Final Project Phy103

.docx

School

Western Governors University *

*We aren’t endorsed by this school

Course

103

Subject

Geology

Date

Dec 6, 2023

Type

docx

Pages

Uploaded by alasmith32

1 7-2 Final Project Milestone: Geologic Analysis. PHY-103 Earth System Science Southern New Hampshire University

2 I. Executive Summary This report will detail the geology, climate, and landscape findings regarding the proposed subdivision in the area of Walterville, Oregon. The area of the proposed subdivision is in an area with many features. These include geologic features, possible tectonic activity, volcanic activity, flooding, and heavy precipitation. First, I will detail the geologic features in the area, including soil stratigraphy and soil profiles. This information will help to decide where would be the best location for the subdivision. The topographical features in the project area have the potential to cause flooding and erosion in the proposed subdivision. This report will detail the creation of these features and how they will affect the project area. There is evidence of tectonic activity within the project area, which may cause concerns in the future. Finally, I will discuss the climate and weather in the area. The project site is located in an area prone to heavy precipitation, which can cause flooding. This information must be considered when deciding where the subdivision should be placed in the project area. II. Geology The rock types present in the project areas stratigraphy and cross-section in order from the surface down are limestone (A), sandstone (B), granite (I), limestone (C), coal (D), siltstone (E), coal (F), sandstone (G), and schist (H) (Bergmann, 2011). The first layer, limestone, is a biochemical sedimentary rock and is mostly comprised of calcite (C a CO 3 ) (King n.d-a.). Sandstone is a clastic sedimentary rock and is made up of mainly quartz and clay (GeoKansas, n.d.). Granite is an intrusive igneous rock, meaning that it is formed deep within the earth from

3 cooled magma rock (Lutgens et al., n.d). Like limestone, coal is also a sedimentary rock. Unlike limestone, it is an organic sedimentary rock made up of once-living organisms that have been compressed rock (Lutgens et al., n.d). Schist is the last of the rock types that are present within the project area. Schist is a foliated metamorphic rock that has shale as a parent rock (King, n.d- b.). Sediment is usually deposited in layers, with the bottom layers being the oldest and the top layers being the youngest. There are exceptions to this rule in the form of dikes and sills. Dikes are incongruous areas that form in the rock layers from magma that is forced upwards through the sediment layers (Lutgens et al., n.d). Sills are horizontal areas, the result of magma that finds weak spots in rock structures (Lutgens et al., n.d). The oldest sediment layer is schist. The schist layer is at the bottom of the stratigraphy, located underneath the other layers. Even though granite is underneath the schist, it is a younger rock due to its presence throughout the layers and into the sandstone layer B (Bergmann, 2011). The next oldest layer is sandstone, then coal, siltstone, coal again, limestone, and sandstone, as they are located above the bottom layer. Layer A is limestone and the youngest layer due to its location at the top of the other layers (Bergmann, 2011). Limestone is usually formed in warm, shallow saltwater but can be formed in lakes and hot springs as well (Basics-Depositional Environments, n.d.). Sandstone generally forms in basins both near and far from water after minerals are washed down and compacted over time (GeoKansas, n.d.). Limestone and sandstone are layered together in the stratigraphy, meaning that they were formed in or around water. Siltstone is found near rivers and streams that weave through floodplains. Schists are formed when shales and sandstones are subjected to heat and

4 compression (King, n.d-b.) Coal is found in areas that are damp and abundant in plant debris (Lutgens et al., n.d). The included soil profiles give insight into the potential for erosion ( Final Project Soil Profiles , n.d). Soil profile A has four horizons. The first horizon, O, is made up of organic matter. Horizon A is next and is made up of topsoil, B is subsoil, and C is the substratum, which is weathered or poorly weathered rock ( Soil Horizons - Soil Ecology Wiki , n.d.). Horizon O is not always present in soil profiles. The occurrence of this horizon means that at some point, organic matter covered the topsoil. Soil profiles B and C do not have an O horizon. This could be due to glacial movement or changes in the boundaries of streams and rivers ( how parent material affects soil profile development , n.d). The project area is in the Cascade Range. Soil and sediment have been moved from higher in the Cascades down to the project area, causing different profiles ( How parent material affects soil profile development, n.d). The topological map of the project area shows many streams and rivers, creating the possibility of flooding. The stratigraphy shows two layers of limestone, which indicates that the area has flooded before (Basics-Depositional Environments, n.d.). In years with high precipitation, the likelihood of flooding increases exponentially. The project area is located within an area with a known thrust fault as well as a volcano. The thrust fault is visible on the site stratigraphy and cross-section as well as on the topographical map ( Final Project Stratigraphy and Cross Section, n.d). Thrust faults are found in subduction zones, meaning areas where the lithosphere (crust and upper mantle) is sinking back into the mantle. Earthquakes at thrust faults occur due to severe compressional stress (Lutgens et al., n.d). The presence of a fault in the project area opens the possibility of earthquakes. These earthquakes may be small, but there is a chance for a larger earthquake to happen. There is a

5 volcano in the vicinity as well ( Final Project Walterville Topographical Map , n.d-d). While it is unlikely that the volcano itself will erupt, it is possible that an earthquake could cause magma to be forced to the surface, causing fires or destruction of the subdivision. The project is also in a floodplain, surrounded by rivers and streams. This can bring the possibility of flooding. III. Streams and Tectonics There are multiple topographical features seen on the map of Walterville ( Final Project Walterville Topographical Map , n.d-d.). These features are all related to the stream processes that have occurred in the region and include drainage basins, divides, stream channels, valleys, floodplains, and oxbow lakes (Lutgens et al., 2021). Drainage basins, also known as watersheds, are formed when surface water from precipitation is moved downward into low-lying areas (Lutgens et al., 2021). Drainage basins are bounded by imaginary lines called divides. In some instances, a divide can be seen as a ridge above a drainage basin. In other instances, the divide may be harder to see due to smoother topography (Lutgens et al., 2021). The water that collects at the bottom of drainage basins joins with other bodies of water to create streams and rivers. Drainage basins are seen in multiple areas of the project site topographical map ( Final Project Walterville Topographical Map , n.d-c ) , the most relevant being where the proposed project site is located. Streams either create alluvial channels or bedrock channels depending on the type of material the stream is flowing through (Lutgens et al., 2021). Alluvial channels are created when streams flow through loose sediment. These channels are capable of changing considerably, as it is easier for the stream to erode, move, and deposit sediment. Oxbow lakes are formed when an alluvial channel meanders over time and eventually encounters hard material, causing erosion to slow (Lutgens et al., 2021). An oxbow lake is seen on the Walterville topographical map, just south of Camp Creek Road ( Final Project Walterville Topographical Map, n.d-c). This causes

Your preview ends here

Eager to read complete document? Join bartleby learn and gain access to the full version

Access to all documents
Unlimited textbook solutions
24/7 expert homework help