Landslides RYAN TERRY GEOGRAPHY 1000 E-PORTFOLIO FALL 2015

What is a landslide?  Definition: The downward sliding of a relatively dry mass of earth and rock. (Dictionary.com)  The term landslide includes a wide range of ground movement such as rock falls, deep failure of slopes, and shallow debris flows.

Effects on the Environment  Destroys the slope/hill  Eliminates all vegetation  Buries houses and sometimes entire villages  Weakens the slope and makes it more susceptible to further landslides.

The Gros Ventre Slide During the 1920’s several small earthquakes shook areas of Teton County. On June 23 rd, 1925, Earth, Rock, and Debris moved rapidly from an altitude of 9000 feet. This event lasted only minutes, but a river was dammed and the landscape was changed forever. Photo Credit: John H Boyd III.

Primary factors of the slide. 1. Heavy rains and rapidly melting snow saturated the sandstone, causing the shale rock layer to become exceptionally slippery. 2. The Gros Ventre River, cutting through sandstone, produced a free slide with no extra support holding it in course. 3. Swampy pools with no outlets, on top of the mountain, indicating water- saturated soil. Photo Credit Penn State College of Earth and Mineral Sciences

Lower Slide Lake Debris Field/Natural Dam Gros Ventre Slide brought down 50 million cubic yards of debris from the south side of the Gros Ventre canyon. The slide moved 2100 vertical feet, while traveling 1.5 miles. The debris field was 2,000 feet wide, 225 feet deep at the river, and climbed 350 feet up the opposite north side of the canyon. This huge amount of earth formed a natural damn is the Gros Ventre river that formed Lower Slide Lake Photo Credit TetonWyo.org “Land Slide”

Jackson Hole Land Slide 2014 A damaged home sits atop a slow moving landslide on East Gros Venture Butte in Jackson Wyoming. Photo Credit La Times “ Wyoming town 'cowboys up' to deal with landslide threat ”

 Human activity has contributed to the East Gros Ventre Butte landslide that has displaced nearly 60 residents and cost taxpayers at least $750,000.  The area around the slide has been the site of grading and construction over decades.  Most recent activity was the construction of a new Walgreens last year. The pharmacy sits directly below an arching crack in the butte.  There was also a 200,000 gallon water leak at the house above the pharmacy in Photo credit: Jackson Hole News and Guide 2014

Snake River Landside Water can act as a lubricant, causing already unstable layers of earth to succumb to the forces of gravity and begin moving down hill. Earthquakes can shake up and disturb layers of soil causing them to become unstable and move downhill. Add high amounts of precipitation to the mix and you can get an effect known as liquefaction. This takes place when loosely packed, and water logged sediments near the ground surface lose their strength in response to the ground shaking. Photo of the Double-Draw Landslide, courtesy of Civil Air Patrol

Snake River Slide Time Lapse 2011 Wyoming Department of Transportation time lapse video shows a massive mudslide at Snake River Canyon. (courtesy/WYDOT)

How to protect yourself:  To begin preparing, you should build an emergency kit.  A collection of basic essential items your family may need in the event of an emergency. This should be able to get you through 72 hours.  Do not build near steep slopes, close to mountain edges, near drainages, or natural erosion valleys.  Discuss with your insurance agent about coverages for landslides if you live in a susceptible area

Recognize the Warning Signs!  Changes in landscape.  Doors or windows stick or jam for the first time.  Outside walls, walks, or stairs begin pulling away from the building.  Underground utility lines break.  New cracks appear in plaster, tile, brick, or foundations. One landslide can cause other landslides, flash flooding due to the loss of vegetation on slopes, damage to gas and power lines, Plus disrupt other utilities such as sewage making areas uninhabitable. Wait until authorities check the area and say it is safe before returning.

Works Cited  /stelprdb pdf /stelprdb pdf  / /  unty/grading-may-have-caused- slide/article_bbad5ba abd8- 7ff2ae790f8c.html unty/grading-may-have-caused- slide/article_bbad5ba abd8- 7ff2ae790f8c.html  drive-landslide/image_905d902c-be54-50f9-8ead- 3c61823af31f.html 