the mainland and golf carts available for rent on the island make this an easy option.

History of the Crystal Cave

The crystal cave is at the Heineman’s Winery. Fortunately, it turns out that the wine-sipping part of the program comes after the cave and winery tours. In 1897, the winery owners were digging a well and broke through the top of a cave lined entirely with whiteish-blue crystals. They thought they had struck it rich, but they found strontium sulfate crystals, also known as celestite. They mined some of the cave’s interior to sell the material as an ingredient in fireworks but soon realized that the cave’s greatest value was a tourist attraction. During Prohibition, tours of the cave helped prevent the winery from going out of business.

The winery’s origins date to 1888 with founder German immigrant Gustav Heineman. The winery has been in the family since. They produce over 20 varieties of red, white, and dessert wines from local grapes. During our visit, upon entering the winery, we signed up for the next cave and winery tour, and the cost of $8 included the cave tour, winery tour, and a glass of wine or grape juice in the tasting room afterward.

Touring the Crystal Cave

As we assembled for the tour, 20 of us lined up to walk down a long flight of stairs into the cave, which is 40 feet below ground. Our group just filled the main chamber, and all were careful not to touch the sides. The delicate mineral growths in the cave cannot take being rubbed by endless groups of tourists.

While we made our way through the cave, I found myself on the edge of the main group in a side tunnel that circles back to the base of the stairs. I walked through this tunnel to get behind the group, and as they exited through the tunnel, I was able to take pictures that would show the cave and not a tight pack of 20 tourists.

The winery owners call the cave the largest Celestine geode in the world, and tours are offered from May through September. This tour is a wonderful experience for anyone who is able to walk downstairs and through a crystal-lined cave. After the cave tour, we toured through the winery, learned about the process and then went to the tasting room. I enjoyed their wine and went home with a bottle of their dessert ice wine. It is made from grapes picked after the winter frosts have set in, making a very sweet sipping wine.

Heading to Kelleys Island

We left Put-In-Bay, made the ferry crossing back to the mainland, and headed to the next ferry. This ferry took us to Kelleys Island, another Lake Erie Island barely south of the Canadian border. The goal of this excursion was to spend a couple of nights camping at Kelleys Island State Park. We had no idea we would end up having such a great time rockhounding throughout this island.

Exploring Glacial Grooves

We had read about the Pleistocene glacial grooves at the state park, the largest in the world, so we walked from our campsite to the closest of the grooves that still exist. Several large limestone quarries exist on the island, and some of the glacial grooves were destroyed by limestone mining. The groove at the park was only partially visible until the 1970s when it was excavated, fenced off from foot traffic, and an informative trail built to encircle it. This trail includes an area accessible to wheelchairs. The information posted at the groove tells how the glaciers slowly moving over the landscape ground the grooves into the limestone.

As I was looking at the surface of the groove, it looked to me to have been formed by flowing liquids, not rocks embedded in the bottom of a glacier grinding away at the limestone. Why was it such a deep groove? Why were the grooves flowing into each other instead of parallel grinding marks that I have seen from other glaciers? However, that is what the interpretive signs said, so I didn’t argue with the signs.

Alternative Glacial Grooves Theories

Later, when I met with the State Park Manager, Chris Ashley, he told me of another proposed theory, and it makes much more sense to me. Streams of high-pressure water have been observed shooting out of the base of glaciers. The weight of the glacier can create water that becomes liquid at temperatures lower than freezing. When this trapped water escapes the glacier, it shoots out at great speed, carrying with it the debris picked up by the glacier. I liken it to the water jet cutters used by steel and stone cutters, only loaded with rocks and sand for extra scouring power.

When looking at the groove’s interior, the water flow patterns fit this glacial groove-making theory better than the old grinding concept. I hope that any new interpretive signs will add this new theory.

Another discovery we made is that the limestone in this location is loaded with fossils from the Devonian Sea. As we walked around the groove trail, the rocks we walked on were pockmarked with coral, snails and other ocean fossils. Back at the park office, we were informed that any fossils that are loose are legal to keep. Leave your rock pick in your car, though, because it is not legal to mine fossils from the rocks, but you won’t mind because there are plenty of loose rocks containing fossils to pick up.

Crystals, Wine, and Fossils, Too

Fossils here include corals, brachiopods, gastropods, pelecypods, cephalopods, crinoids, and stomato-poroids, 18 different types of marine fossils. I wanted to find one of the nautilus-type shell fossils, so we went over to the large quarry on the island’s southern side. I had my nautilus shell within half an hour. The fossil I found was a little one, three inches in diameter, but nautilus fossils a foot in diameter have been found on the island.

The Park Manager also showed me a less common stone from Kelleys Island, which is tillite. This type of glacial erratic rock came down from a Gondwanan deposit north of Lake Huron. It is an approximately 2.5 billion-year-old stone formed when granite was broken up and later encased in a glacial till that formed into rock. I tried to find one but was unable.

An Art Gallery Visit

One last stop on our tour of Kelleys Island was the art gallery of Charles Herndon at 110 Laylin Lane. For over 30 years, Herndon was an art professor at Columbus College of Art and Design, and his stone sculpture gallery is outdoors and indoors. The gallery also features paintings and photographs, and much of his stone has come from Kelleys Island. A stone carver myself, I greatly admired his skill and sense of design with rock. The gallery is open to the public, and you shouldn’t miss it.

This story about exploring the crystal cave in Ohio appeared in the April 2021 issue of Rock & Gem magazine. Click here to subscribe! Story by Bruce McKay.

The post Exploring the Crystal Cave in Ohio first appeared on Rock & Gem Magazine.

Mining Guano

When discussing caverns in the United States, Mammoth Cave in Kentucky, Carlsbad Caverns in New Mexico, and Kartchner Caverns in Arizona share some similarities and exhibit major differences. For example, Mammoth Cave was mined for a mineral of destruction during the War of 1812, and Carlsbad was mined for minerals of growth and life.

Before the development of processes to manufacture fertilizers, the natural stuff was used. Behind every barn was the ever-present smelly pile of cow and horse manure to be spread on the land each spring during planting. World travelers found that other animal droppings, particularly that of flying creatures (not chickens), were another good option for the farmer. Bat guano was one such natural fertilizer. In regions where caves and their resident bats were known, mining bat guano developed into an important business for farmers. It provided a great off-season source of income to people who lived off the land.

Discovering Carlsbad Caverns

And so it was at the turn of the century when cowboy and guano miner Jim White decided to investigate a huge cavern from which hundreds of thousands of Mexican fruit bats issued each summer night. The bats fed on insects in the Pecos River Valley, migrating to Mexico each fall to return in late spring. (Remember this when you plan a visit to Carlsbad. The bats are in Mexico during winter).

One story about the discovery has it that Jim White was riding in the area around dusk one evening when he saw a huge black cloud rising from the hills. He thought it might be a fire, so he rode closer to investigate, only to discover a cave opening disgorging clouds of bats. More likely, he found out about the opening from some wandering local and determined to search it for guano.

Be that as it may, Jim discovered two important things in his investigation of the cave: stunningly beautiful cave formations and layers of guano, sometimes 30 or more feet deep on the cave floor. White did his best to convince people of the magnificence of what he found underground. But it took some time before the idea caught on. Soon Jim and a few others were taking people underground to see this breathtaking display of nature’s handiwork.

What to See in Carlsbad Caverns

Carlsbad’s spectacular formations today result from groundwater action dissolving and redepositing massive amounts of calcite limestone in the existing openings. It creates stalactites, stalagmites, travertine flows, and hosts of lesser but equally beautiful formations that far exceed what you will see in Mammoth Cave, where vastness is the prime attraction.

In Carlsbad, you can take several tours, most of which are relatively easy, some not. But none requires a hard hat, kneepads and such exertion as to leave you breathless.

Carlsbad Caverns Formation

Carlsbad formed somewhat differently from most scenic caves. The process that makes cave openings, including Carlsbad, is typical for limestone caves: the limestone’s dissolution by groundwaters. Yet, in Carlsbad, something special happened as these cave openings grew. There was a change in the dissolving ingredients — a dramatic change.

Generally, cave formations result from acidic waters containing carbon dioxide and organic matter, forming a weak carbonic acid. Water is, itself, a natural dissolver. But unless it is acidic, it works very slowly. Nature sees to it that the waters that seep underground are slightly acidic. As rain falls through the air, it absorbs minute quantities of carbon dioxide. When carbon dioxide reacts with water, it forms a very weak solution: carbonic acid. After it rains, this same, now slightly acidic groundwater absorbs organic matter from the soil as it works its way down to bedrock. This adds to its acidity.

Acidic Water Attacking Limestone

Bedrock in limestone country is anything but solid. Horizontal layers of limestone tend to develop cracks and joints — perfect avenues for this acidic water to reach deeper and deeper into the earth, dissolving away the limestone (impure calcite) as it goes. This creates the chambers, avenues, tunnels, and the like in the limestone. In many cases, the mineral-laden waters are drained away by underground streams. But there can also be the development of cave formations, depending on conditions in the cave or even in a particular cave opening.

If they are not carried away by flowing water, any opening encountered gives the water an opportunity to drop the mineral load, especially as the water evaporates. Thus, acidic groundwaters dissolve away the limestone, creating an opening that later groundwater may use as a dumping ground, depositing thin layer upon layer of calcite. If the water runs down the face of a cave opening, it creates solid “curtains” or “flows” that look like frozen waterfalls. These are sometimes called travertine falls. If water drips from a crack in the ceiling, it leaves behind a minuscule amount of calcite. This builds and builds to form stalactites. The water that drips to the floor also deposits calcite as it evaporates, building stalagmites. If the two should grow enough to connect, a column is created.

When Carlsbad was first studied, it was assumed that carbonic acid had been the key agent in the water that created this underground fairyland. Initially, this was true, as the groundwaters created the cavernous interior. But something happened on the way to modern times. Gas and oil deposits deep below the Carlsbad area began releasing gases, mainly hydrogen sulfide. As this poisonous and water-soluble gas rose toward the earth’s surface, it mixed with the down-trickling groundwater, forming a much more powerful dissolving acid. We call it battery acid! It is sulfuric acid, which is capable of dissolving the proverbial kitchen sink.

What happened here is virtually the same as what happens when sulfur-bearing ores decompose and release sulfur, often in the form of hydrogen sulfide. This chemical attacks the primary ores, creating a whole new, and more easily smelted, zone of secondary or oxidized ores. These oxidized ores near the surface of a metal vein are largely responsible for many of the beautiful minerals we collect. The ores are important to the early development of mining in this country, as oxidized ores could be smelted while sulfides could not ….until the development of chemical means of breaking down the sulfides.

Cave Formations in Carlsbad Caverns

Because Carlsbad’s waters were much more acidic than other caves, thanks to sulfuric acid, the limestone was attacked very vigorously. The resulting calcium carbonate-laden waters at Carlsbad provided the raw materials that created Carlsbad’s abundance of huge caverns that can be found in overwhelmingly beautiful cave formations.

A visit to the Big Room is evidence of that. The room covers 14 acres and is over 750 feet beneath the earth’s surface. It took several million years to create the cavern openings here, and another half-million to create the wonders you see on an easy hike underground.

An elevator brings you back to the surface so that even older folks and small children can revel in the wonders of Carlsbad. There is even a restaurant and gift shop below ground — so you can leave a little of your money in the cave, as well.

Guadalupe Mountains

Carlsbad is actually in the same limestone formations as the Guadalupe Mountains, which are composed of some of the extensive and significant members of the Permian limestones in the U.S. Permian rocks are the source of much oil and natural gas in Texas and elsewhere. Permian-age material formed just before the Age of Dinosaurs, some 200 million years ago.

The Guadalupe Mountains’ most impressive feature is Capital Reef, a high escarpment or cliff area where the land has been uplifted dramatically. The rocks that comprise the reef are fossil limestone, and one portion of it, El Capitan Cliff, rises over 1,000 feet above the surrounding parched land. A visit here is fascinating because of the early sea life fossils and the so dramatically different vegetation from the arid terrain surrounding it.

This story about Carlsbad Caverns previously appeared in Rock & Gem magazine. Click here to subscribe! Story by Bob Jones.

The post Exploring Carlsbad Caverns first appeared on Rock & Gem Magazine.

Each year, these remarkable landforms attract hundreds of millions of visitors. For those interested in geology, the time to visit the national parks and monuments has never been better, thanks to updated and upgraded geologic explanations.

Historically, geology had long taken a backseat to the parks’ more obvious attractions of scenery and wildlife. But in the 1950s and 1960s, growing numbers of visitors began showing interest in the earth sciences, especially geology. In the early 1990s, the National Park Service began rethinking the role of geology as an attraction. Since then, it has placed greater emphasis on geologic education—in other words, on the science behind the scenery.

Awe-Inspiring Geology

Today’s visitors still marvel at the landforms for which the national parks and monuments are famous. But now, more detailed exhibits, improved interpretive signage and focused ranger programs and lectures make it easier for visitors to learn.

The landforms in the national parks and monuments were created by five basic geologic processes: sandstone erosion, volcanics, groundwater dissolution and redeposition, glaciation and mountain building and faulting.

The Colorado Plateau

The Colorado Plateau, an elevated physiographic region that covers 130,000 square miles in the Southwest’s greater Four Corners region of Arizona, Utah, New Mexico, and Colorado, has the best examples of sandstone-erosion landforms.

The Laramide Orogeny, the tectonically driven uplift that created the Rocky Mountains some 70 million years ago, raised much of the Southwest more than two vertical miles to form the Colorado Plateau. This uplifting accelerated the rate of wind and water erosion across this vast expanse of brightly colored sedimentary rock to eventually create an array of canyons, cliffs, arches, pinnacles, and pedestals.

Grand Canyon National Park

The Colorado Plateau has nine geologically oriented national parks and monuments—the greatest concentration in the nation. Among them and heading the list is northern Arizona’s Grand Canyon National Park. The walls of the 277-mile-long, 18-mile wide, 6,000-foot-deep Grand Canyon expose 40 major sedimentary strata from the four major eras in the Earth’s evolutionary sequence: Precambrian, Paleozoic, Mesozoic and Cenozoic.

Ranging in age from 200 million years to 1.9 billion years, these rocks represent the longest exposed span of geologic time on Earth. Yet the canyon itself, which formed after many rivers had consolidated into the Colorado River, is a mere six million years old.

Visitor centers on both the park’s north and south rims provide detailed explanations of the canyon’s origin and complex stratigraphy. Virtually every type of geologic feature within the canyon is visible from the South Rim’s Yavapai Geology Museum, which also marks the start of the 1.3-mile-long Trail of Time. This interpretive walking tour, designed so that each meter of travel represents one million years, helps visitors to grasp the magnitude of geologic time.

Petrified Forest National Park

Also in northern Arizona is Petrified Forest National Park, a barren landscape of mesas, gullies, and buttes that exposes thousands of 225-million-year-old petrified logs and the brightly colored Triassic Period strata of the aptly named Painted Desert.

Fascinating Formations

Near Moab, Utah, Arches National Park protects the world’s greatest concentration of natural arches—more than 2,000, including 306-foot-long Landscape Arch, the longest arch in North America; 112-foot-high Double Arch; and 45-foot-high Delicate Arch, one of the National Park Service’s iconic symbols.

Millions of years ago, winding watercourses in what is now the park had undercut deep “potholes” at the base of numerous cliffs. As erosion reduced the overall surface, these undercut cliffs were transformed into the park’s celebrated arches, a lengthy and complex process that is explained in educational exhibits. Arches National Park also has many red-and-yellow sandstone pinnacles, including Balanced Rock, a thin spire atop which is a precariously balanced 3,500-ton sandstone boulder.

In his book Desert Solitaire, author Ed Abbey described the vast mazes of canyons and buttes in nearby Canyonlands National Park as the “most weird, wonderful and magical place on Earth.” The Colorado and Green rivers divide this park into the Maze, Islands in the Sky, and Needles districts, each with unique, dramatic landforms that water has carved from 300-million-year-old sandstone.

Southern Utah’s Bryce Canyon National Park and Cedar Breaks National Monument feature thousands of brightly colored stone pinnacles, spires, pedestals, and thin columns called hoodoos. These features were created when sandstone formations developed vertical joints (fractures) during the stress of regional uplifting. Water then seeped into these joints and, in a process called “frost wedging,” froze, expanded, and separated them.

Tall, thin spires eventually formed wherever hard caprock protected the underlying rock from further erosion. The spires’ bright red, orange, yellow, and purple colors are due to the presence of iron and manganese oxides within the sandstone.

Although not on the Colorado Plateau, South Dakota’s Badlands National Park is another extraordinary example of sandstone erosion, a process that continues today. Sections of this expanse of deep gullies, sheer slopes, and sharp ridges lose a half-foot of surface material each year—one of the world’s highest erosion rates.

One of the many parks and monuments that showcase volcanic landforms is Wyoming’s Yellowstone National Park, the site of the Yellowstone Caldera, a collapsed volcano that is part of North America’s largest volcanic system. Sections of the park lie atop a 37-mile-long, 18-mile-wide magma chamber that in places is only 3 miles deep. Known as the Yellowstone Hot Spot, this plume of magma that has risen high into the Earth’s crust is the heat source for the park’s 10,000 geothermal features. These include erupting geysers, brilliantly colored hot springs, steaming fumaroles, and bubbling mud pots.

In recent geologic time, Yellowstone has hosted three catastrophic volcanic eruptions. The most recent, though not catastrophic, occurred just 77,000 years ago and was far larger than any eruption witnessed in historic times.

A 270-mile-long succession of calderas extending from Yellowstone west into Idaho and Oregon formed over a period of 17 million years as the North American tectonic plate drifted westward over the geologically stable Yellowstone Hot Spot. This succession of calderas was created at the rate of 15 miles per one million years—precisely matching the tectonic-drift rate of the North American Plate.

The maze of lava flows, cinder cones, vents, fissures, and tubes (caves) in southern Idaho’s Craters of the Moon National Monument and Preserve marks the position on the North American Plate that overlaid the Yellowstone Hot Spot 10 million years ago.

At Oregon’s Crater Lake National Park, the beautiful, 21-square-mile Crater Lake formed 7,700 years ago after the Mount Mazama volcanic system erupted, then subsequently collapsed. The resulting caldera later filled with rainwater and snowmelt to become 1,949-foot-deep Crater Lake, the nation’s deepest lake.

Six volcanoes in southern Alaska’s Katmai National Park and Preserve have erupted in historic time and seven others in recent geologic time. This park was established following the simultaneous 1912 eruptions of two volcanoes: Mount Katmai, which formed a crater lake, and Novarupta, which created the Valley of Ten Thousand Smokes with its countless, still-steaming fissures and fumaroles.

To observe the effects of very recent or even current volcanic activity, the place to go is Hawaii Volcanoes National Park on the island of Hawaii. Among the park’s volcanoes are 4,091-foot-high Kilauea, the world’s most active volcano, which last erupted in 2018, and 13,679-foot-high Mauna Loa, the world’s largest shield volcano.

Captivated by Caves

The 4,700 documented caves scattered throughout the national parks and monuments are classified into four types. Lava caves or tubes are conduits in lava flows; talus caves are open spaces beneath mountain talus slopes. Sea or littoral caves are carved by wave action, while large and often spectacular solution caves are created by the dissolution of limestone and dolomite bedrock.

Solution caves originate when groundwater dissolves the calcium carbonate in limestone and the calcium magnesium carbonate in dolomite rock to create subterranean tunnels, chambers, and galleries. Later redeposition of dissolved carbonate minerals created such decorative cave formations as drapery-like flowstones, icicle-shaped stalactites, spire-like stalagmites, columns connecting floors with ceilings, and twisted growths called helicitites.

Mammoth Cave in Kentucky’s Mammoth Cave National Park is the world’s largest limestone cave and contains more than 300 miles of explored passageways. Wind Cave in South Dakota’s Wind Cave National Park, the world’s eighth-largest limestone cave, is known for its glittering “boxwork” calcite crystals. At Carlsbad Caverns in New Mexico’s Carlsbad Caverns National Park, the world’s largest underground galleries are adorned with an unusual diversity of cave formations.

Glaciers and Glaciated Landscapes

Another geologic attraction in the parks and monuments are glaciers and glaciated landscapes. At Minnesota’s Voyageur National Park, the scouring of continental glaciers has uncovered 2.1-billion-year-old Precambrian rocks—North America’s oldest exposed rocks. The topography of Michigan’s Isle Royal National Park, an island in Lake Superior, consists of long parallel ridges, lakes, and bogs that Pleistocene continental glaciers carved from granite bedrock. At Acadia National Park, located largely on Maine’s Mount Desert Island, continental glaciers have left behind rounded granite hills that border a rockbound coast.

The effects of regional (alpine and valley) glaciation—deep valleys, rounded granite domes, and the sheer, half-mile-high rock faces of the imposing El Capitan and Half Dome monoliths—await visitors at California’s Yosemite National Park. El Capitan and Half Dome are textbook examples of roche moutonnée features. On their up glacier sides, these masses of bedrock are gently inclined and rounded. But on their down glacier sides, Pleistocene ice sheets have scoured away jointed granite. This has left sheer cliffs and such famed waterfalls as 2,425-foot-high Yosemite Falls and 1,612-foot-high Ribbon Falls.

At Washington’s North Cascades National Park, more than 300 valley, alpine, and cirque glaciers represent the largest concentration of active glaciers in the lower 48 states. The park’s ranges of high, jagged peaks are characterized by deep glacial troughs, glacially dissected uplands, and numerous roche moutonnée features.

Southern Alaska’s Glacier Bay National Park and Preserve is the site of more than 1,000 tidewater and terrestrial glaciers. There are broad ice fields, creviced glacial termini, calving glaciers and glaciated landscapes. Heavy rainfall and snowfall constantly replenish these glaciers, making this park an ideal field laboratory to study glacial advances and retreats.

Mountain Building

Mountain building and faulting created California’s Death Valley National Park’s dramatic, barren landscape of playas, sprawling alluvial fans, young volcanic craters, sand dunes and narrow canyons. The floor of Death Valley, elevation 282 feet below sea level, is North America’s lowest point—yet 11,000-foot-high summits within the park are only 12 miles distant.

With six major geologic faults, Death Valley is a rift valley that formed when long blocks of crust slowly subsided between parallel fault systems. Fault displacement of more than 10,000 vertical feet accounts for the park’s wildly varying elevations. Surface traces of faults and their associated steep escarpments are clearly visible at several points within the park.

At Wyoming’s Grand Teton National Park, extremely old rocks are exposed on some of the continent’s youngest mountains. Just 10 million years old, the Grand Tetons are much younger than the main chain of the Rocky Mountains. They continue to uplift along the active, 40-mile-long Teton Fault. This fault displaces about one foot every 300 years, meaning that the valley floor is still sinking while the Tetons continue to rise.

Many lesser-known parks and monuments also have fascinating geologic attractions. Among these are the following.

• The symmetrical volcanic cinder cone at New Mexico’s Capulin National Monument and the snow-white gypsum dunes at White Sands National Park.
• Rhyolite-tuff pillars at Arizona’s Chiricahua National Monument.
• The intricate maze of lava-tube caves at California’s Lava Beds National Monument.
• The recovering volcanic landscape left by the 1980 eruption of Mt. St. Helens at Washington’s Mt. St. Helens National Volcanic Monument.
• The 1,200-foot-high volcanic neck at Wyoming’s Devils Tower National Monument, the latter an iconic image in the 1977 movie “Close Encounters of the Third Kind.”

With a few dramatic exceptions of ongoing volcanism, glacial movement, and rapid erosion, along with the occasional collapse of spires and arches, the parks’ geologic features have changed relatively little since the first parks were established in the late 19th century. Since then, however, the understanding of geology and geologic processes has advanced considerably.

Showcasing Geology

For many decades, the National Park Service had adhered to outdated ideas in its presentations of park geology. It continued to emphasize scenery and wildlife while focusing attention on visitor services rather than visitor education. But by 1990, the National Park Service realized that its geologic presentations had fallen well behind scientific advancements.

In 1995, the National Park Service established its Geologic Resources Division, a branch charged with inventorying the parks’ geologic resources; improving visitor safety regarding geologic features; preparing geologic training manuals for park rangers who guide visitors; monitoring and measuring geologic changes within the parks, and monitoring mining and other activities in areas adjacent to the parks.

Today, the National Park Service’s Geologic Resources Division employs 30 geologists. One of their most important jobs is upgrading the parks’ educational exhibits, signage and presentations.

Along with the world’s most magnificent rock collection, the national parks have also been called the world’s greatest set of outdoor classrooms. Geology courses at numerous colleges and universities rely heavily on field trips. The national parks are a favorite destination.

But anyone can transform a visit to the national parks and monuments into an exciting and educational geology field trip. All that’s needed is to remember to take full advantage of the visitor centers and educational centers. They bring the parks’ geology to life through updated and improved ranger programs, exhibits, and interpretive displays.

An excellent primer to national park field trips is Geology of the National Parks (2020, Kendall/Hunt Publishing Company, Dubuque, Iowa) by David Foster, David Hacker, and Ann Harris. Both formats have hundreds of excellent photographs and maps, as well as a dedicated chapter for each of 59 geologically oriented national parks. While the 2020 edition is an excellent reference, it is not inexpensive; the hardbound 6th edition (2004) is more affordable and still widely available.

Now that geology has come of age in the National Park System, there’s no better time to enjoy the parks’ remarkable beauty, vistas, and landforms, and to learn about the science behind the scenery.

For information about the national parks and monuments, visit www.nps.gov.

This story about geology in the National Parks previously appeared in Rock & Gem magazine. Click here to subscribe! Story by Steve Voynick.

The post Geology in the National Parks first appeared on Rock & Gem Magazine.

Per a recent article in the journal Science, Mount Nyiragongo in the Democratic Republic of the Congo refuses to leave the headlines. The volcano—considered one of the most dangerous in all of Africa, if not the entire world—burst forth in a deadly eruption on May 22, 2021. As the eruption and lava flow continued, it killed more than 30 people, destroyed thousands of homes, and prompted the evacuation of some 400,000 Congolese citizens.

Blame quickly was placed on government officials who, it is said, decommissioned a volcano monitoring station (Goma Volcano Observatory, GVO) due to lack of funds as a result of the COVID-19 pandemic. However, officials in the Democratic Republic of the Congo blame a “European data monopoly” for hampering efforts that could have saved lives.

Per the article in Science, European partners in the GVO are being accused of “a ‘neocolonial’ attitude” in data sharing prior to the eruption. The accusations were made on behalf of local Congolese staff researchers and technicians. They say they have long been shut out of decision-making due to corruption and squandered financing, both within their own government and on the part of European partners. They also point to “turf protection” by those European partners. They blame all this for the failure to monitor an imminent and deadly geohazard that could otherwise have been forecasted with confidence.

Accusations of one sort or another are now being flung back-and-forth. But when it comes to one of the most deadly volcanoes on Earth, one would hope that politics and “turf” might be put aside in advancing the safety and security of our vulnerable fellow citizens here on planet Earth. At least, that is the hope of this humble reporter.

The post Questions Linger After the Deadly Eruption of Mount Nyiragongo first appeared on Rock & Gem Magazine.

We are very excited that after more than a year of canceling three EFLMS Wildacres Workshops due to COVID-19, finally the EFLMS Wildacres Workshop will be back this fall. It will be held September 6-12, 2021. The Wildacres Workshop takes place in the beautiful mountains of North Carolina, near Asheville. The workshop is sponsored by the Eastern Federation of Mineralogical Lapidary Societies. For information and registration, please visit www.efmls.org/wildacres/.

Besides the hands-on workshops, at every session a Speaker-in-Residence gives six lecture presentations. As the coordinator for the speakers, I am very happy to share that this fall the Speaker-in-Residence will be Wolfgang Mueller.

Wolfgang is a retired geologist, mineral collector, and a very active lapidary. He has rockhounded in many places around the country and is famous for his hand-cut spheres and eggs, as well as rare gem material cabochons and one-of-a-kind beads. His talks range from mineral collecting to lapidary. He has a wealth of knowledge, which he is always happy to share. He received a top prize best-of-class award at the 2019 Tucson Gem & Mineral Show for his self-collected wulfenite specimen exhibited in a in a competitive case exhibit.

Wolfgang was born in 1942 in the same town (Belgrade) as the person for whom Wulfenite is named – Franz Wulfen, a Jesuit born in 1725. He has a Bachelors and Masters degree in geology from the University of California in Riverside. He worked at Magma Copper in San Manuel and their corporate entity, Newmont Exploration, in Danbury, Connecticut. Wolfgang moved back to Arizona, to Oracle, some 22 years ago and loves going out rockhounding and collecting minerals. He can still swing a 20lb sledgehammer!

Wolfgang will be accompanied at Wildacres by his wife, Diana, who is also a lapidary and jewelry artist. Together, they are the lapidary and jewelry forces behind their company DiWolf, exhibiting at several gem & mineral shows (www.diwolf.com). My Road Report article, “Visiting with DiWolf,” appeared in the August 2020 R&G magazine.

Also, 2018 Lapidary Hall of Fame inductee Bernie Emery will be teaching the cabochon class. You can read my Road Report article about this great teacher, “Hall of Famer Bernie Emery,” in the May 2020 R&G magazine.

For a detailed story about the Wildacres Retreat and Workshop, you can read my article in the April 2019 issue of Rock & Gem magazine.

Author: Helen Serras-Herman

Helen Serras-Herman, a 2003 National Lapidary Hall of Fame inductee, is an acclaimed gem sculptor and gemologist with over 37 years of experience in unique gem sculpture and jewelry art. Visit her website at www.gemartcenter.com and her business Facebook page at Gem Art Center/Helen Serras-Herman.

 

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]]> https://www.rockngem.com/revived-interest-shines-on-the-natural-bridge-of-virginia/ Tue, 13 Apr 2021 11:00:22 +0000 https://www.rockngem.com/?p=14024 Editor’s Note: This is the second in a two-part series about the Natural Bridge of Virginia. Be sure to enjoy Part I >>> By Deborah Painter I visited the Natural Bridge of Virginia in August of 2019 with my friend David Hawk, who wanted to see it for some years but had never been able […]

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]]> Editor’s Note: This is the second in a two-part series about the Natural Bridge of Virginia. Be sure to enjoy Part I >>>

By Deborah Painter

I visited the Natural Bridge of Virginia in August of 2019 with my friend David Hawk, who wanted to see it for some years but had never been able to spare the time when he was in this part of Virginia. We wanted to collect some representative dolostone also. Near U.S. Route 11, approximately 0.47 miles north of the visitors center and at latitude 37° 38’ 05.65” North and longitude 79 ° 32’ 37.76 West, we were able to collect some loose specimens of dolomite on private land wherein permission was obtained from the owner. They displayed interesting features that looked like bits of Chepultepec limestone and a few small white markings.

Dolostone is a durable rock but, like all lime-based sedimentary rock, is vulnerable to chemical and physical weathering. The stage road of the 1800s that crossed the Bridge then became a paved road for automobiles and trucks as the stage road became absorbed into a portion of the main north-south roadway corridor through the Shenandoah Valley, U. S. Route 11. This road still uses the Bridge as an official crossing.

Yet, even with the utilization of regular U.S. government-mandated bridge inspections beginning in the late 1960s, no formal inspection of the stone span was carried out until very recently to determine if it was suitable for sustained use in the era of large diesel trucks. The construction of Interstate 81 from New York south to Tennessee was to some degree helpful; some of the heavy traffic that once used the Bridge would use the modern multilane highway.

MODERN PRESERVATION EFFORTS

One would think that this scenic wonder would always be afforded the preservation worthy of its historic significance. The private owners of the Natural Bridge at Cedar Creek did their best to preserve the saltpeter cave and native vegetation, including the extremely old arbor vitae trees along the trail from the Visitors Center to Lace Falls, but their ability to keep the gorge free of vandals and graffiti artists and to preserve the natural resources of the land to the north, south, and west was limited. They also had no control over highway use.

Angelo Puglisi was the most recent private owner, having purchased the complex, including the Natural Bridge Hotel, in 1988. When he made the announcement in 2013 that he planned to sell the property, there was the possibility that it might be divided up into smaller tracts with multiple ownership. A zipline concession approached him about purchasing rights to run a zipline from the top of the Bridge. This sort of over commercialization would harm its scenic, historic, and natural assets. Rockbridge County and the cities of Buena Vista and Lexington passed resolutions stating that the Bridge was an icon for the Commonwealth and better stewardship was needed. Land trusts throughout the United States worked together. The Rockbridge Area Conservation Council and the Valley Conservation Council formed the Friends of the Natural Bridge.

A nonprofit Virginia Conservation Legacy Fund was headed by Roanoke, Virginia, resident and healthcare executive Tom Clarke. Mr. Puglisi donated 187.8 acres, and the group paid for another 1,299.7 acres with a loan from the Virginia Clean Water Revolving Loan Fund from the Virginia Resources Authority and the Virginia Department of Environmental Quality. Thanks to Mr. Puglisi and the Virginia Conservation Legacy Fund, the Natural Bridge and Visitors Center, as well as hundreds of acres surrounding them, became part of the state parks system in 2016. The Natural Bridge Hotel and Conference Center remains in private ownership by Mr. Clarke’s nonprofit organization.

Because the Bridge was now part of the Virginia Department of Conservation and Recreation, the Department made an agreement with the Virginia Department of Transportation to test the Bridge at last. Geologists were subcontracted in early autumn of 2017 to perform varied methods of nondestructive testing, including electrical resistivity, geophones (small seismic sensors), and Ground Penetrating Radar testing.

The conclusion of the testing is that fractures and internal voids have developed in the dolostone. It is inconclusive whether this is the result of vehicular use, but to err on the side of caution, the Virginia Department of Transportation is studying alternative routing for this segment of U. S. Route 11, diverting it from the Bridge, and is writing an environmental document toward that end.

For a few decades prior to the sale of the tourist complex, public visitation had decreased. But the establishment of the Natural Bridge State Park boosted visitor use dramatically. The park rangers furnish a vehicle that will drive tired visitors back to the visitors center when they return to the Bridge at the end of their hike from Lace Falls. This might account for some of the increased visitor traffic, since there are four flights of timber stairs leading from the canyon back to the crest of the hill!

Our August 2019 trip to Natural Bridge State Park afforded me many pleasant surprises after not visiting this beautiful site for a few decades. The price for visiting, $14 per person over 13 years of age in the 1990s, is now $8. The vehicle ride is included, although during the COVID-19 health crisis it has been temporarily discontinued. Signage along the trail now prohibits visitors from entering the saltpeter cave to avoid disturbing roosting or hibernating bats. This prohibition is strictly enforced. Other sensitive habitat areas are marked “no trespassing.”

Another addition is a recreation of a Monacan Indian village along the trail, said village’s restoration being supervised by descendants of the Native Americans who had camped and lived in the gorge.

The State Park is located at 6477 South Lee Highway, Natural Bridge, Virginia. For more information, or to plan for a trip to the Natural Bridge of Virginia and area destinations, visit their web site at http://www.dcr.virginia.gov/state-parks/natural-bridge.

The Caverns at Natural Bridge, not a part of the State Park, are very near at 15 Appledore Lane, Natural Bridge, Virginia, 24578, and are a very interesting karst feature in their own right.

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]]> https://www.rockngem.com/7-questions-with-steve-voynick/ Tue, 13 Apr 2021 11:00:16 +0000 https://www.rockngem.com/?p=14036 Editor’s Note: As part of our year-long 50th Anniversary celebration, we will feature Q&As with regular Rock & Gem contributors and others in the community. This profile showcases Rock & Gem contributor and Rock Science columnist Steve Voynick, a member of the Rock & Gem team since the 1980s.   Rock & Gem: Discovery appears […]

The post 7 Questions With Steve Voynick first appeared on Rock & Gem Magazine.

]]> Editor’s Note: As part of our year-long 50th Anniversary celebration, we will feature Q&As with regular Rock & Gem contributors and others in the community. This profile showcases Rock & Gem contributor and Rock Science columnist Steve Voynick, a member of the Rock & Gem team since the 1980s.

 

Rock & Gem: Discovery appears to be at the center or part of various careers you’ve enjoyed during your lifetime (photographer, marine salvage diver, hard rock miner, and science writer). Please describe how these careers contribute to your study of minerals, rocks, and geology.
Steve Voynick: Photography taught me to look at things objectively; in salvage diving, I learned to expect new discoveries every day. Hardrock mining was a lesson in looking at minerals from different perspectives, while science writing provided a way to organize and clarify all that I had discovered and continue to discover.

RG: What inspired your appreciation for minerals, rocks, and gems, and how long have you held this fascination?
SV: I was raised in a heavily industrialized section of New Jersey where the only mineral-collecting “locality” was the main line of the Pennsylvania Railroad, which was only a block from my home. The rail-bed ballast was diabase basalt from the northern New Jersey traprock quarries. It was laced with vugs filled with small but beautiful crystals of quartz, calcite, prehnite, and a half-dozen different zeolites. I began collecting “ballast specimens” when I was 12 years old and have been fascinated with minerals ever since.

RG: Who are three of your most significant mentors in life, and why?
SV: I’d begin with my college professors who made science understandable and enjoyable, and the many mine geologists who generously took the time to explain ore emplacement, mineral identification, and the geology of ore deposits. I’d also include Bob Jones, whose R&G articles served as excellent “go-to” examples when I began writing about minerals.

RG: Of the places you’ve been in the world, where do you feel drawn to return? And what is one place you’ve never been but long to visit?
SV: I’d like to revisit the mines, ruins, museums, colonial architecture, and people of Potosi, Bolivia, a place with a timeless quality that just exudes history. And among the many places I have never been to but would like to see, the diamond mines of northern Canada would be high on the list.

RG: Do you have a type of rock, mineral, or gem that is among your favorites, and what makes it so?
SV: From my mining experiences, I picked up a special interest in ores and ore minerals. Even though most ores are not visually impressive, I’m intrigued by their histories, economic significance, and the milling and smelting technologies that underlie their conversion to useful mineral commodities.

RG: Spending as much time as you have with rocks and making discoveries, what are two of the most important tips you can share about making the most of hunting for and studying rocks?
SV: My interest in minerals goes beyond crystal structure, color, and specimen value. I’m fascinated by the many ways that minerals have impacted every aspect of society from history and economics to art, culture, and technology. Learning about these impacts has been an ongoing education that has added another dimension to mineral collecting, enriched the overall collecting experience, and made each and every specimen mean something special. I’d encourage every mineral collector to look beyond the visual appeal of minerals and learn the history and stories behind them.

RG: What is your hope for the future of the rockhounding, mineralogy, and lapidary hobby and industry?
SV: My hope for the future is that more young people will become interested in mineralogy, geology, and paleontology, both professionally to advance the sciences and as amateurs to enrich and sustain the hobbies. Working toward this goal, I see that some clubs have outstanding youth programs, and I especially admire the work of R&G’s Jim Brace-Thompson.

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]]> https://www.rockngem.com/a-historic-virginia-wonder-with-a-promising-future/ Mon, 12 Apr 2021 14:28:41 +0000 https://www.rockngem.com/?p=14012 Editor’s Note: This is part one of a two-part series about the Natural Bridge of Virginia. Be sure to enjoy Part II>>> By Deborah Painter During the era of the 1700s when North American colonies were under British rule, a certain intelligent and educated man by the name of Thomas Jefferson heard of a remarkable […]

The post A Historic Virginia Wonder With a Promising Future first appeared on Rock & Gem Magazine.

]]> Editor’s Note: This is part one of a two-part series about the Natural Bridge of Virginia. Be sure to enjoy Part II>>>

By Deborah Painter

During the era of the 1700s when North American colonies were under British rule, a certain intelligent and educated man by the name of Thomas Jefferson heard of a remarkable natural arch in west central Virginia, southwest of his Charlottesville home. He purchased acres of land surrounding the stone arch from King George III for twenty shillings. Since Jefferson bought this land in the year 1774, two short years before his penning of the Declaration of Independence, it was a well-timed sale. The future third President of the United States was immensely interested in both architecture and natural history and showed his understanding of both in his description: “….. the arch approaches the semi-elliptical form, but the larger axis of the ellipsis, which would be the cord of the arch, is many times longer than the transverse.”

Cedar Creek runs beneath the Natural Bridge of Virginia, which at one point was considered an original Natural Wonders of the modern world. The creek flows through a gorge. Native Americans of the Monacan tribe had for many thousands of years camped beneath Virginia’s Natural Bridge during hunting expeditions and made use of Cedar Creek’s water. They, as well as the game they hunted, also found the bridge itself useful as a crossing. The game trail later became part of a stage road that crossed the span. Rockbridge County derives its name from this famous feature.

Early visitors were awestruck by how this towering dolostone and limestone arch resembles a bridge built by human hands. It is approximately 215 feet in height from the top of its arch to the trail below and 90 feet from end to end. Americans of European descent were generally unfamiliar with natural stone arches in the 1700s and early 1800s and did not know of the thousands of natural shrink-swell created sandstone arches in what is now known as Arches National Park in Utah. In the Victorian era, the Natural Bridge was further promoted by an 1835 painting by Jacob Caleb Ward. Today, it is displayed at the Nelson Atkins Museum in Kansas City, Missouri. The Pennsylvania Railroad used this painting as its logo for many years.

EXAMINING THE GEOLOGY OF THE STORIED ARCH

Why are there so few limestone or dolomite spans of similar nature and appearance worldwide? The answer is to be found in the karst geology of the Natural Bridge area. The Appalachian Valley (known locally as the Shenandoah Valley) is unusually narrow in the area near Natural Bridge and the City of Lexington. The valley is Cambrian and Ordovician in age, sedimentary rocks that were folded and thrust faulted. Karst topography characterizes the Natural Bridge area. Near the Natural Bridge and Natural Bridge Station is Short Hill, a small hill that is a textbook example of a synclinal mountain.

The Natural Bridge itself is composed of two sedimentary rock formations: massively bedded, dense light gray arenaceous dolomite (dolostone) of the Beekmantown Formation of Ordovician age and dark blue limestones of the Chepultepec Formation, also of Ordovician age (Spencer, et al, 2007). These are all marine clastics.

Cedar Creek is believed to have begun as an above-ground stream less than one million years ago. It is entrenched at its mouth at the James River near Gilmore Mills for roughly 3.97 miles upstream of the River to Red Mills near the Bridge. In his 1968 paper on Rockbridge County geology, geologist Edgar W. Spencer of Washington and Lee University built his hypothesis of the formation of the span upon earlier hypotheses promoted by H. P. Woodward in 1936 and by F. J. Wright in 1934. Woodward and Wright stated that the stream known today as Cedar Creek was part of the karst system of underground rivers, capturing water from Poague Run two miles to the north, contributing to the larger drainage basin.

The creek’s larger flow helped to form the present-day gorge or small canyon, significantly increasing the distance from the bottom of the water flow to the roof of the underground channel. Extensive faulting characterizes the bedrock here. Over a period of perhaps 500,000 or more years, the cave ceiling above that underground river collapsed bit by bit due to faulting, erosion, and weathering, then ultimately disappeared.

REMNANT OF A CAVE FORMATION

Spencer’s, Woodward’s, and Wright’s hypothesis for the existence of the Natural Bridge is the accepted one today. As they stated, the Bridge is the sole remnant of that cave roof and still stands due to the strength afforded it as the midpoint of a syncline. Today, the “Lost River”, about one-half mile upstream from the Natural Bridge, is an example of an underground stream supporting the hypothesis of the underground river. Water from the side of the gorge flows into the Cedar Creek, much as the ancestral Cedar Creek underground river allegedly flowed into Cascade Creek that flows parallel to Cedar Creek. A small section of the rock between Cedar Creek and the bedrock of the gorge was blasted away along the visitors’ trail so that one can hear the underground river rushing along, mostly out of sight.

The various owners of the Bridge after Jefferson no longer owned it established a hotel, later to be named the Natural Bridge Hotel, to accommodate the many visitors who traveled to see this sight. The owners preserved many natural heritage resources along the streambank trail leading to Lace Falls. One such resource is a cave where bat guano was harvested hundreds of years ago to make saltpeter, a component of gunpowder. This was a source of income for Thomas Jefferson from his investment. Several extremely old specimens of arbor vitae (Thuja occidentalis), also known as eastern white cedar, gave the creek its name and still provide shade along the steps leading from the modern visitors center to the trail.

These individual trees are up to 700 years old. A dead trunk has been preserved in situ; the tree died in 1980 at the age of approximately 1,600 years. Decades ago, the owners built a concrete footpath from the top of the gorge down past the trees to the gorge, and a stone wall separates the visitors from the creek along portions of the 0.9-mile-long trail where the grade is steep. Interesting features near the span along the gorge are fossil moss being formed in the open as calcite-laden water flows almost constantly over the moss, the aforementioned saltpeter cave and lost river, younger specimens of arbor vitae, and riffle and pool complexes and small rapids and falls at various points along the trail, providing prime habitat for a variety of fish and invertebrates. At the end of the trail is a 29.5-foot-tall cascade known as Lace Falls.

For more information about the modern-day efforts to preserve this special locality, read Part II, “Revived Interest Shines on the Natural Bridge of Virginia.”

To learn more or to plan for a trip to this fascinating natural destination, visit https://www.dcr.virginia.gov/state-parks/natural-bridge.

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