Due to the inclement weather, our last stop was Veach Gap but not without a couple of stops along the way. The next few stops were along skyline drive. The first stop was basalt feeder dikes that you can see from the image below. Strike and dip are also shown.
The next image was taken at Sandy Overlook showing deformed tension gashes. Fingers (courtesy of Callan Bentley) showing the sense of movement. The Alleganian Orogeny was most likely the culprit for the deformed tension gashes.
After a few stops along Skyline drive, we finally made it to Veach Gap. Not sooner after we started hiking, did Mother Nature decide it was time for some rain. Luckily I learned my lesson a few weeks, so I was well equipped this time. After the class and myself threw on our rain gear, we stated making our way towards the outcrop.
Veach Gap, which is located within Massanutten Mountain, is part of the George Washington National Forest. What makes this place so unique is the amount of anticlines located within this area. While hiking around the outcrop we noticed the rock was composed of quartzite. The anticlines within this location have been were a result of the Alleghanian Orogeny, which took place Roughly 300 million years ago. During the Orogeny, Africa was slamming into ancestral North America which is how the rocks got folded.
While out in the field, I interpreted this fold as upright/gently plunging using the Fleuty diagram.
Using the limb measurements from above, I was able to come up with the trend and plunge of the axial hinge. The intersection point gives us a trend of the axial hinge 33° with a plunge of 7° .
During our class field trip, we came across one of the best primary structures I have ever seen (seriously). These primary features are known as columnar jointing. This feature formed during the rifting of Rodinia, which took place roughly 750 million years ago. This formation is above the previously visited Swift Run Formation.
While Rodinia was rifting, the basalt lava was flowing to the surface cooling quickly. As the basalt loses heat it contracts in volume equally across the flow surface. Arrest lines are present as they run perpendicular to the surface. This end product results in a feature known as columnar jointing which looks similar to mud cracks. The columnar jointing has a polygonal shape with all angles equaling to 120°.
As you can see from below, the angles from the Limberlost Trail do not equal 120° nor do the sides equal. This suggests that the columnar jointing underwent deformation at some period in time. The sides themselves averaged around 9.3 cm in length. We will keep this in mid when we measure the sides of the columnar joints at Compton Peak.
While at the location we took strike and dips of the columnar jointing.
Even though this is not geology related I thought I would share a picture of a male American Redstart that my professor noticed. Also “Redstart” is capitalized according to the Integrated Taxonomic Information System.
After we left the Limberlost Trail, our class headed towards Compton Peak which wasn’t to far away. We made sure while at Limberlost we took good notes so we could compare with Compton’s Peak, which is another outcrop of columnar jointing.
The first thing I noticed when I came upon Compton Peak, was the condition of the columnar joints. These had undergone less deformation then the previous outcrop. The only way to make sure of this was by taking some measurements. The first thing we did was measure the angle between the sides. Most of the angles that we measured were close to 120°. In addition the size of the columns were much larger then the Limberlost Trail. The average side for the Compton’s Peak jointing were 40.4 cm which is around 30 cm size increase when compared to Limberlost. Presuming that both outcrops were formed during the same period, deformation from past orogenies must have had an greater effect on the Limberlost Trail columnar jointing when compared with Compton’s Peak.
Once we left Garth Run we made our way to the next destination, which was the Swift Run Formation. I must have been very lucky because some people ended up with tics as we made our way back to the van after seeing this outcrop. We had to walk roughly a mile through brush to get to this location, but I must say it was well worth it. This location has some great primary and secondary features. While at Swift Run we were able to determine if these beds have been overturned or if they were right side up. The image below shows an outcrop from the Swift Run Formation.
Swift Run Formation is above the basement complex but below the Catoctin Formation. The rock types we noticed were arkosic sandstone and a meta-mudstone. This formation is very patchy and is not found in all locations above the basement complex. In a few select locations, you’re able to find the Catoctin sitting right on top of the basement complex. This would suggest that in the past we had some type of local relief at the time Swift Run was being deposited. Swift Run ends up filling in the valleys but left the hilltops unburied, and later the Catoctin erupted over both formations.
Sediments from this location were a result of when the supercontinent Rodinia was breaking up around 600 million years ago. The breaking up of the supercontinent created a rift valley that is very similar to what we see in East Africa today. The depositional environment for these sediments was most likely a rift valley due to the abundance of feldspar. Feldspar tends to weather pretty easily so we know these sediments were close to its source area. The sediments from the highlands are able to get trapped in the lowlands. I drew a figure below to represent how the feldspar can get trapped within these rift valleys.
While at Swift Run we took some measurements and noticed some primary/secondary features. The first one is the result of my classmate David Brooks, he showed me this cross-bedding . Cross-bedding is a great way to determine if the beds have been overturned. As you can see from below, the beds have not been overturned.
Another primary feature I came across is known as mud clasts. During times of higher energy, the sand is able to rip up mud from the lower energy environment.
Another feature that caught my eye was this piece of float that my professor found. It shows graded bedding and also a sharp contact between the bedding.
The secondary features that I happened to come across had undergone tectonic activity. Evidence of this was prevalent throughout the formation. Here is a nice S-fold that we stumbled upon.
Another way we determined that these beds were not folded over was by taking measurements of the cleavage and bedding. If the cleavage is dipping steeper then the bedding, them the bedding is in its correct position. The strike and dip of the beds were 355°,07°, while the cleavage was 065°,34°.
The next day we made our way to the Limberlost Trail columnar jointing in which we compared with the Compton Peak jointing.
So a few weeks ago my structural geology class headed out into the heart of Shenandoah for a weekend of camping and geology. The trip was supposed to last 3 days but due to Mother Nature, we had to cut the trip short. It’s actually a good thing we did because the following day, Skyline Drive was covered with 4 inches of snow. Now getting back to the geology; during our trip we noticed many structural features and took various types of measurements with our compasses. One of the first stops on our trip was the Garth Run high-strain zone, which is located within Madison County, Virginia.
The rocks exposed along this outcrop ranged from porphroclasts-bearing protomylonites and mylonites. These rocks are from the mesoproterozoic aged basement complex, which are located at the bottom of the sequence. Multiple mountain building events helped shape the fabric of Garth Run outcrop. Some of these rocks were over a billion years old.
The story of Garth Run begins with the mountain building event known as the Grenville Orogeny, which is named after Grenville, Canada. Just as fast as the Greenville Orogeny took place, they eventually eroded away over time. Once eroded, sediments and lava piled on top of what was left of the basement complex. Then the next Orogeny known as the Alleghanian, takes place and these rocks get metamorphed. The Alleghanian Orogeny took place between 200-300 million years ago, in which Africa slammed into the east coast of North America (or did we slam in to them). The stresses from the Orogeny concentrated into discrete zones, known as shear zones. Hence, Garth Run shear zone.
A shear zone is basically a deep fault that takes place beneath the earth. Under these conditions, rocks tend to be ductile rather then brittle. On average if the shear zone is beneath 15km then the rocks will undergo ductile deformation. This process can create a unique rock known as mylonite, which comes in 3 grades. At Garth Run I inferred 2 rock types as ultramylonite and mylonite.
The mylonite below displays a well developed S-C fabric.
The image below displays an asymmetrical porphyroclast that has gone under deformation due to the tectonic activity from the Alleghanian Orogeny.
The next image is of a boudinage. This structure occurs when a when a tabular unit is stretched due to stress. The tabular unit can be either igneous or metamorphic.
The next stop on our trip was the Swift Run Formation.
So a couple of years ago I wrote an op-ed in regards to why bottled water is unsafe and the environmental effects from it. While I was doing my research for the op-ed, it had occurred to me that the bottled water industry is a bigger problem then most people think. Since then this topic has been on my radar for a while, I thought I would share it with everyone. Also if you like to learn more regarding the subject, here is a link to the move trailer “Tapped” http://www.youtube.com/watch?v=72MCumz5lq4
The Bottled Water Industry: wrong on so many levels
In a society where we are trying to go green, many people are unaware of
the effects of drinking bottled water. I myself am guilty of drinking
bottled water and then not recycling the bottle; it’s easy to believe one
bottle isn’t going to make much difference. However, that one bottle does
make a difference, from start to finish. The bottle water industry is
depleting our water, filling our landfills, and burning fossil fuels at an
enormous rate. Bottled water companies across the country are stealing our
natural resource and selling it back to us for a high price. I pay $15 a
month for my tap water and can use as much as I want. We now live in a
world where gas is cheaper then bottled water, and yet we complain about
Plenty of consumer industries mislead us into believing the benefits of
their product outweigh the cost of environmental impact, or we simply don’t
think about it at all. The water bottle industry has done an amazing job
of selling us a product that we already pay for. The Beverage Marketing
Corporation estimated that Americans spent $10.8 billion on bottled water
in 2009, which accounted for over 40 billion plastic bottles. Apparently
only 20% of these bottles get recycled. Roughly 40 million water bottles a
day make it to the landfills.
Not only is the recycling of these bottles an issue but also the oil used
in producing bottled water. First we need to make the bottle in which we
use oil refineries, they make the petroleum. Roughly 47 gallons of oil are
used in the production of 38 billion plastic water bottles according to the
Pacific Institute. On average 2.5 million tons of carbon dioxide is emitted
annually into the atmosphere as a result of the production of plastic water
bottles. Think about how much carbon dioxide we could remove from the
atmosphere if we stopped drinking bottled water altogether. Not only do we
need oil to make bottled water but we also need water. It takes 3 liters
of water to produce one liter of bottled water. It seems so senseless that
we are wasting that much water when there are places in the world that
don’t have access to clean water. Not to mention climate changes and
impending droughts. Every year I hear of more severe droughts but
apparently this doesn’t affect the bottled water industry’s thirst for
A clear case of this involves the Nestle Company. This company was pumping
out the groundwater to the point where mudflats were showing up and streams
were running dry within Mecosta County, Michigan. Even in years of
droughts, the company was allowed to pump water even though residents were limited to usage. It’s estimated that Nestle pumps roughly 218 gallons a
minute from the ground just from that one well and they have sites all
across the country. Even today the residents of Mecosta County are still
fighting the Nestle Company. This is not only happening in Michigan but all
over the world. You would think the government would have laws to protect
us from this.
Amazingly, as large as the bottled water industry is, there is only one
person from the Food and Drug Administration actually regulating this
industry according to the Natural Resource Defense Council. We have more
regulation over municipal tap water then we do bottled water. The FDA
states that bottle water companies are exempt from submitting annual
reports on what takes place at the water mining plants even though
municipal tap water plants have to. FDA also states that if the water is
bottled and sold within the same state lines then water quality testing is
exempt. Many studies are coming out showing contaminants have been found in bottled water; Fiji water is a great example of this. A few years back they
had on their label “The label says Fiji because it’s not bottled in
Cleveland”. Well the Cleveland water resource mangers took offense and did
there own testing of Fiji water. They found 6.3 micrograms of Arsenic per
liter in the Fiji brand. The NRDC tested over a 100 brands of bottle water
and found contaminants in 55% of the brands.
We need better laws to protect our groundwater and the recycling of plastic
bottles. We have so many laws when it comes to oil, but not many when it
comes to water. Without water we have no life on earth. Only six states
have laws relating to the recycling of water bottles, we need more states
to jump on board. With populations continuing to rise in the future, it’s
essential that we conserve our water for future generations. We as
individuals can start now by reducing the amount of bottled water we
consume. If we stop buying it, they will stop supplying it. Bottled water
is essential for disaster relief but not for everyday consumption. We can
start using re-useable water bottles and recycle when we do buy. Most
importantly we need laws to prevent bottle water companies to mine water.
I’m not saying I will never drink bottled water again but I guarantee I
will think twice before I do.
I also thought I would throw in this table from the Natural Resources Defense Council report on bottled water
Cooley H, and Gleick P (2009) Energy implications of bottled water, Environ Research Letters 4(1): 1-6
Gleick PH (2004) The myth and reality of bottled water.. In The world’s water 2(24): 17–43
Olson E (1999) Bottled Water: Pure Drink or Pure Hype? Natural Resources Defense Council (NRDC). New York
Shermer M (2003) Bottled twaddle: is bottled water tapped out? Scientific American. 289(1): 33-35