Geology is Everywhere! Come to Chattanooga to discover an Earthcache.
Overview
This is an EarthCache and has no physical container. It is intended that you read the cache description including information about Landslides. You then visit the actual location, make observations, and eventually send the cache owner your answers to the questions below. If you have any questions, please reach out to me.
This EarthCache can be completed while standing on the public sidewalk. There is no reason to go to the base of the landslide, and certainly no reason to climb on or near the slide area. Do not attempt this from your car. Park next door, and walk over here.
Logging Requirements
- How is a mudslide different from other types of landslides?
- Comparing the site as you see it now against the historical pictures, what changes have occurred over the years?
- Is there any evidence of recent mudslide activity? Do you believe a future mudslide could occur here?
- Upload a photo of yourself (or a personal item) at ground zero and attach this photo to your log.
History
The main road up to Signal Mountain here (now known as Highway 127) was completed in 1912. When originally constructed, the road was much narrower, but as traffic increased, the road was widened, including further widening to allow local businesses to be built here along the side of the road. The oldest nearby structure was a restaurant built in 1930. While the actual date that the structure that once stood here is unclear, it was in place on the earliest street view image that I could locate in 2007.
In February 2019, things changed. After a week of heavy rain, a heavy mudslide at this location occurred early on a Saturday morning, washing the Subway restaurant away.
April 2017 image:
February 2019 image:
May 2019 image:
June 2021 image:
June 2023 image:
January 2025 image:
Introduction to Landslides
Landslides occur in all 50 states, and can affect lives, property, infrastructure, and the environment. A landslide is defined as the downslope movement of rock, soil, and debris under the influence of gravity. While gravity is the primary driving force, other factors, such as water saturation, earthquakes, or erosion, can trigger a landslide.
The stability of a slope is a balancing act between two opposing forces: driving forces, which push material downhill, and resisting forces, which hold it in place.
- Driving Forces: The main driving force is the weight of the slope material itself. As the slope's angle increases, this driving force becomes stronger.
- Resisting Forces: These forces are determined by the strength of the slope material and the friction between its components. Water can significantly reduce these resisting forces, while the root systems of vegetation can increase them by binding the soil together.
What is a Mudslide (or Mudflow)?
Mudslides or Mudflows are a type of landslide, often with a rapid movement of rock, earth, and other debris saturated with water. The key ingredients of a mudflow are water and soil. They develop when the ground becomes saturated, such as during heavy rainfall, or rapid snowmelt, or during a volcanic eruption, changing the earth into a flowing river of mud or “slurry.” A slurry can flow rapidly down slopes or through channels and can strike with little or no warning at avalanche speeds. A slurry can travel several miles from its source, growing in size as it picks up trees, cars and other materials along the way. The mudslide here caused a partial collapse of the hillside including trees and other vegetation that came down the hill and caused the building to collapse.
Sources:
Historic street view images @ Google, 2017, 2019, 2021, 2023, 2025.
News story: Mudslide Washes Away Subway Restaurant At Foot Of Signal Mountain; Nearby Employee Says: "It's Gone"; Flooding Closes Numerous Roads - Chattanoogan.com
“Backgrounder: Landslides and Mudflows” by FEMA LANDSLIDE/MUD
“Landslide Basics” by USGS Landslide Basics | U.S. Geological Survey
“The Landslide Handbook – A Guide to Understanding Landslides” by USGS The Landslide Handbook - A Guide to Understanding Landslides | U.S. Geological Survey
