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Landslide Basics

Landslides occur in all 50 states and territories and they affect lives, property, infrastructure, and the environment.  Understanding when, where, and how landslides occur can help to reduce the risk of living with these natural hazards.  

rocks, dirt, and shrubs on hillside
A small landslide in the 2017 Thomas fire burn area that initiated during atmospheric river events in December 2022 and January 2023.  

 

What is a landslide?

Landslides occur in all 50 states and territories where they affect lives, property, infrastructure, and the environment.  Landslides are the downslope movement of earth materials (rock, debris, and soil) at rates that range from inches per year to tens of miles per hour. Some landslides can move faster than a person can run. Landslides can happen with no notice or can take place over a period of days, weeks, or longer.  
Big Sur landslide on May 20, 2017 showing material across Highway 1.
USGS air photo of the Mud Creek landslide, taken on May 27, 2017. (Public domain.)

 

 

Where do landslides occur?

Landslides occur in every state and U.S. territory including the Appalachian Mountains, the Rocky Mountains, the Pacific Coastal Ranges, and some parts of Alaska and Hawaii. Any area composed of very weak or fractured materials resting on a steep slope can and will likely experience landslides.

 

 

severe damage to home foundation, homes built on landslide
A reactivated landslide destroyed this home that was built on the landslide. Initial, slow landslide movement allowed the occupant to escape. Island County, WA. March 2013

 

Why should I care about landslides?

Landslides kill people and destroy property.

 

 

 

 

 

 

Aeirial view of landslides blocking roads  in Utuado, Puerto Rico
An aerial view of landslide damage after Hurricane Maria in Utuado municipality, Puerto Rico.

Why do landslides occur?

Landslides occur when forces that form them overcome forces resisting their formation. 

 

 

 

 

 

Center map shows landslide locations. Hills slope from sides down to center of figure with descriptive labels and arrows.
The University of Puerto Rico Mayagüez, the Natural Hazards Center at the University of Colorado Boulder, and the USGS Landslide Hazards Program collaborated to create educational materials for residents of Puerto Rico to learn about how to prepare for, mitigate, respond to, and recover from landslides. Pages from “Landslide Guide for Residents of Puerto Rico “ are shown in this figure. 

How do I prepare for a landslide?

If you live on or below a slope, here are some simple steps you can take to identify a landslide hazard and reduce your landslide risk.

 

 

 

 

 

two cracks on a gravel slope in residential yard
Cracks on a gravel road formed during the initial movement of a slow, deep landslide. The cracks can be indicators of local movement in or around the road or in this case, a much larger landslide and damaged many homes. 

What are the signs of landslide development/movement? What do I do if a landslide occurs?

Landslides are dangerous and very difficult to predict. Some landslides may provide clues that they are about to happen; others may happen suddenly without any warning signs.

 

 

home damaged by a landslide
Home in Utuado Municipality damaged by a landslide from Hurricane Maria.

What do I do after a landslide has occurred?

Depending on the severity of the landslide, you may not be able to return home right away. If authorities say it is safe to return to your home, continue to be prepared to leave the area immediately if you observe unusual activity. 

 

 

 

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