Post on 24-Feb-2016
description
Atrani, Amalfi Coast, Italy
MUDSLIDE IN CALIFORNIA 2014
Landslides, Southern California
Photo Credit: USGS
Slumps
Images (c) 2002 and 2005 Andrew Alden, licensed to About, Inc. (fair use policy)
Avalanches
Images (c) 2002 and 2005 Andrew Alden, licensed to About, Inc. (fair use policy)
Photograph by Marc Muench/Getty Images: http://environment.nationalgeographic.com/environment/natural-disasters/avalanche-profile/?source=A-to-Z
Rockslides
Spectacular rock fall in Yosemite photographed by Herb Dunn on August 6, 2006. http://geology.com/articles/yosemite-rockfall-hazards/
MASS MOVEMENTS
Mass Movements Downslope movement of soil & weathered
rock by force of gravity Climatic conditions determine extent of mass
movements Occur on slopes
Mass Movements Factors influence mass movements
Material’s weight Material’s resistance to sliding or flowing
Depends on: (1) amount of friction, (2) how cohesive the material is, (3) anchored to bedrock or not
Trigger Earthquake
Water Rainfall increases weight of soil
Types of Mass Movements Creep
Slow, steady, downhill flow of loose, weathered Earth
Few cm per year Noticeable over long periods of time
Causes trees to tilt, crack in walls
Types of Mass Movements Flows
Thick liquid Move as slowly as few cm per year or hundreds
of km per hour Mudflows
Swiftly moving Mixtures of water and mud Triggered by earthquakes Common in volcanic regions
Heat melts snow on slope & fills into spaces in sediment
Lahar Occurs after a volcanic eruption
Semi-arid regions - intense rainfall, little vegetation
Types of Mass Movements Slides
Rapid Occurs when a relatively thin block of soil, rock,
& debris separates from the underlying bedrock Landslide Rockslide
Slump Occurs from a landslide Leave distinct crescent-shaped scars on hillsides
Types of Mass Movements Slides
Avalanches Landslides with snow Radiation from sun melts surface snow Refreezes at night & turns icy New snow falls & becomes heavy & slides Slope between 30and 45
Rockfalls Rocks loosened by physical weathering processes
Freezing Thawing Plant growth
Mass Movements & Humans Construction of buildings, roads, etc can
make slopes unstable Trenches
Divert water around slope Covering steep slopes w/steel nets Constructing fences along highways Retaining walls to support weakened slopes Education about building on slopes
List possible locations of mass movements in our area & escape routes.
Which regions of the world are mudslides more common?