Atrani, Amalfi Coast, Italy

Atrani After the Mudflow

Photo Credit: Flickr

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?