The Virginia Geological Field Conference

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Feature photo: An outcrop showing boudinaged felsic leucosomes and quartzofeldspathic domains. The location is along the south bank of the South Anna River a few yards east of Route 673, Rockville, VA.

Article and photos by FMN Stephen Tzikas

Every autumn the Virginia Geological Field Conference (VGFC) provides geologists, university students, and the public an opportunity to participate in a geologic field excursion within the State. In 2022 the event was held November 11-12 and explored the Goochland Terrane, just west of Richmond, VA. Attendance levels usually necessitate the need for two coach buses to transport the participants to the various locations on the agenda. The event is usually hosted by universities, community colleges, and/or State organizations. The field experience is invaluable. The VGFC website provides the details and should be monitored: https://vgfc.blogs.wm.edu/

These conferences and field trips are not just found in Virginia, but they are not available in every state. Fortunately for Virginia Master Naturalists, our neighboring States have very active programs as well:

I highly recommend these State excursions as learning experiences for Fairfax Master

This is one of the many outcrops at Hidden Rock Park in Goochland, VA. These leucogranite dikes display boudinage structure.

Naturalists, even though only the VGFC excursion is applicable as FMN CE training.*  I have been to several of these and they are excellent, especially the ones found in northern states offering glacial geology exploration opportunities.

There were plenty of boudins at visited locations in the 2022 VGFC site itinerary. A boudin is a geological term for structures formed by extension (stretching), forming sausage-shaped boudins.

Photo: Close-up of the center of the outcrop in the photo to the right, above.

*Fairfax Master Naturalists: Enter CE using All continuing Ed ->Other and then make a note of the trip in the description field.

Save a Sapling: Pull Invasives

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Photo:  Plant NOVA Trees

Article by Laura Handley

One of the most satisfying moments of invasive plant management comes when you pull the last vine off a struggling native sapling, freeing it to claim its full share of sunlight and grow without restraint.

Volunteers with Fairfax County’s Invasive Management Area (IMA) program get to do just that twice a month at Idylwood Park in Dunn Loring. In a series of workdays, primarily on Saturday mornings, these volunteers have worked to clear invasives from a meadow along the park’s driveway. A wide range of people have participated so far, from scout troops to high-school students seeking service hours to venerable Virginia Master Naturalists. Several have brought family or friends to chat with as they work, taking advantage of the chance to socialize outdoors.

According to Patricia Greenberg and Gloria Medina, the coordinators of the IMA program, several of the saplings the volunteers have uncovered (including black walnuts, multiple species of oaks, and a large Honey Locust) were planted by the park service in the late 2000s. But the area around the saplings was left unmowed and unmonitored, allowing invasive vines to creep in from adjacent areas. By the time the volunteers started working, those invasives dominated the meadow.

The volunteers’ first challenge was to clear a path to the trees, which were blocked not just by the invasives but also by Poison Ivy and thorn-covered blackberry canes (both of which are native plants but which were blocking the way). Next came the delicate operation of untangling the vines from the young trees’ branches. Any vines growing out of reach were left to hang on the trees, where they will eventually die and fall down on their own. The final challenge has been maintenance: keeping the vines from re-growing to cover the trees again. After repeatedly cutting them to the ground failed to do the trick, Greenberg and Medina joined site leader Laura Handley one morning this fall to apply herbicide to the vines’ stumps. This targeted application should hopefully finish off the vines (while leaving the surrounding vegetation unharmed).

The rescued trees are often oddly shaped, their crowns pulled sideways and their trunks wrapped with spiraling vine-scars. But as they grow, now free of obstructions, they should straighten up and fill out. And by rescuing existing trees rather than clear-cutting the area, the volunteers have given the meadow a ten-year head start on the process of returning to a mature forest.

Once the meadow is clear of invasives, the group plans to spread seeds for native wildflowers over the ground they’ve bared — that is, if any of the ground stays bare. In the two years they’ve been working on the site, several native species have reappeared or expanded their footprint, including Common Milkweed, Canada Goldenrod, Wingstem, Foxglove Beardtongue, and New England Aster. This robust layer of herbaceous plants will help keep invasives from returning to the site and will serve as food and habitat for many native insects, birds, and other critters–and as the saplings grow, they’ll start to do the same.

Winter is a great time to rescue trees, since it is easier to get at them and cold temperatures are good for working. The winter workdays for this site will soon be posted to the IMA program calendar, and similar volunteer events in locations throughout Northern Virginia can be found on the Plant NOVA Trees website. https://www.plantnovatrees.org/rescuing-trees

Observations in Nest Engineering

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Article and photos by FMN Stephen Tzikas

Feature photo:  Eastern Bluebird nest, Box 3. May 1, 2021, Langley Fork Park.

Animals can have fairly skilled abilities, like that of a beaver building a dam, wasps constructing a hive, an octopus maintaining a garden to hide and reinforce its den entrance, or a bird building a nest. Birds can build nests in a variety of areas, urban or rural.

In 2021, I volunteered to become a bluebird monitor at the Langley Fork Park, in McLean, VA. It is one of the great variety of master naturalist programs available to volunteers. I was partial to it primarily because I had a pet parakeet as a child and knew how extremely intelligent and friendly these birds are. In 2022, I became the trail leader.

The Virginia Bluebird Society’s monitoring program offers a great opportunity to see new born birds very close. It’s not just the birds I find interesting, but also their nests. My favorite Bluebird monitoring document is found at this link from the North American Bluebird Society:

http://www.nabluebirdsociety.org/PDF/NABSFactsheetMonitoring.pdf

It is a useful document that discusses the identification of birds, eggs, and nests.

House Wren nest, Box 9, July 16, 2021, Langley Fork Park.

It’s all fascinating and perhaps the most interesting to me, as an engineer, is how nests are made. Each species has a unique nest. One might ask why and how? I haven’t found too much literature on why each type of bird builds a nest the way they do. So I will speculate a bit.   At Langley Fork Park the Tree Swallows and Eastern Bluebirds are the most successful birds inhabiting the boxes, with the Tree Swallows having a slight edge. In 2021, we had one successful House Wren nesting event. While maintaining the bird boxes this Fall, I noticed a mouse built a nest in a birdbox surrounded by overground shrubs, which allowed it to reach the entrance.

Eastern Bluebirds build neat, cup shaped, woven nests of fine grass or pine needles. Tree Swallows

Tree Swallow nest, Box 5, May 21, 2022, Langley Fork Park.

build nests of coarser grass lined with feathers. Their cup is flatter than those of Eastern Bluebirds. House Wrens build haphazard nests of twigs, occasionally lined with feathers. House Wrens pile twigs creating a cavity in which they choose to nest, acting as a barrier between nest and entrance. House Wrens can be fierce competitors for nest sites, but generally speaking, the House Wren, as a species not as competitive as the Eastern Bluebird or Tree Swallow, has a security structure embedded as part of its nest.

Birds can also build unlined eggless “dummy nests” in nearby boxes to reduce competition. Dummy nests are also built by males, perhaps to offer the females some choices on her preferred location and once chosen, can be finalized.

From the Factsheet link I provided, the mouse has a messy nest. Mice usually make their nest from a variety of materials, such as grass, leaves, hair, feathers, shredded bark, moss, cotton, or shredded cloth. My son had a gerbil as a pet. I can say gerbils are not as intelligent as birds. Given this observation of their fellow rodent, and that mice are quite timid and scared, their nests are conducive to hiding. A mouse did not make a quiver when I opened a bluebird box weeks after the end of a season and found a mouse nest. Its nest was built to hide at all costs. Upon emptying the nest the mouse quickly ran away.

House Wren nest, Box 9, side view from 2021 season.

Eastern Bluebirds and Tree Swallows, who are competitive and successful, perhaps have the luxury to build a more comfortable nest given their abilities to defend their turf. The Eastern Bluebird, perhaps being particularly skilled, can find those extra soft grass blades and soft twigs, being quite comfortable for a refined nest for their hatchlings. The Tree Swallow, who includes some coarser twigs, can make up in their selection of cushy feathers to keep their young nestlings comfortable.

If birds were people, we might amusingly attribute the following characters to their work:

  • Eastern Bluebirds – build with “engineering precision”
  • Tree Swallows – build with warmth and comfort
  • House Wrens – build with safety and security

 

Review of Endless Forms: The Secret World of Wasps by Serian Sumner

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Article by FMN Marilyn Schroeder

I loved Seirian Sumner’s new Endless Forms: The Secret World of Wasps and I think you will, too.

A behavior ecologist (of social insects), Sumner thinks wasps get a bad rap and wants everyone to love them the way she does. The book is both deeply scientific and a fun read.

Sumner covers wide-ranging aspects: wasp-human relationship (why don’t we like them?), wasp evolution, comparison of wasp species, solitary wasp hunting behavior, the benefits and behaviors of the social wasps, what wasps could do for us, and more.

Reading the book, I realized how little I knew about wasps and how fascinating they are. The book was published this year and includes state-of-the-art research results.

Pollinator Habitat 101 – 5-week webinar recordings

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 Photo by Dr. Jim Cane, USDA ARS Bee Biology and Systematics Laboratory, Logan, Utah.

A 5-session webinar series held from October 14th through November 11th, 2022

Find readings, links and resources for each session under the Learn With Us tab.

Doug Tallamy, University of Delaware
Pollinators’ Best Hope: A New Approach to Pollinator Habitat That Starts in Your Yard

Harland Patch, Penn State University
Creating Pollinator Gardens: The Role of Plant Choice and Design

Heather Holm, Author and Biologist
Creating and Managing Habitat for Native Bees

Matthew Shepherd, The Xerces Society for Invertebrate Conservation
Deciding To Create a Pollinator Garden Is the Easy Step — What To Do Next?

Shana Byrd, The Dawes Arboretum
Getting Started with Wildflower Patches, Flower Strips, and Meadows

All webinars were recorded and posted on the PH101 website Recordings tab.

This program is funded in part by a USDA/NIFA Integrated Pest Management Pollinator Health grant. The webinars will be presented with automated closed captions. If you wish to request traditional CART services or other accommodations, please contact Denise Ellsworth at [email protected].

Managing larger properties for birds, butterflies, and people

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Photo and article by Plant NOVA Natives

The outdoor space on larger properties in Northern Virginia, whether residential or commercial, is typically divided into formal landscaping close to buildings and natural areas at the periphery. New practices are emerging on how to manage both areas, practices that protect the ecosystem and support the birds and the butterflies while better satisfying human needs.

The natural areas between properties are an important amenity, providing visual barriers and sound buffers while capturing stormwater and reducing flooding. Looking around, it is evident that those natural areas are often being left to take care of themselves. The result is that they are steadily degrading as the native trees are displaced by invasive non-native trees and are directly killed by invasive vines. The shrubs and ground layers are equally damaged by invasives species at those levels. Many of these invasive plants originate from the landscaped areas where they had been planted before people knew to do otherwise. Preserving trees and habitat in both areas requires taking out the invasives and replacing them with native species, of which numerous options are available.

Some other tweaking is also needed to common landscaping practices. To name a few examples, piling mulch against the trunks of trees causes the bark to rot. Blowing the fallen leaves out from under trees destroys the cover where fireflies and many butterflies overwinter. Leaf blowers with two-stroke engines pour pollution into the air and are loud enough to damage workers’ ears. Outdoor lighting can adversely affect birds, insects and plants. Spraying insecticides kills the bees and caterpillars even more than the mosquitoes they are intended to target. Simple solutions are available to mitigate all these problems.

Professional property managers and community managers negotiate the contracts with landscaping companies and can work with them to adjust their services. Details of the various options for both landscaped and natural areas can be found on the Plant NOVA Trees website in a section specifically for professionals. www.plantnovatrees.org/property-managers Please spread the word to the managers of any properties where you live or work.

The Volcano Near Fairfax County

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A photograph of Mole Hill as seen along Route 33.

Article and photo by FMN Stephen Tzikas

When I travel to the Society of Amateur Radio Astronomers (SARA) annual conference every summer at the Greenbank Observatory in West Virginia, I drive along Route 33 just past Harrisonburg, VA, the home of James Madison University (JMU). It’s a rural road, but something unusual is found there – a volcano. It’s called Mole Hill, quite inactive today, but nearly 50 million years ago magma thrusted upwards to the surface through cracks in the lithosphere. The tree covered Mole Hill as seen today is made of remnants of the cooled magma column, eroding at a slower pace than the sedimentary rock around it. That resistant rock that supports the peak is a volcanic plug of olivine basalt. This basalt is dark greenish gray to grayish black, medium grained, and moderately porphyritic. Mole Hill is one of the youngest volcanoes on the east coast of North America. Mole Hill has a height of nearly 1,900 feet above sea level. Another extinct volcano, Trimble Knob, is a little closer to the Greenbank Observatory and a little farther from Fairfax County.

Dr. W. Cullen Sherwood of JMU, who passed away in 2016, gave a brief account of Mole Hill and its geology at the following link: https://csmgeo.csm.jmu.edu/geollab/vageol/outreach/fieldtrips/rockingham/molehill.html

His illustration gives the reader an idea of how Mole Hill may have originally appeared.

Mole Hill is mentioned in the Roadside Geology of Virginia book by Keith Frye. The books in the Roadside Geology Series are an excellent way to explore the geology around us when we travel along roads through different states. These books are available through Amazon.com.

 

The 2022 Butterfly Count Results from the Loudoun Wildlife Conservancy

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Photo of Crossline Skipper on Teasel by Michael Myers

Loudoun Wildlife Conservancy has coordinated the Annual Loudoun Butterfly count since 1997. The count takes place in early August, which is the peak time for butterflies in our area. They report their data to the North American Butterfly Association (NABA), which tracks butterfly populations.

This year on August 6, a typical warm, humid summer day, 60 volunteers set out to count as many butterflies as they could find in a single day. It was their 26th Annual Butterfly Count, and they tallied 3,756 butterflies of 45 species in an area of about 178 square miles in the northwestern corner of Loudoun County.

When the count day is over, team leaders tabulate their results, which are consolidated into a report submitted to the NABA. NABA collects reports from all over the country and makes them available to researchers.

Anne Ellis, Butterfly Count Coordinator, has written a very informative article, “How Does One Count Butterflies?“, in which she describes this year’s count experience and answers the question, “Exactly how does one count butterflies?”

If you would like to know which species have been seen during previous years, you can view butterfly count data and reports.  A summary report of species count by year can be viewed here. 

Take a few moments to enjoy the 2022 Butterfly Count video too.

The 2023 count will be on Saturday, August 5. Please join the Loudoun Wildlife Conservancy and count the butterflies!

Keep Our Wooded Areas Beautiful

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Article and photo by Plant NOVA Natives/Plant NOVA Trees

If your community owns some wooded common land, or if you yourself own a wooded property, you may have noticed that the woods around here have been slowly changing, and not for the better. They may still look green, but the devil is in the details: much of that “green” is now made up of invasive non-native plants that damage the ecosystem and bring down the trees.

Natural wooded areas are a beautiful and invaluable resource for any landowner or community. Unlike most material assets, they appreciate over time. They capture stormwater and keep our basements from flooding. They provide soundproofing and a visual barrier between properties as well as a place for us to walk and enjoy nature. They block the wind and lower heating costs in the winter. And of course, they are the home to birds and other wondrous beings, who will need our help if their homes are not to completely disappear.

In the past, the woods managed themselves nicely. In present-day Northern Virginia, at least some care is needed to keep the woods from degrading, turning an asset into an increasingly expensive problem. It is wise to make a forest management plan that looks ahead for twenty or twenty-five years. You can do this on your own, or you can call in a consultant to help you evaluate the situation and map out solutions to any problems. Professional assistance is available, as are volunteers from various programs including Tree Stewards, Master Naturalists, and Audubon-at-Home ambassadors.

The two biggest threats to our woods are invasive non-native plants and browsing by deer. In many places, the deer have taken away everything except the mature trees and the invasive plants, not even leaving the seedlings that should be there to become the next generation of trees. Removing the invasives and protecting native plants from deer are the highest priority in most areas.

Some of our attempts to “improve” the woods may have the opposite effect. Woods do not need to be cleaned! The dead leaves and fallen trees are essential components of a healthy ecosystem. (Dumping extra leaves from your lawn damages that ecosystem, though.) Standing dead trees provide perches for birds of prey, nesting sites for songbirds, shelters for mammals, and food for thousands of species of insects. They are also becoming increasingly rare in our human-managed environment. Try to leave them standing, or if they pose a hazard, just cut off the top and leave as much as you can standing.

For information about how to manage your woods, and how to help your community develop a long-term plan, see the Plant NOVA Trees website.

Triassic Rocks of Horsepen Run

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Muscovite mica glitter is apparent in a rock sample from Horsepen Run.

Article and photos by FMN Stephen Tzikas

Part of the Horsepen Run watershed is located in the northwestern part of Fairfax County. Horsepen Run eventually drains into the Potomac River. The trail that follows the creek in the watershed is popular with county residents. A part of the creek is also one of the regular sites of biological stream monitoring, a volunteer citizen science program managed by the Northern Virginia Soil and Water Conservation District. What a lot of people don’t know is that Horsepen Run is home to some interesting Triassic Period rocks, formed some 200 to 250 million years ago. A few years ago I participated in a geological field trip excursion as part of a NVCC 1-day 1-credit course that explored the geologic history of Mesozoic Era rift basin across the Manassas, Leesburg, and Haymarket areas. The excursion was specific to the Triassic and Jurassic Periods. Specific items of interest were the weathering of products; direction of transport; sediment structures; igneous rock textures and their cooling history, the rock cycle, and plate tectonics.

One of the sites investigated was the Dulles Access Road East “utility” off-road on the exit ramp for Rt. 28, at Horsepen Run. This site was the central point of a rift valley deep with sediments. Specifically, it was a lake bottom of red sediment. Some shale exists, breaking into sheets and fine grain. The rift was formed when the Earth

Horsepen Run creek at this location is composed of characteristic red rock: TRb Balls Bluff siltstone, both creek bottom and the adjacent 1-2 foot walls.

was pulled apart at the location. The rift valley is the linear shaped lowland between higher hilly and mountainous elevations created by the action of a geologic rift. Such valleys are likely to be filled with sedimentary deposits derived from the rift flanks and the surrounding areas. At this location the rock type contains Upper Triassic Balls Bluff Siltstone baked and thermally altered material. The red sediment at the location is obvious and contrasts with the appearance further upstream. The glitter found in the red rocks at this location are tiny fragments of mica.

In the Triassic Period, this site was tranquil and sediments came to rest. At the Horsepen Run area, bubbles on the surface of the sediment rock indicate a calcareous (calcium based) dissolved appearance where the red rock voids still have some calcium carbonate (scattered white tones on the rocks). Occasional storms brought water from outlying edges to the center and carried some coarser material. A storm deposit from the west could bring calcium carbonate from the Leesburg conglomerate. A storm deposit episode or event could last minutes to hours.

The lacustrine (lake) facies indicated an oxygen rich environment with red color clastic deposits, allowing the oxidation of the iron. This is facies evidence, referencing the look of rock to respect of environment. If there was no oxygen we would have found black shale. Low energy would have been required for the fine grain to come to rest. Fine grains could also be due to a deep environment, but here it was more likely a shallow one of 10-15 feet, where sediments could dry. This area was a cove of low energy closed lake basin water, subject to evaporation effects. Some “circle fossil” burrow tubes also exist in the fine grain clays. Burrowing organisms lived here causing bioturbation. More evidence of the oxygen rich condition is that the taphonomic conditions were not ideal for preservation, as oxygen rich area deaths led to scavenging and organic breakdown. The terraced layers at the site alternated between siltstone and claystone, caused by changes of energy due to rainfall and climate. Higher energy means more shallow depth silt: wave energy takes away clay silt by the beach. If the climate was a little dryer, the lake would shrink, alternating between shallow and deeper cycles. These climatic cycles were tied to the Milankovitch cycles of variations in the Earth’s eccentricity, axial tilt, and precession.

You also might find some of the glittery red rocks in the surrounding area near Horsepen Run. Recently I visited the EatLoco Farmers Market at One Loudoun near Dulles airport. Between the parking lot and the vendor stalls is a strip of ground, part grassy and part flat thin red rock chips, not unlike what is found at the Horsepen Run site.