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ACLT’s Executive Director Receives 2021 Maryland Sustainable Growth Award

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ACLT is very pleased to announce that Executive Director Greg Bowen has been awarded the 2021 Maryland Sustainable Growth Award in the Leadership Category from the Maryland Department of Planning! Watch this short video documenting Greg’s achievements in advocating for land preservation and sustainable growth throughout his lifetime.

According to a Md. Dept. of Planning press release: “The awards recognize individuals, organizations, and programs that exemplify well-planned economic and community development initiatives throughout the state.

“These awards recognize people and projects from across Maryland that bring creativity, innovation, and passion to our communities,” said Governor Larry Hogan. “Our administration is proud to honor and celebrate their commitment to helping change Maryland for the better.” 
The 10 winners are individuals and organizations that demonstrate their commitment to sustainable growth – development or redevelopment that is compact, walkable, and takes advantage of existing infrastructure while preserving the rural landscape – in Maryland. 
“Resourcefulness, innovation, and creativity are all part of what makes Maryland a leader in cultural preservation, community and economic development, and environmental stewardship,” said Maryland Department of Planning Secretary Robert McCord. “I congratulate all of the winners for their efforts that not only demonstrate how we should look at the built and the natural environment, they help to revitalize and improve the quality of life in their communities.”
The 2021 Maryland Sustainable Growth Awards in Leadership:
These awards are for activities or accomplishments that advance public appreciation, understanding or involvement in promoting smart growth and sustainable communities at the state, regional, or local level.
Greg Bowen – Greg Bowen’s dedication to his home and his community, the practice of planning, and to land preservation in southern Maryland and throughout the state, defines a 40-plus-year career that continues not far from where it started. He has been a steadfast advocate for land use, preservation, and sustainability, leading the way for many projects and ideas that have benefitted Maryland’s agriculture and forestry community.

In accepting the award, Greg thanks ACLT Charter Member Randi Vogt, currently an ACLT Board member, for coming up with the idea of using Transferrable Development Rights to direct growth away from valuable farm and forestland, and credits the leadership of the late Senator Bernie Fowler and Delegate Tom Rymer for shepherding Calvert County’s land preservation program through to adoption by the State. Randi’s idea blossomed into one of the nation’s first Agricultural Preservation Programs, permanently preserving thousands of acres of land since its inception in the early 1970’s.

“I am thrilled to have had the chance to see an idea form,

to help imagine how it would work,

and then to work with many others to turn it into success

over my lifetime.” – Greg Bowen

 

Greg is also grateful to the many farmers who participated in the Ag Preservation Program, County Commissioners who supported sustainable growth, and Planning and Zoning staff who implemented the programs. Finally, Greg thanks the ACLT Board of Directors for giving him his “dream job” and to staff and volunteers “who make miracles happen regularly”.

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Remembering Bernie Fowler

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By Greg Bowen, Executive Director, and Randi and Peter Vogt, Charter Members

Bernie Fowler was a gentle man, a gentleman, a visionary, and a natural leader. He had a long-standing, positive impact on Calvert County and on the American Chestnut Land Trust.

Bernie was first elected as a County Commissioner in 1970, just as major events were shaking up this sleepy, economically depressed county. A nuclear power plant was about to be constructed. Pennsylvania Avenue (MD 4) was being extended into the county and Washington, D.C. residents were seeking affordable lots in the rural countryside. County population was beginning to take off. Bernie began to  despair over seeing Calvert’s farm communities disappear. Meanwhile, already in 1969— even before estuarine scientists- he had noted a deterioration in water quality in his beloved Patuxent River. 

Bernie Fowler, Calvert County Commissioner (March 30, 1924-December 12, 2021)
Bernie Fowler at 2021 Wade In

At his direction, the Calvert County Board of Commissioners asked staff to research the current conditions of the county and to begin a comprehensive planning process with the extensive involvement of county citizens. The resultant 1974 Pleasant Peninsula Plan is still reflected in the best of Calvert County’s planning, including the creation of the state’s first county land preservation program. This led to the nation’s first Transferable Development Rights (TDR) program. The Plan also prohibited all new county waste-water treatment plants from discharging treated effluent directly into waterways.

The TDR Program, and the later addition of the Purchase and Retirement programs, have preserved or helped preserve two thirds of all the lands protected in Calvert, including nearly all of the lands that ACLT was able to purchase and preserve during the first two decades. After leaving elected office, Bernie became a member and strong supporter of ACLT. In 1994 he gave a keynote speech at the inauguration event for what we now call Double Oak Farm.

Back in the 1970’s, he instilled in Randi Vogt (founding ACLT member) and me — both of us long-term planners at the Department of Planning and Zoning – a passion for environmentally sound farm and forestland preservation.  After first working with Bernie as volunteers, we were both inspired  to pursue a planning profession.

Bernie “Never, Never, Never” gave up on his efforts to restore the Patuxent River and the Chesapeake Bay, a message he repeated this past June, his final Wade In. It is time for the rest of us to pick up the mantle.

View Randi Vogt’s Interview with Bernie Fowler on the Subject of Land Use Planning – October 2014 (Calvert Marine Museum Oral Histories Series).

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Sculpting the Parkers Creek Preserve

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What made our ravines, stream valleys, cliffs, ridges, and that mound rising above the salt marsh?

By Peter Vogt, Founding Member

Although part of the mostly gentle Atlantic and Gulf Coast Coastal Plain, the Parkers Creek Preserve (PCP) is scarcely a plain. That’s obvious even to first time ACLT hikers or Parkers Creek canoeists. Our preserved land rises locally to more than +160 ft above sea level, and some ravines are more than 100 ft deep. Adding canopy trees 75 to 140 feet high makes the land look even higher, especially when viewed from out in the Chesapeake Bay. The Calvert Cliffs form a formidable 50-100 ft high eastern rampart for the PCP. The preserve owes its dissected topography—at once as ideal for ecological diversity and nature hikes as it is challenging for farming or development—to the proximity to the Chesapeake of lands well above sea level. Steep gradients empower running water with the gravitational energy to  sculpt the land. While Minnesota may be the “Land of 10,000 lakes”, are we the “Land of 10,000 ravines”?

Not just an ecologically resilient ‘bio-preserve’ and nature park, the PCP is also a museum of geomorphology. That’s the study of landforms and the processes that shaped and are still shaping them: the topographic texture on which our living green carpet is draped. We have some interesting land forms, like that mysterious forested mound rising 43 ft above the Parkers Creek salt marsh. Hint—it was not built by ancient Native Americans or modern developers. Parkers Creek itself is a geomorphic oddity—flowing into the Bay when it was originally the middle part of a longer Battle Creek, flowing into the Patuxent.

Mankind is increasingly the main geomorphic agent (think bulldozers), but except for increased erosion caused by pre-modern farming, the PCP has been shaped by nature. However, nature tends to be a slow and patient sculptor of land—the morphing is too slow on our human time scales. In the PCP area, only the Calvert Cliffs and beaches change fast enough for us to notice.

Mapping and Displaying topography

Topography can be shown in different ways. A simple 3-D sketch or a photograph-ideally taken when the leaves are off the common deciduous trees and with some snow on the ground, can provide a local view. Contour maps became common years ago but may be greatly in error! An elevation contour is just a line on a map connecting points of the same elevation. ACLT trail maps have generally shown elevation contours—mostly at 20 or 30 ft contour intervals. Finer contour intervals would show more detail but too much clutter for a paper brochure. To see those details, go online and zoom down! Modern digital representations of topography—as computer illuminated and colored “hill-shade’ images–offer photographic realism, but elevations can’t be ‘read’ as on a contour map.  They are useful to hikers but not as useful as contours. Hill-shade images are generally computed from LiDAR (Light Detection And Ranging) scanners deployed on manned aircraft or drones. A laser is scanned (swept) back and forth across the ground at right angles to the flight path and at high rates. Laser pulse reflection times from the ground back to the sensor are measured and converted. Calvert County was first flown with LiDAR in 2005. In my opinion the greatest potential value of LiDAR for ACLT would be mapping forest canopy height—by subtracting laser reflections from tree tops from the ground elevations. A measure of forest type, age and health.

However valuable contour maps are, we humans relate much better to maps showing the ‘culture’ we have written—and keep rewriting– on the landscape. For the PCP that’s mostly roads and trails. We can also relate to ACLT’s ‘virtual culture’—property outlines with diverse colors showing the status of land preservation. We follow the progress of ACLT land preservation on maps which have practically no visible expression on the ground.

I liken this culture (e.g., roads, trails, power lines, buildings, property boundaries, cleared fields, etc.) as well as our natural vegetative cover to a palimpsest.  We humans ‘write’ our things on the land by erasing much of what nature has written. And then we may tear down historic buildings to make room for others. Other metaphors include black and white boards or painter’s canvases which, like the vellum or parchment (animal hide) of old– are just too valuable not to reuse. Of course the same is true for land—as our former MD Comptroller and Parkers Creek land owner liked to say about land “God made only so much of it.” Competing uses for the same land are a reason for land trusts like ACLT!

Nature slathers her corrugated canvas—the land– with thick ‘paint’—lush green in summer, more gray and brown in winter, sometimes even white. If you don’t like the ‘paint’ metaphor, how about a living carpet? While ACLT naturally concerns itself mostly with the ‘paint’ (or ‘carpet’), this article is about the underlying ’textured canvas’.  But metaphors have limits—paint is not alive and does not derive its sustenance from the ‘canvas’. In fact the soil and subsoil form a living underground world of roots, fungi, bacteria, and burrowing critters.

Figure 1 - Contour Map

While many ACLT members are familiar with PCP topography from hiking and canoeing, it’s challenging to orient oneself—can you locate your favorite ACLT trail?– on a contour map stripped of culture, particularly roads and trails.  Of course we recognize Parkers marsh and the Calvert Cliffs, but where for example is the ACLT South trailhead or Double Oak Farm?  To save readers the head scratching, I placed small yellow flowers at those three spots. The Yoe farmhouse sits near the headwaters of a major feeder ravine to Parkers Creek’s longest tributary. Double Oak is near the drainage divide (saddle) between the Horse Swamp creek watershed and a smaller tributary watershed further north. The ACLT South trailhead is appropriately very close to the drainage divide (interfluve) between the Parkers Creek and Governors Run watersheds whose preservation remains our land trust’s focus.

I also labeled that marsh mound (M), and drew some straight lines showing topographic trends of several ridges and valleys. (More about those later).

Land above +140’ is shown black and from +100 to +140 ft stippled. That helps readers orient themselves. A plain contour map-depending on how it is colored—a kind of natural Rohrschach test or paint- by- numbers painting.  Coloring selected elevation intervals with a felt tip or crayon can be therapeutic— much slower but more exciting than coloring by computer graphics. Nowadays geomorphologists routinely use computer graphics with different combinations of illumination and coloring to tease out subtle patterns of interest.

When PCP topography is shown this way, it looks dramatic. But modeled to scale in plaster at page size, the relief would only be around 1/16” inch, just enough to feel if you ran your fingers over it.

PCP Ecosystem Diversity and Resilience: Shaped by Topography and Geology

Our topography alone creates ecosystem diversity. North- facing slopes have a cooler, moister microclimate, different from the drier hotter south-facing slopes. Soggy flat valley bottoms support ecosystems distinct from those on flat ridge crests. The salt marsh, freshwater tidal and non-tidal swamps add further diversity, together making the PCP a microcosm of the Chesapeake Bay.

However, PCP topography also has a geologic connection—important for understanding our ecosystems. Where streams dissect a stack of flat-lying sediments or sedimentary rock, the layering is exposed—though maybe draped by soil–in valley walls. Progressively older layers crop out (or “subcrop”) further down the slopes. Of course the younger and higher a layer, the more of it has been lost to erosion. Grand Canyon is a grand example, but the PCP is fundamentally the same phenomenon, but for the smoother and 50 times lower relief. In neither case are the layers perfectly horizontal, but that’s a good approximation.

In contrast with the Grand Canyon- where old rocks are exposed in every side canyon- in the PCP we only rarely see any exposures of the Miocene layers even on the slopes of ravines. The reason is obvious—our Miocene layers were never turned into hard sedimentary rock, as have the ancient layers forming Grand Canyon’s cliffs. However, Miocene fossils are sometimes found in Calvert County ravine bottoms. Groundhogs may dig out of their burrows bits of fossil shells which however eventually dissolve in our acidic soils.

Our Miocene layers are tilted (dip) to the southeast at a few feet per mile. The shell marl exposed to Chesapeake Bay waves at the base of the Governors Run cliff would likely be encountered in a borehole at ca. 15-20 ft above sea level around 120 ft below Double Oak farm, which is about  3 ½ miles northwest of Governors Run. Shell marl is sediment which contains lime—in our case fossil mollusk shells.

The oldest PCP sediments above sea level were laid down 15 or 16 million years ago—around the middle of the Miocene epoch of geologic time- and are exposed near the base of the PCP’s Calvert cliffs. Some of these layers are so cohesive they crack into blocks just as harder rocks would. The youngest of these marine sediments date from around 10 million years and in the PCP are exposed around 100 ft above sea level. A total of three shell marls occur within this 100 ft section and where they intersect the ravine slopes buffer our otherwise acid soils.   This geologic buffering is the only way to explain the moderate pH of PCP streams—the pH is well above that of our rain. How well plants can utilize nutrients depends on soil pH! Tulip poplar, spicebush and pawpaw are common forest flora. Botanists have even spotted some PCP wildflower species otherwise known only from limestone substrates of the Appalachians.

 

 

Atlantic Retreat Is followed Potomac Advance

Around 8 million years ago the Atlantic Ocean retreated from what is now Southern Maryland. Relative sea levels likely fell, in part due to ice sheet expansion in Antarctica. From then until around 2 or 3 million years ago the Potomac and its tributaries flowed across here on their way southeast to the coast. The ‘fluvial’ (river deposited) sediments have more sand or even gravel, and very few fossils. In the PCP these “Upland Deposits” are present where our land is higher than about +100 ft (stippled or black).

Lacking shell marls and also low in nutrients, the Upland Deposits support flora which do well in more acidic soils—ACLT naturalists  can attest that pine, mountain laurel and even oak species are generally restricted to our higher elevations. Sands winnowed from the Upland Deposits by streams work their way downstream and eventually replenish beaches.

The presence of Upland Deposits capping Calvert County shows that the Patuxent must have formed after the Potomac switched its Coastal Plain course at the Fall Line, where it today turns sharply to southwest. Before that switch, the river continued on its SE course it still has across the Piedmont. What caused this course switch (similar in sense to that of the Delaware and Susquehanna) is beyond the scope of this article, but it ultimately initiated formation of the Patuxent River and thus the stream layout on the present PCP.

The Upland Deposits were laid down on a gently sloping plain—like that along the US Gulf Coast today. Remnants of this ancient plain are scattered around in Calvert, including the PCP. The wide field at the intersection of Parkers Creek Road and MD 765 is a great example, and the gently rolling terrain around Double Oak and Holly Hill. Nearly level lands erode also, but only very slowly:  Maybe just an inch per 1000 years! The original plain sloped very gently towards the east, but also covered what is now the Chesapeake Bay.

How PCP topography was born: Dissecting the Upland Plain by Headward Erosion

With the new Patuxent nearby, tributaries began to develop by headward erosion towards the west and east. Headward erosion means the tip or ‘head’ of a stream, ravine or gulley propagates upstream, i.e., ‘eats’ its way into the nearly level land. When past Calvert farmers plowed their fields right up to ravine edges, they soon noticed gullies growing into the fields and consuming their land.

As a valley or ravine lengthens, erosion of its margins cause them to widen. If there are any subtle remnants of the original SE flowing streams, I am not aware of them. Thus, the stream pattern we see today on the PCP began with streams flowing into the Patuxent starting very roughly a million years ago—accurate dating is challenging.  The streams heading west towards the Patuxent flowed from an upland drainage divide out in (and above) what is the modern Chesapeake. This was the divide between the Patuxent and Susquehanna watersheds. Parkers Creek was the middle part of a longer Parker-Battle Creek. The upland once between the present mouth of Parkers Creek and that divide was lost to cliff erosion. The divide elevation is unknown but had to be above the +45 ft elevation of the remaining short segment –the ‘dry valley’ utilized by German Chapel Road–of the old Parker-Battle stream.

Stream Piracy–How the Chesapeake stole Parkers Creek from the Patuxent

The present PCP topography, dominated by the east-flowing Parkers Creek is of geologically more recent origin but was also caused by headward erosion. This ‘stream piracy’ or ‘inversion’ makes our land unusually interesting but is challenging to explain in words. Cartoons would be better, but a computer animation movie would be best. Any computer-savvy folks want to help me explain how Parkers Creek was stolen from the Patuxent? Such a movie would also cover the SE to SW course switch of the Potomac.

Anyway, here in words:  We have had a succession of Chesapeake Bays, and each one caused more upland loss by cliff erosion. The penultimate Bay, ca. 125,000 years ago, had sea levels around 20 ft above today’s. When cliff erosion- perhaps from an even earlier Chesapeake Bay- first passed the old Patuxent-Susquehanna drainage divide, it was easy for an infant east-flowing stream to ‘eat its way’ upstream (headward erosion) along the channel of Parker-Battle Creek. Steeper gradients empowered young Parker’s Creek. The existing channel fill was soft and a valley already existed. How long it took for the new Patuxent-Chesapeake divide, i.e., the headwaters of Parkers Creek, to migrate to where it is today, crossed by German Chapel Road, is unknown.  I estimate that the piracy began as late as 150,000 years ago— we humans already existed but had not left Africa.

Although inherited from a tributary to the Patuxent, the Parkers Creek watershed is more deeply dissected today than a million years ago. The upland plains have shrunk to scattered patches and the ravines have become deeper. Much of these changes have happened in the last 600 thousand years—with their large alternations of high and very low sea level.

Thus, all of the present Parkers Creek watershed once drained west into the Patuxent. The Parkers tributary streams of course did not change direction, and the overall pattern of streams and ravines has not changed. However tributary stream and ravine gradients have been increased—and are still increasing as the cliffs continue to migrate west, locally slowed by human shoreline protection.

The steep gradients give stream water more energy to cut into the substrate and cut inland by headward erosion. As the cliffs retreat westwards, the Chesapeake Bay steals land from the Parkers Creek watershed: The present strip of land about 500 to 2000 ft wide (the Warrior’s Rest cliffs and much of Scientists Cliffs) now drains directly into the Bay. For example, the north fork of Governors Run (colored yellow) flows south parallel and just 350 ft inland from the cliffs. Absent human tampering, shoreline westward retreat by the Bay would capture this fork in just around 2000 years. Whether rejuvenated ravines pirated from the Parkers watershed, or brand new, these short ravines make up for their tiny watersheds with high energy, locally even forming small waterfalls during cloudbursts. Arresting shoreline retreat won’t stop the Bay from stealing more land from the Parkers Creek and Governors Run watersheds.

Farming activities by English colonists and their American descendants accelerated erosion of the Upland Deposits, particularly by the headward erosion of ravines. Many of these formerly active gullies are now stably forested.

The Parkers Creek Marsh Mystery Mound

The most unusual topographic feature in the Parkers Creek Preserve is an elongated mound or island rising about 43 ft above from the surrounding salt marsh. Trees covering the mound may increase its total height to more than 100 ft.  ACLT canoeists notice this on their first trip up the creek and might wonder if it was made by humans, for example by ancient Native Americans. However, there were no mound-building cultures here, and no evidence for an artificial origin. However, who’s to say the mound was never used as a lookout by scouts or hunters? The mound might have been made by past Parkers Creek meanders and meander cutoffs—forming intermittent oxbow ponds.  Alternatively, it may have formed by shoreline wave erosion during times when there was no marsh and no barrier beach. While the marsh mound looks to be a remnant of a formerly longer marsh island spur ridge, it’s strangely oriented in another direction: NW-SE. This shape might reflect past meanders but alternatively was caused in the absence of marsh and barrier beach by shoreline erosion from Bay or lagoon waves eroding its shores from the northeast.

 

The PCP Is About Water

 Water seems nearly the sole common denominator for what shaped and continues to shape the Parkers Creek Preserve (I said ‘nearly’—read on). Waters of the Chesapeake Bay gnaw at the cliffs slowly replacing our dissected uplands with a very gentle estuarine floor. Of course this only happens during interglacial warm periods with high sea levels, most recently the last 6000-7000 years. At other times the cliffs stay put as wooded escarpments.

Pore water trapped in Miocene cliff sediments helps erode them by freeze and thaw in winter.  Rain water washes sediment into the ravines and then into the Bay. Protracted rains soak into the ground, causing landslides on steep slopes. Cohesive Miocene sediments are fractured, letting water seep along joints, helping loosen blocks but locally carrying dissolved iron down as cement to strengthen the sediments (cliffs north of Parkers Creek beach). All the sediments eroded from the PCP and carried to the Bay had already been carried there by water—the Miocene sediments in the Calvert Cliffs and present everywhere below about +100 ft were deposited from Atlantic Ocean waters. Sediments comprising the ‘Upland Deposits’ were brought here by the ancestral Potomac.

 A Touch of Tectonics– Any PCP topography with structural control?

Is anything about our PCP topography NOT caused by the actions of water?  Maybe so, but subtle. Stream patterns developing and growing on uniform sediments produce the familiar dendritic patterns like the veins in a leaf. The two large PCP tributary watersheds south of Parkers look pretty dendritic.  

When geomorphologists look at accurate topographic maps, they keep an eye out for “structural control”. By that they mean faults or folds or even simple fractures (joints) that may have influenced the pattern of streams. For example, a fault in older deeper rocks might have become reactivated and propagated up into the overlying sediments and fractured them. The headward erosion of a stream would follow such a zone of weaker, more easily erodible sediment. Or, if groundwater had seeped down along a fault zone or joint system and deposited iron oxide, these sediments would be more resistant, avoided by a growing stream. In a landscape dominated as the PCP is with dendritic drainage patterns, a search for ‘structural control’ involves looking for longer straight valleys or ridges and regularities in trends and spacing. However not all faults are linear—a rising salt dome or a subsiding crater could have patterns of circular faults. If there is too much dendritic stream topography, structural control might not be recognizable, or people would argue about its existence. It’s a matter of ‘signal to noise’. We humans are great at pattern recognition, but we are also prone to see things not really there.

Let’s now first take some steps back and look at the geology of our region. Coastal Plain geology, even our dissected PCP, seems pretty boring compared to the western US. That’s because we sit on a passive continental margin, which, since plate tectonics separated North America from Africa around 175 million years ago has been very peaceful. Our margin is slowly subsiding and accumulating erosional detritus—sediments—eroded and weathered from the Piedmont and Appalachians. Under the PCP lies about a half mile of shallow marine or marsh sediments—the oldest below us were laid down around 125-150 million years ago. That’s the long term subsidence—averaging about one foot per 50,000 years. A rate trivial compared to our present sinking rate—one foot per 300 years—the delayed response to the “recent” great Laurentide ice sheet and its melting. The part of our relative sea level rise we can’t change but which will continue at slowly decreasing rates (discussed in Quo Vadis article).

However passive the continental margin, our plate interior has been under horizontal compressive stress beginning soon after we separated from Africa. Due to the slow stress buildup, our strong crust, and the stress being compressive, it takes many centuries or even millennia before there is enough stress to break the rock and thereby produce an intraplate earthquake, but when one happens, it is felt over a much wider area (less attenuation of seismic waves in old crust) than a comparable one on the West Coast.

The 2011 Louisa, VA quake (magnitude 5.8) was clearly felt here in Calvert, as was the 7.0 shock that destroyed Charleston, SC in 1886. If cliffs are shook in a strong earthquake, landslides can happen, so seismicity can be a geomorphic agent. As far as I know, the Louisa shock did not cause landslides along our Calvert Cliffs—it was close but not close enough. The Charleston quake was much too far away but I doubt anyone checked the Calvert Cliffs for new landslides.

The Louisa shock occurred in the Piedmont and the Charleston one on the Coastal Plain, but they both involve reverse motion on steeply dipping reactivated faults. Reverse fault motion involves one side shoved up over the other. Closer to Calvert, the Stafford faults in Virginia and the Brandywine fault system under Charles County, as well as the fault under Louisa, are also reverse faults. They most all trend (strike) NE to NNE. In all these cases, ancient preexisting faults were reactivated. The faults remained as zones of weakness—where repeated breakage is most likely. (Anyone who breaks apart wooden furniture notices that breaks often follow old glue lines or other joinery). The faults under Louisa and Charleston had been normal faults (extension) as preludes to formation of the Atlantic by plate tectonics. Long before that, the same faults had been involved in the continental collisions of the Appalachian orogenies (mountain building episodes) that closed an earlier ocean from 500 to 250 million years ago.

There can be little doubt that the ancient crystalline and metamorphic rocks a half mile and more below Calvert County are criss-crossed by earthquake faults and other structures. While modern technology is more than adequate, who would pay for a number of boreholes to learn more? Whether, where or how often any of these faults could rupture again is unknown, but if faulting happens, it must be very rare. However, the buried Taylorsville Basin across northern Calvert County, formed around 225 million years ago, is bounded on one side by a NNE trending fault similar in age and trend to those mentioned above which have ruptured in more recent times. The Miocene sediments exposed in the Calvert Cliffs (laid down from 18 to 8 million years ago) are not offset by faults except at one site along the southern cliffs. A high angle reverse fault has offset the Miocene layers so must have been active until at least 8 million years ago. It is unknown whether younger Upland Deposits were also offset. The trend of this “Moran’s Landing Fault’ remains unknown, but given its location between the LNG terminal and the nuclear power plant should be investigated.

Even in the absence of faults (with displacements) crustal stress can create patterns of simple cracks, called joints. Topography can offer clues—any evidence for ‘structural control’ in PCP topography? I think so, but the evidence is subtle. Some of our lower Parkers Creek watershed topography, although much carved out by water, seems too linear to have been created entirely by water- I drew ridge lines in red and valleys in blue. Possible structural control guiding the original courses of streams. There appear to be two main trends, at right angles to each other: A NNE trend and an ESE trend. These lineations are somewhat regularly spaced—about 1500-2000 ft apart. One of the NNE ineations is that half-mile long ridge just east of Double Oak.

One NNE ridge trend happens to align with the Parkers mound and associated spur, both relics of former higher and wider features.  Maybe the location of this mound was not solely the work of stream erosion and meanders. When the most conspicuous (and most easterly) ridge trend is extrapolated, it grazes the cliffs north of Parkers Creek. The sediments in the lower parts of those nearly vertical cliffs are very cohesive, with joints locally cemented by iron oxide.  A clue that dissolved iron percolating down along joints and precipitating in the Miocene sediments may have been a reason for this ridge. Maybe.

Tectonic origin of regular cracks (fractures or joints) in the cliffs?

 

Any independent evidence for NNE and/or ESE trending structural trends? Maybe. The lower, most cohesive layers in the Calvert Cliffs exposed in the PCP just south of Parkers Creek beach have been fractured by some process. Modern cliff erosion is in the form of blocks caving off along those fractures.  There are numerous such joints spaced regularly around one foot apart, steeply dipping. The trends (strikes) are hard to measure accurately but appear to be E-ESE. These joints may have formed by thermal contraction and extension during the annual air temperature cycle, but if so would not continue deep into the cliff. If the joints are tectonic, they would extend through the ground under the cliffs. Some of the block failures may be controlled by NNE trending joints, but any cliff naturally fails along cliff-parallel joints. Whether or not these two sets of joints and resultant block collapses are partly of tectonic origin, they represent geomorphology processes working fast enough for humans to study.

It’s likely but not proven that sediment layers under the PCP have been fractured (by long term horizontal intraplate stress) along the well known regional NE to NNE structural trends. When our tributaries to Parker-Battle creek first formed, they would likely have propagated in one direction by headward erosion along zones of sediment weakness such as fractures (joints) or even, at depth, minor faults.

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The Secret Lives of Insects #10

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"Arachtober" 10th is International Jumping Spider Day!

By Judy Ferris, Master Naturalist & Guest Blogger

Do you Need a Warm, Fuzzy Hug?

Even folks who fear spiders must admit that this fuzzy-little jumping spider is cute as can be. She comes complete with ‘horns’, 8 eyes, and wears a tres chic fluffy sweater! Add to this her inquisitive engaging personality and she is the perfect ambassador for International Jumping Spider Day!

Though she looks ferocious, this little Canopy Jumping Spider is only 1/2 inch long. Look closely at her face and you will see the vivid green chelicirae (teeth) peeking out from the fur. Glowing, green teeth! Who could resist? Now stare deeply into the spider’s eyes. On a large screen, your eyes begin to play tricks on you as you attempt to stare into all four eyes at once! Like most Jumping Spiders, the Canopy Jumper has 8 eyes arrayed around its head, 4 in front, 2 on the sides of the head, and 2 in the back. Jumpers have some of the best vision of any animal on the planet. Some species can even see in ultra-violet colors! Vision is key, since Jumping Spiders do not create webs to catch insects. Instead, they leap through the air to capture their prey.

Canopy Jumping Spider - Phidippus otiosus. Overall white/gray/brown color with boldly striped legs.
Meet the Bold Jumper - Phidippus audax . Note the insect - probably a fly - sticking out near the spider's mouth. Jumping Spiders are efficient insect hunters.

Watch the video below to meet a cousin of the Bold Jumper – the Portia Spider of SE Asia and Australia.  Portia Spiders have excellent vision and are intelligent hunters. 

Most Jumping Spiders can jump about 20 times their body length. That may sound scary, but if you do the math, it comes out to a leap of about 12 inches.  The over-achiever Bold Jumper, however, can leap 50 times its body length; a little over 2 feet.
Bold Jumper - Signature color is black with variable white, reddish, or golden accents.

“Portia the Jumping Spider” — 5 minutes.  Beautifully filmed by the BBC. Video not playing? Click here:  https://www.youtube.com/watch?v=UDtlvZGmHYk

You may have noticed that many of Portia’s Jumping Spider cousins here in the United States seem to have an affinity for travel, or more likely, warm snuggly automobiles. They have a flair for appearing unexpectedly in your car as you zoom down the road! The devilish little arachnids revel in zipping across your dashboard, or even your windshield, at critical vehicular moments. Meanwhile, you attempt to focus on driving rather than speculating about the various places a spider could land should it choose to leap. Naturally, once the car is parked the spider vanishes into an inaccessible, dark hidey hole. Hopefully, it has disappeared beneath the dashboard, rather than somewhere in your clothing!

Bronze Jumper - Eris militaris. Brownish in color with a distinctive golden mask.
As they move about in their world, Jumping Spiders habitually leave a continuous trail of silk. Like leaving a trail of bread crumbs, this delicate line helps them with navigation. It also serves as a safety line and a drag line to control their landing when they leap. Perhaps most important of all, the trailing strand is also laced with pheromones which assist in finding a mate.
Extensive study of Jumping Spider courtship reveals that male Jumping Spiders not only dance, but also ‘sing’ to entice females. Phase 1 in the courtship process is for the male to send a nice, soothing vibe to the female.  ‘Singing’ is accomplished by rubbing together the spider’s 2 body segments. This creates a vibration that travels through the ground to the female. In some species, the males thump their abdomens on the ground or tap their feet as well. Experiments have shown that when males are prevented from sending vibrations, the dissatisfied females are four times as likely to cannibalize the males. Ouch! (Heimbuch 2017) If singing and tapping doesn’t work, it’s time to escalate to Phase 2 – the  Disco Dating Option. Think “Saturday Night Fever” for stylin’ male spiders. Lots of leg waving, posing, color flashing, hair twitching, and fancy dance steps. All aimed at mesmerizing the female. The male’s very life depends on a good performance. If all goes well, the male is able to carefully approach the female, transfer his sperm to her, and escape without becoming a snack.
 
Australia is home to some of the planet’s most exotic spiders, including the beautiful Peacock Jumping Spider. Click on the link below to view the elegant and potentially dangerous courtship ritual of a male Peacock Spider as it attempts to woo a judgmental mate.
“Peacock Spiders, dance for your life!” Excellent video from BBC – 5 minutes. Video not playing? Click here: https://www.youtube.com/watch?v=5qkzwG2lLPc
Now that you have been thoroughly introduced to Jumping Spiders, what will you do if you find one of these creatures in your home? Should you kill it? Heck no! Spunky though they may be, these tiny spiders are far more likely to run away than to attack you. Their bite is not poisonous, although it may itch. Think of a Jumping Spider as a household helper; happiest when it’s running around, eliminating unwanted insects from your home or garden. Though they may not be totally receptive to a warm, fuzzy hug, you can do Jumping Spiders a favor by simply ignoring them as they go about the endless business of pest control.
 
Finally, take a moment to sit back and flip through Jumping Spider photos taken by a spider enthusiast in Singapore for International Jumping Spider Day 2018.  To gaze deeply into puppy dog-like spider eyes and view a variety of fur-trimmed spider costumes, check out the link below.
 
Click on the link, then scroll down for a celebratory collection of
Jumping Spider Glamor Shots.

 

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The Secret Lives of Insects #8

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Dragonflies: Jewels of the Insect World

By Judy Ferris, Master Naturalist & Guest Blogger

Needham's Skimmer male. Photo taken in ACLT gardens.
While brightly colored insects are noticed and admired, Dragonflies are the true jewels of the insect world. Their wings shimmer in a glittering array of patterns. Their huge eyes glow like gems and their bodies are colorfully painted. Add to this their extraordinary flight capabilities and clearly, this is no ordinary creature!
A mosquito's-eye view; face to face with a dragonfly. Photo by Yogendra Joshi CC by 2.0
To scrutinize a Dragonfly is to peer into the past. Starting with the head, we note that unlike nearly all insects today, dragonflies have minimal antennae. Their vision, however, is acute. Massive compound eyes encompass nearly their entire head. Each eye has about 30,000 facets; receptors which bring visual information to the dragonfly’s brain. (Olberg 2009) Additional adaptations ensure that their color vision is probably better than ours! (Ryo Futahashi et. al 2014) How generous of Mother Nature to endow a 320 million-year old species with vision that modern insects, and even humans, would envy. Ever had trouble sneaking up on a dragonfly? Now you know why! 60,000 eye facets are monitoring your every move!
But nature’s gifts don’t stop at the dragonfly’s head. Its legs are one of the secrets of its success. A dragonfly’s thorax is specially modified to accommodate all of its legs up front. Pushing the legs forward in this way essentially makes the dragonfly into a flying basket for scooping up food. Spiny legs ensure that no insect escapes capture. The dragonfly then, snags prey on the wing, uses its mouth to rip off the wings so that the captive can’t escape, and feasts on its victim without ever having to land. What does a dragonfly eat? Glad you asked! Dragonflies are exclusively carnivores. Mosquitoes and midges are dietary staples, but anything that can be captured in the air, including Deer Flies, Butterflies, and other dragonflies, is fair game.  
Halloween Pennant dragonfly. Note the legs pushed forward on the thorax.

Watch this 1-minute video of a dragonfly eating a  mosquito. Note the positioning of the dragonfly‘s legs; basket-like and perfect for capturing prey.

Folks who study insects consider dragonflies to be ‘primitive winged’ because unlike modern insects, dragonflies are unable to fold their wings when not in use. Their wings are forever held out at a 90-degree angle to the body. Ah, but this is not just any old set of wings! The front and rear wings of a dragonfly are able to act independently from one another. This unique wing configuration is the reason that dragonflies are Masters Of The Air. They can hover like helicopters, turn on a dime, and dart swiftly from a standing start. Today’s modern insects flap their wings at a speed of about 1000 flaps per minute. Dragonflies? Hardly raise a sweat; flapping only 30 flaps per minute. These amazing flight capabilities are yet another source of envy for today’s insects! Perhaps primitive’ is not so bad after all!

Click below to watch a beautiful slow-motion video by BBC of a dragonfly in flight. 1 ½ minutes in length.

Dragonflies are superb hunters. But mighty though they may be, after hundreds of millions of years, they still remain tied to the water. Dragonfly nymphs (larvae) develop in water for months and sometimes years before becoming adults. You might expect dragonfly babies to be elegant and artistic. But NO! Dragonfly nymphs are the stuff of horror movies! Imagine a small (1/4 to 1 ½ inches long), crayfish-like creature with a large head containing a lethal lower lip (labium). The nymph’s lower lip is hinged, rather like bending your arm and tucking it in to your chest. The lip can shoot out, snag prey, and drag it back into the mouth so fast that if you blink, you’ll miss it!
 
To check this out for yourself,  watch this excellent 3-minute video from PBS ‘Curiosity Stream’ on dragonfly adults and nymphs.
Dragonfly nymphs eat the larvae of mosquitoes and mayflies, as well as tadpoles, and even small minnows. The nymphs themselves, of course, are a favorite food of frogs, fish, and snakes. It is estimated that the mortality rate of dragonfly nymphs may be as high as 99%! (Arnett 2000). Thus, no matter how lethal your lip is, if you are a nymph, it pays to have a good escape strategy.  Mother Nature had to work hard on this one but as always, came up with a novel solution.
    1. A dragonfly nymph has gills in its rectum. Thus, the nymph continually takes water in and out through its anus to breathe. [No. I am not making this up!]
    2. If threatened, the nymph uses the powerful muscles of its rectum to blast water out of the anus.
    3. Whoosh! Powered by the blast, the nymph is jet-propelled at high speed away from danger, leaving only a camouflaging plume of disturbed debris in its wake!
Each Dragonfly that reaches adulthood is a small miracle. Common Pondhawk female.
Dragonflies were perfect when they were created 320 million years ago and remain so to this day. In both the larval and adult stage they are master predators; helping keep mosquitoes, flies, and other pests in check. They also serve as an important food source for other creatures. Dragonflies are good indicators of a healthy environment and clean water. How wondrous that these jewel-like super-predators, capable of astonishing aerobatic and aquatic feats, still share our world and bedazzle us today.
 
It ‘s easy to be smitten by these astonishing insects! If you would like to learn how to attract dragonflies to your yard, check out the link below.
 
Tree hugger;  “How to Create a Dragonfly Garden”

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