Title

Distribution of Pleistocene Terraces

Date

5-30-2013 9:15 AM

Location

Health and Wellness Center (HWC) Room 105

Department

Earth Science

Session Chair

Jeff Myers

Session Title

Earth Science Senior Seminar Research: Geological Hazards Impacting US 101 at Beverly Beach, Oregon, and their Mitigation

Faculty Sponsor(s)

Jeff Myers

Presentation Type

Presentation

Abstract

The Pleistocene terraces along the Oregon coast are the foundation for parts of U.S. highway 101 between Yaquina Head and Beverly Beach State Park, Oregon­. The goal of this study is to identify the geological dangers of constructing the highway on top of these terraces, in order to understand how they are affecting the road. It is my hypotheses that Highway 101 is subject to slumping in areas where the road was built on the unstable terrace foundation. To test this hypotheses I will map out the distribution of terraces in the Beverly Beach area.

As the beach erodes, the waves cut back into the coastline, producing a terrace, which then can be preserved on the land as a result of tectonic uplift or from changing sea levels, which occurred during the multiple glacial and interglacial periods during the Pleistocene. As many as five to seven terrace levels occur on other parts of the coastline, such as those found around Coos Bay. Near Beverly Beach these unconsolidated terraces overlie the Miocene Astoria formation.

The stratigraphy of the terraces along Beverly Beach suggests that these terraces are slumping towards the ocean. This slumping is likely due to the sediments within these terraces. When these sediment layers become saturated with water it causes the area to be unstable and prone to slides. This is a result of high porosity and permeability along with the presence of expansive clays.

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May 30th, 9:15 AM

Distribution of Pleistocene Terraces

Health and Wellness Center (HWC) Room 105

The Pleistocene terraces along the Oregon coast are the foundation for parts of U.S. highway 101 between Yaquina Head and Beverly Beach State Park, Oregon­. The goal of this study is to identify the geological dangers of constructing the highway on top of these terraces, in order to understand how they are affecting the road. It is my hypotheses that Highway 101 is subject to slumping in areas where the road was built on the unstable terrace foundation. To test this hypotheses I will map out the distribution of terraces in the Beverly Beach area.

As the beach erodes, the waves cut back into the coastline, producing a terrace, which then can be preserved on the land as a result of tectonic uplift or from changing sea levels, which occurred during the multiple glacial and interglacial periods during the Pleistocene. As many as five to seven terrace levels occur on other parts of the coastline, such as those found around Coos Bay. Near Beverly Beach these unconsolidated terraces overlie the Miocene Astoria formation.

The stratigraphy of the terraces along Beverly Beach suggests that these terraces are slumping towards the ocean. This slumping is likely due to the sediments within these terraces. When these sediment layers become saturated with water it causes the area to be unstable and prone to slides. This is a result of high porosity and permeability along with the presence of expansive clays.