A Landslide in Pikeville EarthCache

This Earthcache will take you to a pull off area on US 23, from the coordinates listed above you can see where several landslides have occurred over the years, & also see what the state highway department has done to mitigate (prevent) future landslides.

This slide is located on US 23 just South of Pikeville and many people pass by here everyday and never realize just what is located on the other side of the safety fence. So let's learn about landslides. Note: There is the potential of falling rocks at any time. There is no requirement to venture behind the safety fence. If you choose to inspect this area,please wear appropriate protection including a hard hat, safety shoes, gloves and safety glasses.

What is a Landslide?

A landslide is a geological phenomenon which includes a wide range of ground movement, such as rock falls, deep failure of slopes and shallow debris flows. Although the action of gravity on an over-steepened slope is the primary reason for a landslide, there are other contributing factors affecting the original slope stability. The term landslide includes a wide range of ground movement, such as rock falls, deep failure of slopes, and shallow debris flows.

Landslides are caused when the stability of a slope changes from a stable to an unstable condition. A change in the stability of a slope can be caused by a number of factors, acting together or alone. There are 2 main causes of landslides: natural and human.

Human causes include vibrations from machinery or traffic; blasting; and earthwork which alters the shape of a slope, or which imposes new loads on an existing slope.
Natural causes include groundwater pressure acting to destabilize the slope; Loss or absence of vertical vegetative structure, soil nutrients, and soil structure; and weakening of a slope through saturation by snowmelt or heavy rains.
This slide was most likely caused by a combination of both human and natural causes. Those being blasting, as a result of when US 23 was being constructed, and absence of vertical vegetative structure.

What Types of Landslides Are There?
According to the USGS, the term "landslide" describes a wide variety of processes that result in the downward and outward movement of slope-forming materials including rock, soil, artificial fill, or a combination of these.

The most common types of landslides include:

SLIDES: mass movements, where there is a distinct zone of weakness that separates the slide material from more stable underlying material.

FALLS: Falls are abrupt movements of masses of geologic materials, such as rocks and boulders that become detached from steep slopes or cliffs

TOPPLES: Toppling failures are distinguished by the forward rotation of a unit or units about some pivotal point.

LATERAL SPREADS:
Lateral spreads are distinctive because they usually occur on very gentle slopes or flat terrain.

Landslides constitute a major geologic hazard because they are widespread, occur in all 50 states and U.S. territories, and cause $1-2 billion in damages and more than 25 fatalities on average each year.

Located behind the safety fence you will see the side of a small ridge that has been cut away to make room for the road. During the process of making room for the road explosives were placed into bore holes, and the subsequent blast fractured the rock. The broken pieces were cleared away, leaving the rock face you see now. Do you see the various layers, or strata, visible in the rock face? You will also notice the layers are tilted towards you.

Mitigating A Landslide

In order to prevent (or mitigate) a landslide, one might use one or more of the following actions:

. avoiding construction on steep slopes and existing landslides,

. stabilizing the slopes.

. create a retaining structure, e.g. safety fence, retaining wall, etc.

Here you can see the safety fence that has been constructed. The fence is designed to stop the debris that might fall from a landslide. Although a catastrophic failure of the hillside could not be stopped by such a fence, the occasional boulder and rock debris that does fall is easily stopped at the fence. This prevents the rock from landing in the roadway creating a serious traffic hazard.

Logging Requirements:

1. Post a photo of you and your GPS while you are at the posted coordinates with the landslide area in the background.

2. What do you see that might fall or slide off of the rock surface?

3. Which of the five landslide types listed above do you think might occur here?

4. Name at least two safety items that should worn or used when investigating a potential landslide area?