Birthday Bike Trip

Frostburg Fossils

While riding the Great Allegheny Passage bike trail five years ago I passed many trailside rock layers that looked like good places to find fossils. One particular site was near Frostburg, MD where I found fossil leaves during the 2013 ride. I hoped to return there some day to hunt more fossils. This year my thoughtful daughter suggested a father-daughter bike trip on the trail from Frostburg to celebrate my birthday. It was a great idea. The trip was wonderful!

We drove to Frostburg on winding, hilly, rural roads through small West Virginia towns. The last seven miles on Interstate 68 approaching Frostburg were almost entirely uphill. Frostburg is a nice small town dating from the early 1800's with an undulating main street. It's also the home of Frostburg State University.

Our bike trip began on a cloudy cool morning. We stopped to take pictures of Frostburg's old rail station on our way to the trailhead.

Frostburg seemed to be the end of the rail line. There was a turntable just beyond the station for reversing the engines.

A twisty downhill road took us to the trailhead parking lot with its attractive shelter and informative signs.

I was thrilled to finally arrive here after years of wishing to return. Damp, chilly morning breezes made us glad we dressed properly for temperature in the low 60's.

The trail beckoned. We were soon on our way heading west toward the continental divide eight miles away.

Cool weather, the smell of fallen leaves, and trees on the verge of turning color made this autumnal equinox day feel very much like autumn. In a few miles we approached the Borden Tunnel, a relatively short tunnel only 0.18 miles long.

Our westward ride toward the continental divide was slightly uphill. Trail information claimed the maximum gradient is 1.75 percent. The gentle upgrade was definitely noticeable as we pedaled slowly along.

The next landmark was the Mason-Dixon line which forms the boundary between Maryland and Pennsylvania.

The sign pictured below explains the historical significance of the Mason-Dixon line, the "cultural dividing line between the North and the South".

Notice the brown and gold chain-like markings proceeding outward along the ground from the base of the marker above. These represent surveying chains used the mark out the border as explained in the following sign. (Click on the sign images to more easily read the text.)

We pedaled on and soon encountered enormous wind turbines. The Twin Ridges Wind Farm consists of 68 wind turbines generating as much as 139.4 megawatts of power. The next video fails to capture how big these giant structures are when viewed from the trail. They loom overhead like intimidating Martian tripod vehicles from the 2005 War of the Worlds movie.

A nice open view was available near the wind turbines.

Now we were about to enter the Big Savage Mountain Tunnel.

This impressive 0.625-mile long tunnel was completed in 1912. It's really fun to ride through. Thank goodness it's lit by overhead lamps. The exit looks a long way off!

Not far beyond the Big Savage Mountain Tunnel we arrived at our westward destination, the continental divide.

At this point we had traveled only about 8 miles from the Frostburg trailhead, but we pedaled very slowly and stopped many times along the way. The trail continues many miles further towards Pittsburgh. I knew from previous experience the next five miles beyond the westward tunnel exit shown below were not very interesting.

So we turned around and headed back out the east side of the tunnel toward Frostburg.

The return to Frostburg was now slightly downhill, and pedaling was noticeably easier. With fewer stops we were soon at the fossil hunting location I visited in 2013. Debris from the impressive layers shown in the next two pictures falls down near the side of the trail.

We explored one or two other possible locations nearby, but found the base of the layers shown above to be the best site for fossils. We spent more than an hour here searching through many fragments.

We found some nice fossils here. Some are pictured below. (Click on the images for larger, more detailed views.) This leaf was well centered on its flat stone.

The next picture shows some star-shaped leaves, probably aligned because they were part of a branch. Unfortunately, the rock is broken. The complete specimen would have been very nice indeed.

I'm definitely not an expert on the botany of extinct plants. The few books and websites I consulted to identify these fossils only confused me. I'm guessing these star-shaped leaves, called annularia, are the foliage of extinct medium-sized trees called calamites dating from 360 to 300 million years ago. We found lots of these annularia.

The annularia were often found together with other leaves.

In addition to elongated single leaves and star-shaped leaves, we also found smaller, more rounded leaves which might be from a "seed fern" called neuropteris.

We found two examples of what are apparently fossil fern seeds ("seed pods"?) called, trigonocarpus.

An online fossil image identified the next specimen, stretched horizontally on the rock, as a calamites "cone". I have no idea if this is correct.

We spent about 1.5 hours searching through rock fragments before deciding to stop. Fortunately, relatively cool temperature and cloud cover helped keep fossil hunting comfortable. We wouldn't have lasted long on the rock face in heat and full sunshine. We happily wrapped our fossils in newspaper and packed everything into a backpack. Then we cycled back to the Frostburg trailhead to eat some lunch and leave the heavy, treasure-filled backpack in the car.

We had only pedaled 16 miles at this point with many, many stops along the way, including the lengthy fossil hunting stop. Since it was still early afternoon, we decided to pedal eastward along the trail towards Cumberland, MD. By the time we had gone about 6 miles east it had become sunnier, hotter, and humid. The trail was soft and sandy in many places making pedaling harder. We started sweating in our cold weather clothes. It was time to turn around and return to the trailhead. So, after biking 28 total miles, we finished at the trailhead feeling hot, sweaty, and a bit tired.

The next day we drove back to Williamsburg through almost constant rain. In West Virginia we passed unaware through territory with good fossil hunting potential, but I didn't realize this until I consulted fossil guide books at home.  Maybe I'll get a chance to return some day. This was an absolutely wonderful trip, and I'm so very grateful to my daughter, Ellen, for suggesting it and accompanying me.

Fun With Light

Polarized Light

I recently purchased a sheet of polarizing filter material so I could play with polarized light and show the effects to my granddaughter, Sophie.

Light propagates through matter by causing electrons within matter to oscillate. Electrons absorb light and oscillate as a result. Oscillating electrons then emit light. Light transmission proceeds through a series of absorption and subsequent emission events by one electron after another along the path of transmission. Molecules in the polarizing filter have a structure such that electrons can oscillate in one direction, say up and down, much, much easier than they can oscillate in a perpendicular direction, say side to side. When unpolarized light, oscillating in all directions, propagates through the polarizing filter, up/down oscillations get through much, much easier than side to side oscillations. Light exiting from the polarizing filter is, therefore, oscillating almost entirely in the up/down direction, and, thus, becomes mostly linearly polarized in the up/down direction. 

I found my laptop screen to be a good source of white light. For example, a blank new file in Microsoft Notepad looks like the first image below.

I probably should have known beforehand that laptop screen light is polarized, but I discovered it with the polarizing filter. The next image shows a piece of polarizing filter held so it lets laptop light through.

The next image shows the filter rotated 90 degrees, completely blocking light from the screen. So, laptop light is linearly polarized!

Next, I tried the well-known procedure of placing various plastic objects between the polarized laptop light source and a polarizing filter. I thought Sophie would like seeing how colors appeared like magic. For example, the next image shows an ordinary empty tape dispenser placed between the computer screen and the polarizing filter.

Next, I tried the bottom of a plastic McDonald's cup.

Sophie said, "Cool!" I was thrilled that she liked it! But what causes the colors? The light source is white, and the polarization filters alone don't cause colors to appear. It must be caused by the properties of the plastic items themselves and how they interact with polarized light.

The colored plastic material is birefringent. This means the internal molecular structure creates asymmetric conditions for the propagation of polarized light. (In other words, electrons can oscillate more easily in one direction than another.) In one particular polarization direction, say the x-direction, light travels fastest through plastic. If light is polarized in the y-direction, perpendicular to the x-direction, it travels slower through plastic than light polarized in the x-direction. This is equivalent to saying the index of refraction varies with polarization direction.

When polarized white light from the laptop enters the plastic it encounters molecular asymmetries mentioned above. Some component part of the incident polarized white light encounters regions where it travels fast, and some other component part encounters regions where it travels slower. The components get out of step and finally emerge combined from the plastic with an overall different exit polarization direction than the entrance polarization direction. The change in polarization direction depends on the wavelength of the light, therefore different colors change polarization direction by different amounts. So when we view the plastic object through a polarization filter that would block polarized laptop light, we don't see blackness. Instead, we see a range of colors where different wavelengths of white light have changed their polarization direction by different amounts.

I tried several other items with mixed results. Some looked very nice, like this protractor from my old college drawing kit.

The (broken) circle template was also interesting.

This French curve drawing tool was nicely colored.

I rummaged around the house looking for other plastic candidates. An old cassette tape case produced a good result.

Would an old CD case also show colors? Yes.

How about the plastic lid to a bathroom Q-tip dispenser?

I tried an empty sliced ham container.

The last item of this type was the cylindrical plastic tube of an "energy stick".

Colorful effects can also be achieved with overlapping clear "scotch" tape segments. Sophie and I enjoyed making some of these by placing tape strips on a clear plastic sheet. Fortunately, we had the kind of tape that works. I've heard some types of tape don't work. Different tape thicknesses change polarization directions by different amounts depending on wavelength, so wonderfully colorful arrangements result.

When the polarizing filter in front of an overlapping tape arrangement is rotated a nice kaleidoscopic effect results.

All these effects are well known. There's nothing new here except the fun we had when my granddaughter saw these for the first time.