Geology Home work!! Essay on Oregon Dunes Field trip...

Detailed Geological Trip Report

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Detailed Trip Report: First Part 7:45 a.m. We departed from Campus. We drove north on Highway 101. As we continued north through the Highway, we passed through Yachats, a town that is approximately 75 miles. Just on the left past the Adobe Motel was the turn-off to Smelt Sands Beach which was our first stop. ( that’s all copied) Stop 1: Smelt Sands Beach. Smooth and brown rocks are molded together by wet beach sand. The sand is, however, coarse with contents including, quartz, basalt, shell pieces, serpentine and agates. The rock forming the base rock formation is present in the sand signifying the rock is broken down by erosion. Different rocks are also exposed and are believed to be from the Cenozoic Era. They are featured as part of the Yachats Basalt and are Late Eocene (36-40 million years) in age. These rocks were formed as a result of the cooling of magma from a series of eruptions ( this is all copied from that cheater essay.. not hard to tell see I told you… KEEP This I will alter (Alt and Hyndman 1978). There is the existence of a Pleistocene terrace where the town of Yachats is built. The terrace was probably formed when the sea level was lower, and its deposit is 10,000 to 1.8 million years old. It cuts into the Yachats basalt sequence (Snavely, 1980). Its present level, which is above, the present sea level, is attributed to either the rise of land due to tectonic activity or dropping of the sea level. It is, however, difficult to know where the uplift of the land is possible in such an active coastline. The Smelt Sands Beach is located to the South of the start of Yaquina formation. A basalt flow is found at this spot. It lies beneath the Pleistocene terrace. This basalt is about 40 million years old. The Pleistocene, on the other hand, is about 1.8 years old. What happened between the formation of the basalt and the Pleistocene is not known yet. However, some researchers speculate that land movement could have occurred which led to dropping of the sea level or rising of the land. The whole town of Yachats has been built on this beach terrace. Information about the town of Yachats indicates that much is of it occurs in a zone that prone to tsunami if another Cascadia subduction occurs. The part of the town, which is not, in the tsunami zone is found on the hillside. However, this part also risks destruction from the tsunami-causing earthquake. Studies carried out by researchers indicate 50m of beach would retreat in this region should a cascadia subduction occur (Snavely, 1980). This means that the biggest part of the Yachats town would be destroyed considering that most of the premises in the town, which include shops, hotels and residential houses are within a distance of 50m from the water. Plants found in this region include bog anemones and gold-eyed grasses. Stop 1a: Cape Perpetua-Heceta head area. There is a trail down the Devils churn at the end of the low road. The existence of local vents in the Cape Perpetua-Heceta head area is the primary sources of basalt in here. They formed shield-like accumulations composed of sub aerial basalt which were initially erupted on a shallow shelf (Snavely, 1980). This explains why basalt is the most common type of rock in Oregon (Alt and Hyndman, 1978). We departed Smelt Sands Beach Stop 2: Darlingtonia Wayside ( move this up to the top as a unplanned stop in the morning , it actually was our first stop) as I told you many of times just begin the paper with this as Our first stop of the morning was actually an unplanned stop at the Darlingtonia Wayside) The next stop was at Darlingtonia Wayside, which is on the north of Florence. Here, we saw a grove of Darlingtonia Carlifornica. Darlingtonia is the only land in the state of Oregon that has been set aside for the purpose of protectijng a single plant species. The species that have preserved here is the cobra lily also known California pitcher plant. This plant is carnivorous. It grows in acidic and nutrient deficient soils. This makes it thrive well in harsh conditions where most plants cannot (Alt and Hyndman, 1978). This has made to receive very little competition from other plants. The plant was thick and healthy, and the environment seemed to suit it well. The plant derives its nutrients from trapping insects. It does this by enticing the insects into the pitcher-shaped hollows created in its leaves. Once the insects are in the chamber, they fall to the lower end of the hollow and drown. The plant, using bacteria, breaks down the insect and this provides it with nutrients. This is an adaptive feature of the plant that helps it to compensate for the lack of nutrients in the soil. The Darlingtonia Wayside is covered with sand. In areas where the cobra lily grow, the sand is covered with mud and organic material. The high level of sand in this region is mainly due to its closeness to the beach Stop 3: Strawberry Hill. This area has interesting erosional patterns as compared to any other area. We observed a series of basalt intrusions that run parallel to each other. Another noticeable formation was running near the path leading down to the beach and down the length of the hill. Regular and brick-like shapes formed the surface of this formation arm of the ocean cuts through this basalt flow. ( this is all copied ) As much as these flows look like sills (igneous body that intrudes parallel to existing rock layers), they are dikes (feature that cuts across the preexisting rock layers). Both the sills and dikes are flat and igneous intrusions to rocks. The sand in this place is dark and fine-grained most probably because it is wet. Shell midden, which are remains, of shellfish is caught and shelled by the natives and not that uplifting of a fossil bed lie around this area. Stop 4: Heceta Churn ("Devil's Elbow"). The erosion of a fault in flows of the Yachats basalt is responsible for the formation of the churn. Basalt and silica-rich basaltic rock form the dikes in this area (Snavely, 1980). Huge and visible basalt formations that were earlier attached to the mainland were separated when erosion of the softer rock around the stacks occurred. The sand in this area is black since it may be composed of basalt. Black sands in these regions are said to contain minerals such as, garnet zirconium, small gold deposits, titanium, platinum, chromium and iron (Snavely, 1980). A small igneous intrusion as compared to that at Strawberry Hill runs down into the water. The basalt formations cooled slower on the inside but faster on the outside hence gas was released (Carver, Clague & Darienzo, 1997). This explains the large vesicles of the basalt formation on the dikes. Stop 5: Heceta lighthouse 21 km from Yachats town on the south, we came to Heceta lighthouse. The lighthouse is about 17 m tall, and our tour told us that the beam of light emitted from the lighthouse is visible for a distance of about 34 km. this makes it, the strongest light, found on the Oregon Coast. The Oregon Parks and Recreation department are mandated with the maintenance of the lighthouse. According to our tour guide, ( we don’t have a tour guide as stated several times… its our professor )and we didn’t go up to the light house we researched Devils Churn and Elbow and the large Seastack instrusion that was there at the site .) the lighthouse has a long history. He told us that it got its name from a Spanish explorer known as Bruno de Heceta. Heceta explored the Pacific Northwest in the 18th century. Our tour told us that, before him, the place where the lighthouse is located was used a popular spot for hunting and fishing by the native tribes, who were found in the region. The natives hunted the sea lions and gathered bird eggs. In 1888, white people moved into the region and occupied the surrounding land. The lighthouse was constructed in the year after approval of the US lighthouse service (Alt and Hyndman, 1978). The lighthouse underwent a number of repairs and renovations since its construction, the latest repair being in 2011. The lighthouse remains a significant feature in the Heceta region. Stop 6: Sea lion caves (we didn’t stop directly at the sealion caves.. we stopped south of it as stated in the intinerary to look at the North Far end begginnngs of the Sand Dunes) The next stop after the Heceta lighthouse was at the sea lion caves. The sea lion caves are located about 18 km on the north of Florence. The sea lion caves are a system of caverns and sea caves, which open to the ocean. The caves are at sea level, and this makes them be washed continually by ocean. The main cavern of the system has about 2 acres in of floor area and a rock dome which is about 38 m high. On the south of the main chamber, a passage runs for about 300 m to an opening to the sea. Our tour informed us that this passage is normally flooded during high tides while, in low tides, it lacks water. The entrance on the western part of the chamber is a high passage. A third entrance to the cave system is found to the north of the main chamber and is about 15 m above the ocean. This entrance serves as an observation area because it is elevated. One is able to view the whole underground cave system together with the animals found in it from this point. The common plants found in these caves are lichens and algae, which cover the walls of the caves and caverns. Our tour guide told us that this system of caves was discovered by a seaman known as Captain William Cox in 1880. After discovering it, Cox returned to caves several times to explore them. It is reported that, on one, occasion, he was stranded for several days in the caves because of a rough ocean and stormy weather, and he survived starvation by shooting and eating the meat of a sea lion. It is not known whether the story is authentic. However, what is certain is that Cox eventually purchased the land around the place in 1887 (Snavely, 1980). The sea lion caves from the largest system of caves in the world and they offer an awe-inspiring view of sea lions. The caves are home to sea lions from which they derive their name. the sea lions occupy this place mainly during winter months. . Stop 7: Oregon Dunes After Darlingtonia Wayside, we headed to Honeyman State Park. (as stated we didn’t stop at honeyman state park )At this site, we were able to view sand dunes. The Honeyman State Park provides an excellent from which one can get a magnificent of dunes. We then went to the Oregon dunes overlook where we commenced our search for yardangs. Since none of us knew what yardangs are, we left wondering whether it was an animal or plant. However, our tour guide led to a long dune and pointed out a yardang, which was sitting on top of the dune. It turned out, control to our guesses, a yardang is a geological formation. Yardangs normally form when new dunes form on top of others, which are already in existence. Yardangs are features formed from the action of winds on dunes. When wind erodes an older underlying dune, the newer dunes form on top of it migrate. This erodes the older dune. If the erosion continues, the older dune wears out until the only thing that remains from it is the core, which is normally hard to erode (Carver, Clague & Darienzo, 1997). This remaining part is what is referred to as the yardang. Our guide informed that, in Oregon, yardangs form only in winter. This is because moisture is needed to hold the sand forming the dunes together. Stop 8: Eel Creek Campground Our adventure of exploring dunes continued as the day went by. After driving for about 30 minutes, we came to the Eel Creek Campground where we continued to explore and study dunes. We explored one dune in this area and like before, I decided to measure its size. I used the first astronomy method, which involves using a combination of estimates of length and right-triangle trigonometry. I walked the lengths of the dune and counted the steps I made, and this helped me estimate the dune’s height. From my estimates, the height of the dune was about 68 feet. This was down from 86 feet that had been achieved from the visit by other explorers. This indicates that the dune has been wearing out presumably from erosion. From my estimations, I found that the dune’s angle of elevation was 27 degrees, which was also, a reduction from 34 degrees that had been achieved earlier. This further supported the theory that erosion of the dune has been taking place (Browning & Gallob, 1999). These comparisons may not be accurate because of the estimation which could have had huge effects on the calculated values. However, since the same method was used in both instances, it offers a near accurate picture of what could have been happening in terms of action of wind on the dune. After the exploring the dune and measuring it, we moved a few metres on the north and came to a small flat plain. This plain had dry and light sand on top of wet and dark sand. The wet sand shows the water table in this region. it shows the lowest point of a dune, and this explains why it is flat. However, our guide informed that these lowest points are not permanent as the dry sand found on top of the wet sand has the capability to grow into dunes. This will, therefore, shift the minimum point to another place. According to studies, the water table we discovered in this region is very crucial because it is the main source of water for the Bay-North Bend region. As of 1987, the aquifer supplied about 5 million gallons of water per day to this region. The water table in this region sometimes expresses itself as a lake on the dune (Carver, Clague & Darienzo, 1997). This normally shown in the formation of a lake in the middle of a dune with the lake having no inlet. This shows that the source of the water is from below in the water table. This dune was also characterized by the presence of yardangs on top of it. The yardangs had formed humps on the dune. However, they did not have a certain definite appearance. Stop 9: Horsfall Beach Our last stop on this trip was at the Horsfall Beach. The beach is characterized by miles of open, inland and beach dunes and flooded plain wet lands. Some of common activities common in this region include surf fishing, hiking, horseback riding, and vehicle riding. This beach is famed as a training ground for the running legend Steve Prefontaine and a site for a shipwreck that occurred in 1999 (Snavely, MacLeod, Wagner & Lander, 1980). Winter storms are common in this region and are responsible for the numerous shipwrecks that have occurred here in the past. We carried out an experiment at the site to determine the speed of the offshore drift. Our simple experiment involved throwing an orange into the water at a distance of about 100 feet from the shore. Our aim was to observe the amount of time the orange took to reach the share so that we can calculate the speed by dividing the distance by the orange with time taken to reach the shore. Our assumption was that the orange would travel in a straight line to the shore and this would make it easy to calculate the speed of the offshore drift. However, this was not the case because other factors came that affected the movement of the orange. The first one was that the in the first few minutes, there was a strong wind blowing to the shore and this made the orange return to the shore very quickly. Another problem was the direction the wind pushed the waves. This made the orange drift to the south for about 20 feet each time it returned. At the point, the orange failed to come to the shore and remained in the sea. In addition, each time the orange made it to the shore produced different results and it was hard to find an average. This is because the disparity recorded was so big. All the same we calculated the velocity and found an average of 15cm/s. however, when we tried to compare our results with those of other groups that have performed the same experiment at a site, we realized that the disparity between the results was so big. This made it hard to compare the results and come up with an average value. This caused mainly by the complexity of the currents system in this region. Studies indicate that offshore currents at this place have a speed of about 13cm/s. however, they can reach about 150 cm/s to 200 cm/s when currents, tides, and wind are pushing in the same direction (Snavely, MacLeod, Wagner & Lander, 1980). From this beach, we boarded the bus and went back to school.

References:

Alt, D. D. & Hyndman, W. D., (1978). Roadside Geology of Oregon. Mountain Press.

Browning, M. & Gallob, J., (1999, March 20). Clearcut's Role Questioned in Highway Failure.

News Time. Retrieved from http://www.newportnewstimes.com/1999/nt_news1229/general/nt_news-04.html

Carver, G., Clague, J., & Darienzo, M., (1997). Estimates of Coastal Subsidence from Great

Earthquakes in the Cascadia Subduction Zone, Vancouver Island, Washington, Oregon,

and Northern most California. Department of Geology and Mineral Industries.

Snavely, P. D., MacLeod, N. S., Wagner, H. C. & Lander, D. L., (1980). Geology of the West-

Central Part of the Oregon Coast Range. Department of Geology and Mineral Industries.