PHY 103 Final Project

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Jan 9, 2024

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Preliminary Report of Environmental Findings 1 Preliminary Report of Environmental Findings Chylah M-M. True Southern New Hampshire University (SNHU)

Preliminary Report of Environmental Findings I. Executive Summary: This report means to offer a fundamental report of the geological and environmental discoveries for the proposed Walterville, OR project site. This report will briefly discuss any tectonic risks, such as presence of fault lines, potential plate movement, and resulting seismic or volcanic activity in the area, as well as climate concerns, including an analysis of hazardous storms, precipitation, and temperature considerations for the development site near Camp Creek Cemetery. The geological analysis will also include an analysis of the soil profiles for the proposed sites. The site’s proximity to Mount Jefferson poses the most obvious threat. This stratovolcano has erupted 8 times in its history, with 1 eruption occurring every 613 years. The volcano has been dormant for 631 years, making it past due for another eruption. Additionally, this region is susceptible to large-scale earthquakes. This location is at risk for another large earthquake, with the most recent high-magnitude quake occurring over 85 years ago and occurring on average every 85 years. A significant risk exists from massive waste events and flooding. With a recurrence interval of 9.8 years, high magnitude rainfall has been observed. Area C’s soil and location make it vulnerable to rapid erosion during these kinds of events, and the location of areas A and B put them at risk of flooding from the river nearby. In order to reduce potential losses in the future, these risks require special attention if development is to proceed. II. Basic Geology: Limestone (layers A & C) is a biochemical sedimentary rock formed by the breakdown of coral, algae, and shells as well as animal waste. Calcite, a type of calcium carbonate is what makes up most of this. The limestone demonstrates that when layers A and C were shaping, there

was a waterway or freshwater lake at the site, or it was essential for the ocean bottom. Sandstone (layers B & G) is a detrital sedimentary rock that forms when quartz or calcite, organic material, or other minerals were compressed together with sand-sized particles left over from the weathering of rocks. Sandstone indicated that deposition from lakes, rivers or the ocean floor is present. Coal (layers D & F) is a fossil fuel and organic sedimentary rock that forms when plants are kept from decaying in low-oxygen environments like swamps and then buried in the sediment and compressed and compacted over time in warm conditions. The presence of coal indicates that the climate at the time these layers were formed was swampy. Siltstone (layer E) is a detrital sedimentary rock that structures in a similar style as sandstone, except rather than sand- sized particles, it is made through the compaction of residue measured particles and is usually ruddy or grayish in variety. Siltstone demonstrates that there was once a delta or glacier around the area. Schist (layer H) is a foliated metamorphic rock that forms when long, flat minerals are put under extreme pressure, heat, and chemical activity (Lutgens, et al. 2021). A slate step and a phyllite step must be used to transform schist. After the schist forms, it may change into gneiss if it is subjected to additional extreme pressure. The schist in the area demonstrates it is on the continental side of a convergent plate boundary. Granite (layer I) is an intrusive igneous rock that forms when molten material cools and hardens inside the Earth’s crust for a millennial or more (Lutgens, et al., 2021). The formation of large, visible mineral crystals found in granite is made possible by the passage of such an extended amount of time. It is for the most part made of quartz and feldspar which are reinforced through heat with different materials. Granite is a sign of an underground magma chamber and a subduction zone, where continental rocks are melting. Andesite (volcano & vent) is an extrusive igneous rock that typically occurs in thick lava flows produced by stratovolcanoes. Andesite indicates that a stratovolcano has erupted in the region,

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resulting in andesitic lava flows and a subduction along the Juan de Fuca and North American plates in the development site that gave rise to the Cascade Range. With the utilization of relative dating, we can decide the time period for when each layer was shaped corresponding to different layers in the stratigraphy. In figure 1, we can see that the layers framed from the oldest to the youngest are H (Schist), G (Sandstone), F (Coal), E (Siltstone), D (Coal), C (Limestone), B (Sandstone), I (Granite), A (Limestone), and then volcano and vent (the Andesite bedrock) being the youngest as the fault does not affect the vent. We know that the granite dike, layer I, is younger than all but layer A because it cuts through the other layers, indicating that they had already formed, whereas layer A was formed later and is the youngest because it was not cut by it. We can see that the fault that runs through the cross-section formed last because it cut through all of the layers after A formed. Layer A formed the fault, which is a reverse strike-slip fault. As the fault moved the rock layers up on the right, layer A eventually eroded, leaving no trace on that side of the fault and a smaller, more eroded layer B serving as the top layer. With the exception of the granite layer, all have horizontally flat horizons. The stone layer expelled vertical from the center, while different layers above it were framed by different measures of strain over significant stretches. Layers G and H could have formed simultaneously because the weight of the long, flat minerals caused by the pressure of the sandstone allowed the schist to form. Swamp-like circumstances probably won nearby for an extensive stretch after the sandstone frame, which is confirmed by the rehashing layers of coal in the cross-segment which structures from plant matter lowered in low oxygen conditions and is then compacted with tension by weighty silt layers. We can see that a thick layer of siltstone formed on top of the first layer of coal. This indicates that the sediment on top was very fine-grained and probably contain

clay or mud. One more layer of coal shaped, this time with sediments that would have been comprised of natural matter like green growth, coral, and shells as the following layer to frame was limestone. The arrangement of limestone as the following layer shows that the oxygen levels probably rose to have upheld the endurance of such natural matter from submerged organic entities. The subsequent formation of a layer of sandstone, probably as a result of deposition in the body of water, and a subsequent layer of limestone at the top point to the continued existence of organic underwater organisms at the time. A granite dike cut through the rock layers at some point prior to the formation of this final limestone layer. A fault event took place sometime after layer A was formed. After the issue framed, there was a huge disintegration that happened on the part of the shortcoming which was raised on the right-side causing layer A to be totally eroded and a piece of layer B to dissolve as well, representing the more modest layer B on the right of the fault. The fault and the volcanic vent are the geological features that may have the greatest potential of having a devastating effect on the subdivision or overlying neighborhood. If the fault slips again, the earthquake that follows could kill or damage infrastructures. It is important to keep an eye out for activity at the nearby volcanic vent. Sinkholes “are common where the rock below the land surface is limestone, carbonate rock, salt beds, or rocks that can naturally be dissolved by groundwater circulating through them” as a result of the presence of the layers of limestone in the region (Water Science School, 2018). In soil profile 1, there is a slightly thicker layer of mineral topsoil and there is a layer of organic soil (O). Below layer A is a thicker layer of an accumulative mineral zone (B), followed by a larger layer of parent material (C) before the thin layer of the bedrock located at the bottom. Soil profile 2 has a much thinner layer of natural material (O) at the top alongside a skinnier

layer of topsoil. The subsurface mineral layer (B) is a lot closer to the surface and is just marginally more modest than Profile 1. The parent material (C) is comparative in size to profile 1 and takes up almost 2/3 of the profile with just a smaller quantity of bedrock present than in profile 1. Profile 3 has a thin layer of organic material that is decomposing at the top (O), there is no layer A, and layer B has been severely eroded, leaving only a slight layer that is almost exposed and only slightly thicker than layer A in profile 2. Due to the erosion of layers A and B, Horizon C is comparable in size to profile 1, but it is significantly closer to the surface. The majority of this profile is bedrock. Because the bedrock is so prominent in each profile and is so close to the surface in some of the profiles, there is very little room for excavation. Additionally concerning, is the presence limestone in the stratigraphy because limestone can be dissolved by groundwater stated above, resulting in the development of spaces, underground caverns, and sinkholes (Water Science School, 2018). Bedrock close to the surface, the recently active fault system, and these soil profiles with so much erosion in the cross section all make these 3 locations unsuitable for subdivision development. III. Streams: The topographic map suggests that stream processes and associated erosion could account for lots of the geographical land features. While the project site is close to the McKenzie River, glacial erosion is likely to have a significant impact on many of the valleys near Mount Jefferson and Mount Washington. The McKenzie River cuts its way through the land starting at Clear Lake on the western side of Mount Washington before joining with Willamette River near Eugene. East of the project site, deep, steep valleys have been created by erosion caused by the McKenzie River. Deep valleys with a relatively straight down cut are found at the river’s head.

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However, the terrain becomes flatter and closer to the base level as the river moves west. The floodplain becomes relatively flat here as the area widens and the river winds its way through it. The river’s downcutting closer to its baseline allowed it to meander and slowly erode side to side creating the floodplain. The Walterville Canal borders the floodplain that gives way to higher-elevation areas on the northern side of the project area. Development projects in the marked areas A and B would be threatened by rising floodwaters based on historical data of river elevation rise above gauge. The soil may deteriorate over time and become unsuitable for construction due to erosion caused by frequent flooding of the river. As the stream rises and immerses the floodplain, it would both store and strip silt soils, as well as saturate effectively dissolve the basic bedrock. Sinkhole mitigation should be emphasized when considering development in this area due to the possibility of its formation. The elevation difference between the areas marked A and B on the topographic map, which reduces the risk of river flooding, and the location of the area marked C could put it at risk for rapid erosion due to high precipitation events washing down the slope and removing sediments. Area A is also located at the bottom of a mountain, which could trigger landslides if the McKenzie River were to overflow due to flooding in the valleys. IV. Tectonics: The proposed development’s proximity to Mount Jefferson, a potentially active stratovolcano, and the fault that runs through the Walterville topographic map are some pretty obvious tectonic elements in the development area. Subduction along plate boundaries result in these tectonic formations. An oceanic-continental convergence boundary occurs when the continental crust of the North American plate meets the oceanic Juan de Fuca plate. Lithospheric material is partially melted as a result of the oceanic plate’s denser material being subducted

beneath the lighter continental crust. There are volcanic eruptions and the formation of continental volcanic arcs like Mount Jefferson’s Cascade Range as a result of the rock melting because it becomes less dense and can eventually force its way to the surface (Lutgens, et al., 2021). Plate tectonics are also responsible for the fault that runs through the proposed development area. Pressure builds up in the crust as the North American plate shifts above the mantle and interacts with other plates. After accumulating sufficient pressure, slippage eventually results in an earthquake (Lutgens, et al., 2021). The fault poses a significant threat to the proposed development area, as shown by historical data. In the past, this fault has been the site of 7 earthquakes with magnitudes greater than 6.0 on the Richter scale. Two of the quakes that were recorded had a magnitude greater than 7.0, making them major earthquakes. Another quake of that magnitude could result in fatalities and billions of dollars worth of damage to the region, depending on the scope of the construction project (Lutgens, et al., 2021). The possibility of a 6.0 or greater magnitude should be taken into consideration when planning the development due to the 85-year interval between each fault event and the last recorded earthquake. Even though Mount Jefferson’s volcanic eruption’s likelihood of occurring relatively soon is much lower than that of a powerful earthquake along the fault, it should still be taken into consideration. The data indicates that Mount Jefferson has erupted 8 times in the past 5,000 years. One eruption scored a 6 on the Volcanic Explosivity Index (VEI), which is comparable to the Pinatubo eruption of 1991 (USGS, 2016). The historical record contains two VEI 5 eruptions of a magnitude comparable to that of the Cascade Range’s own eruption of Mount St. Helens in 1980. A second eruption of this magnitude could have an impact on the area around Mount Jefferson, posing a threat from lahars as glacial melt moves through the deep valleys formed by

the regions river system. Even though eruptions typically occur every 1,000 years, there are some instances in the record when they occur much less frequently. Planning a development within the volcano’s range should be taken into account that the most recent eruption was a VEI 4 eruption roughly 631 years ago. V. Weather: The average annual temperature mean for the region is roughly about 54 degrees. The average annual precipitation means for the region is approximately 3.0 inches. The average temperature monthly varies by the season. In the winter (December-February) the average temperature monthly is about 43 degrees. The average temperature in the spring (March-May) is about 51 degrees. The average temperature in the summer (June-August) is 67 degrees. And the average temperature in the fall (September-November) is 56 degrees. The monthly precipitation values depend on the season as well. In the winter the average precipitation is about 4.3 inches. The average precipitation in the spring is 2.8 inches. The average in the summer is 1.6 inches. And the average in the fall is 3.5 inches. The seasonal variation in precipitation shows that the rainfall was the highest in the winter averaging at about 4.3 inches as stated above with the highest month being November at 5 inches. The summer months on the other hand are the lowest in precipitation averaging at about 1.6 inches with the driest being July at 1.2 inches. The polar front theory states that mid-latitude extratropical cyclones form on boundaries between warm and cold air. Cyclogenesis, or the strengthening of a low-pressure center when warm tropical air and cold air masses converge in the middle latitudes, is what causes mid-latitude cyclones. As cold fronts move through the region, showers and thunderstorms are likely, according to the climograph data. Winter brings the most precipitation, but temperatures never drop below freezing, even when the mean minimum is considered. As a result, blizzards and other winter

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type storms are unlikely. Some of the thunderstorms can be pretty severe and can result in serious weather conditions such as hail, lightning, and tornadoes. Volcanic eruptions are another potential hazard in the development area. Another type of natural hazard that is common in this area are landslides. Landslides are amongst the most widespread, chronic, and damaging natural hazard in Oregon (Oregon.gov, n.d.). Though the volcano has not erupted in a long time, there is still a chance it may (USGS, n.d.). With volcanic eruptions being one of the higher risks in Oregon, a landslide is more likely to happen and cause severe damage. According to the historical weather data, the maximum precipitation event in the record was November 2, 1917 with precipitation at 12.09 inches. The type of storm that likely produces this amount of precipitation was a mid-latitude cyclone. The mid-latitude cyclone brought in low pressure with a mix of warm and cool air converges resulting in a cyclogenesis. The cyclogenesis created thunderstorms, bringing extreme levels of precipitation. The location is not frequently subject to large storms. The development site does have a pretty high rainfall amount slightly under every 10 years (which to me isn’t really that frequently). A simple recurrence interval of extreme precipitation events would be calculated through R=(N+1)/O with R=Recurrence intervals in years, N=Number of years recorded, and O=Occurrences at the project site. For this data, there was a 97-year time frame with 10 occurrences recorded. We now plug in our numbers and solve the equation R=(97+1)/10. This equation predicts that a similar amount of rainfall will occur approximately every 9.8 years at the projected development site. Despite the fact that the data provided for the proposed development site indicates that severe weather does not occur frequently in this area, flooding is still a possibility. The site is situated at the base of a mountain and a level beyond a floodplain which demonstrates

conceivable gamble of flooding due to the past data for the region. Additionally, the area’s active drainage basins may increase water discharge from the basins, putting the proposed development site in significant danger of flooding, mudslides, and erosion. VI. Analysis of Findings: The proposed project raises a few concerns because of the risks associated with this location. It is impossible to ignore the possibility of substantial tectonic activity. Concerning is the location’s proximity to Mount Jefferson, which is statistically overdue for another eruption. In the event of an eruption, pyroclastic flows, lahars, earthquakes, and ashfall all pose significant threats to life and property. Over the course of the past 600 years, the location has experienced 7 significant earthquakes. It is past due for another tectonic event, as it experiences an average of 1 large earthquake every 85 years. Fires, significant structural damage, and power outages can all be brought on by earthquakes. The projected development site’s location being in a floodplain increases the likelihood of flooding during heavy precipitation. Areas A and B could suffer losses such as fatalities, structural damages, and bedrock erosion that would result in sinkholes in the event of an inundation of the floodplain. Area C would be actively eroded by high-magnitude precipitation events, which are common in this region, potentially leading to mass wasting. The risk is insignificant in comparison to the costs of developing this location. Tectonic, flood, and erosional hazards have the potential to reduce profits and offset financial gains in this region.

References Department of Land Conservation and Development. (n.d.). Natural hazards. Oregon.gov. https://www.oregon.gov/lcd/nh/pages/natural-hazards.aspx#:~:text=Chronic%20hazards %20include%20river%20and,on%20steep%20slopes%2C%20or%20windstorms . King, H. K. (n.d.). Limestone: What is Limestone and How is it Used? Geology.com. https://geology.com/rocks/limestone.shtml Lutgens, F. K., Tarbuck, E. J., & Tasa, D. G. (2021). Foundations of Earth Science (9th ed.). Pearson Education (US). https://mbsdirect.vitalsource.com/books/9780135851616 The Editors of Encyclopedia Britannica. (2023). Fault Geology. Britannica. https://www.britannica.com/science/fault-geology USGS. (n.d.). Volcano Hazards Around Mount Jefferson . USGS. https://www.usgs.gov/volcanoes/mount-jefferson/volcano-hazards-around-mount-jefferson USGS. (2016). Volcano Hazards Program Glossary - vei . USGS. https://volcanoes.usgs.gov/vsc/glossary/vei.html Water Science School. (2018). Sinkholes. USGS. https://www.usgs.gov/special-topics/water- science-school/science/sinkholes#overview

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