Milestone Two

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Southern New Hampshire University *

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103

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Geology

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Dec 6, 2023

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Emily Durkin PHY 103- Lynda Folts 9/24/2023 Milestone 2: Streams and Tectonic Analysis This report presents the results of several areas identified as sites A, B, and C, in the geological survey. The landscape in these areas demonstrated features of stream processes. This survey analyzed data from topographic maps, historical data on earthquakes and volcanoes, and how the tectonic plates change the landscape at sites A, B, and C. The goal of this report is to present landscape features, how they were formed, and potential hazards that could affect human development. Landscape Features: The three project sites are located near an active subduction fault 60 miles from the Mount Jefferson volcano, which last erupted around 15,000 years ago, during the last major glaciation. Mount Jefferson is Oregon’s second highest peak at 3,201 meters or 10,502 feet. The largest explosive eruption from Mount Jefferson caused ash to travel as far as southwest Idaho. Oregon’s landscape has been shaped by eruptions, flooding, earthquakes, and glaciers. Project site A is situated in a flat flood plain area along the McKenzie River with the highest stream discharge in January and December. Project site B is south of Site A. Site B is in a

hilly region located near the fault associated with the Cascadia Subduction Zone near the coast of North America. This Subduction Zone is on a divergent plate boundary between the Juan de Fuca plate and the North American plate. Site C is in a mountainous area north of sites A and B. This area has a make up of igneous, metamorphic, and sedimentary rocks. Site Analysis: Site A: Project site A is relatively stable, although there are some major geological hazards. The meanders are prone to flooding which leads to sediment erosion and deposits in point bars. This can change the river’s course and could end up forming oxbow lakes. The sediment deposits could change the rivers’ depth and flow. This could affect the water’s quality and destroy aquatic habitats in the area. The survey noted a large amount of rainfall at the beginning of the year. The max rainfall was 19.84 inches, and the average river elevation was 34.11 feet in January. This could have submerged animal farms, killed crops, and overall caused suffering to the people living in this area. Site B: The hills in this area are the result of tectonic activity. These hills and mountains developed due to the Juan del Fuca Plate and the Noth American Plate converging. This process is known as subduction. Subduction occurs when one tectonic plate moves underneath another tectonic plate. Site B is vulnerable to mudslides, landslides, and soil erosion because of its deep slopes and heavy rainfall. Site C: This site is in a mountainous area north of the river at site A. These mountains are a mix of sedimentary and igneous rocks such as granite. These rocks are formed from the solidification of magma or lava about 60 million years ago. The mountains in this area are a result of tectonic activity, that being uplift and soil movement caused by the fault in the area. Site

C is vulnerable to landslides, rockfall, and erosion due to the river systems, heavy rainfall, and steep slopes. Fluvial Features and Tectonic Landscape Analysis: Project sites A, B, and C have floodplains and rivers running through them. These waterways are not only a crucial habitat for wildlife in the area and are important to keep the environment thriving, but they are also an important part of the local culture and source of recreational activities for the people living in the area. These waterways have shaped the landscape over time, which has resulted in different fluvial features such as valleys, canyons, and floodplains. Site A: The stream the runs through site A has created a floodplain through meandering. The stream eroded the surrounding land and deposited sediment on the floodplain, thus creating a fertile area. A river on a floodplain could produce another floodplain at a lower level after a drop in the base level. This relative drop in base level is characterized as stream terraces. The formation of terraces happens when a stream flowing on thick alluvial deposits adjusts to a relative drop in base level. During heavy rainfall, the stream can overflow and cause erosion, which can be a potential hazard for any human developments in the area. Site B: The river in project site B meanders and creates a steep cut bank. Over time the cut bank is eroded, making the river wider and shallower. This is illustrated in the remains of an oxbow lake that the river once flowed through. The erosion can lead to sediment buildup and destruction of aquatic habitats. Site C: In the mountainous area of site C, a river has created a valley through the process of downcutting. It eroded the surrounding mountains to create a flat and wide valley. This is why

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site C would be the best area for human development. However, measures need to be put in place for safety as site C’s steep slopes and unstable soil could lead to landslides. The river in this area is prone to flooding, which could also be a hazard to any human development. The tectonic activity in the area can impact the locals and could potentially be a risk to their survival. Structures in the area may end up with structural damage due to the fault. The process of liquefaction, which is when an earthquake turns loosely packed water-saturated soil into liquid, in flood zones and landslides may damage nearby residential areas. In order to manage the risks, a few measures should be implemented in these areas of development. These measures are emergency response teams being trained for natural disasters, monitoring for signs of activity at the volcano and fault line, earthquake resistant buildings, and evacuation plans for volcanic eruptions and floods. Another important measure to implement would be early warning systems to alert the public in case of a natural disaster. Conclusion: In conclusion, sites A, B, and C all have their own set of unique landscapes and tectonic features as well as hazards to human development. The plates are constantly moving under the earth’s surface and could cause a natural disaster at any moment. The subduction fault is the biggest tectonic hazard in the area; however, site A is the least suitable area for human development as it has a high risk of flooding and the potential for earthquakes and volcanic eruptions. These hazards are why it’s important to study the landscape, understand the geological risks, and to appropriately plan for any potential natural disasters. Managing potential risks will save lives.

References: Earthquake hazards program . Earthquake Hazards Program | U.S. Geological Survey. (n.d.). https://www.usgs.gov/programs/earthquake-hazards Oregon Department of Geology and Mineral Industries . Oregon Department of Geology and Mineral Industries : Oregon Department of Geology and Mineral Industries : State of Oregon. (n.d.). https://www.oregon.gov/dogami/pages/default.aspx NASA. (n.d.). Mount Jefferson . NASA. https://earthobservatory.nasa.gov/images/82396/mount- jefferson Geology and history for Mount Jefferson . Geology and History for Mount Jefferson | U.S. Geological Survey. (n.d.). https://www.usgs.gov/volcanoes/mount-jefferson/geology-and- history-mount-jefferson Snhu-media.snhu.edu. (n.d.). http://snhu- media.snhu.edu/files/course_repository/undergraduate/phy/phy103/phy103_final_project_ historical_data.docx Snhu-media.snhu.edu. (n.d.-a). http://snhu- media.snhu.edu/files/course_repository/undergraduate/phy/phy103/phy103_final_project_ historical_data.docx Login. (n.d.). https://view.officeapps.live.com/op/view.aspx?src=http%3A%2F%2Fsnhu- media.snhu.edu%2Ffiles%2Fcourse_repository%2Fundergraduate%2Fphy %2Fphy103%2Fphy103_final_project_historical_data.docx&wdOrigin=BROWSELINK YouTube. (2017a, April 26). Phy-103: Continents Adrift - an introduction to continental drift and plate tectonics CC . YouTube. https://www.youtube.com/watch?v=Wl_eF85xWd4 National Geographic. (2021, May 3). Explore plate tectonics . Science. https://www.nationalgeographic.com/science/article/plate-tectonics

Milestone Two

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