Bill Schulz, USGS Research Geologist, takes photographs of Puerto Rican hillsides from a U.S. Army helicopter to document landslides caused by Hurricane Maria.
What is the difference between a landslide advisory, a landslide watch, and a landslide warning?
An advisory is a general statement about the potential of landslide activity in a given region relative to developing rainfall predictions. An advisory may include general statements about rainfall conditions that can lead to debris-flow activity, and list precautions to be taken in the event of heavy rainfall.
A watch means that landslide-activity will be possible, but is not imminent. People in, or planning to travel through, a watch area should know landslide preparedness and stay informed about developing weather patterns.
Warnings indicate that landslide activity is presently occurring and extreme caution should be taken.
Watches and warnings may be issued for discrete areas, and include advice about contacting an area's local emergency centers. Watches and warnings for rainfall-induced debris flows are weather dependent and will closely track National Weather Service watches and warnings for flash flooding.
Learn more:
Related Content
What is a landslide and what causes one?
A landslide is defined as the movement of a mass of rock, debris, or earth down a slope. Landslides are a type of "mass wasting," which denotes any down-slope movement of soil and rock under the direct influence of gravity. The term "landslide" encompasses five modes of slope movement: falls, topples, slides, spreads, and flows. These are further subdivided by the type of geologic material...
Why study landslides?
Landslides are a serious geologic hazard common to almost every State in the United States. As people move into new areas of hilly or mountainous terrain, it is important to understand the nature of their potential exposure to landslide hazards, and how cities, towns, and counties can plan for land-use, engineering of new construction and infrastructure which will reduce the costs of living with...
Do human activities cause landslides?
Yes, in some cases human activities can be a contributing factor in causing landslides. Many human-caused landslides can be avoided or mitigated. They are commonly a result of building roads and structures without adequate grading of slopes, poorly planned alteration of drainage patterns, and disturbing old landslides. Detailed on-site investigation is required to determine the importance of human...
How many deaths result from landslides each year?
An average of 25-50 people are killed by landslides each year in the United States. The worldwide death toll per year due to landslides is in the thousands. Most landslide fatalities are from rock falls, debris flows, or volcanic debris flows (called lahars). Twenty-three people were killed, at least 167 injured, and more than 400 homes were damaged by a series of debris flows that impacted the...
What is the difference between a landslide advisory, a landslide watch, and a landslide warning?
An advisory is a general statement about the potential of landslide activity in a given region relative to developing rainfall predictions. An advisory may include general statements about rainfall conditions that can lead to debris-flow activity, and list precautions to be taken in the event of heavy rainfall. A watch means that landslide-activity will be possible, but is not imminent. People in...
What was the largest landslide in the United States? In the world?
The largest subaerial (on land) landslide in Earth's recorded history was connected with the 1980 eruption of Mount St. Helens volcano in Washington state, USA. That landslide had a volume of 2.8 cubic kilometers (0.67 cubic miles) of material and the landslide traveled about 22.5 kilometers (14 miles) down the North Fork Toutle River. Average landside depth was 46 meters (150 feet) with a maximum...
Can major landslides and debris flows happen in all areas of the U.S.?
Landslides can and do occur in every state and territory of the U.S.; however, the type, severity, and frequency of landslide activity varies from place to place, depending on the terrain, geology, and climate. Major storms have caused major or widespread landslides in Washington state, Oregon, California, Colorado, Idaho, Hawaii, Virginia, Ohio, Pennsylvania, Tennessee, North Carolina, Puerto...
Under what circumstances do U.S. Geological Survey landslide personnel conduct field work in landslide-prone areas?
USGS landslide researchers have ongoing field projects in several areas of the United States, including parts of the Pacific coastal ranges, Rocky Mountains, and the Appalachians. USGS scientists also respond to major landslide events, including some that result in federally-declared disasters. In some cases, USGS scientists respond to landslides in foreign countries that request assistance...
How do landslides cause tsunamis?
Tsunamis are large, potentially deadly and destructive sea waves, most of which are formed as a result of submarine earthquakes. They can also result from the eruption or collapse of island or coastal volcanoes and from giant landslides on marine margins. These landslides, in turn, are often triggered by earthquakes. Tsunamis can be generated on impact as a rapidly moving landslide mass enters the...
What should I know about wildfires and debris flows?
Wildland fires are inevitable in the western United States. Expansion of human development into forested areas has created a situation where wildfires can adversely affect lives and property, as can the flooding and landslides that occur in the aftermath of the fires. There is a need to develop tools and methods to identify and quantify the potential hazards posed by landslides produced from...
Documenting landslides in Puerto Rico caused by Hurricane Maria.
Bill Schulz, USGS Research Geologist, takes photographs of Puerto Rican hillsides from a U.S. Army helicopter to document landslides caused by Hurricane Maria.
New Zealand Landslides
Photograph showing landslides covering State Route 1 near Ohau Point. The route was impacted my several landslides and is the main north-south highway on the eastern part of the South Island of New Zealand.
Photograph showing landslides covering State Route 1 near Ohau Point. The route was impacted my several landslides and is the main north-south highway on the eastern part of the South Island of New Zealand.
2014 Landslide in Washington State
Photograph from aerial survey showing the upper parts of the landslide that occurred in northwest Washington on March 22, 2014.
Photograph from aerial survey showing the upper parts of the landslide that occurred in northwest Washington on March 22, 2014.
2014 Landslide in Washington State
Photograph from an aerial survey showing the extent and impacts from the landslide in northwest Washington that occurred on March 22, 2014. The survey was conducted by the Washington State Department of Transportation, Washington State Department of Natural Resources, USGS, and King County Sheriff's Office.
Photograph from an aerial survey showing the extent and impacts from the landslide in northwest Washington that occurred on March 22, 2014. The survey was conducted by the Washington State Department of Transportation, Washington State Department of Natural Resources, USGS, and King County Sheriff's Office.
Volcano Web Shorts 2: Debris Flows
Debris flows are hazardous flows of rock, sediment and water that surge down mountain slopes and into adjacent valleys. Hydrologist Richard Iverson describes the nature of debris-flow research and explains how debris flow experiments are conducted at the USGS Debris Flow Flume, west of Eugene, Oregon.
Debris flows are hazardous flows of rock, sediment and water that surge down mountain slopes and into adjacent valleys. Hydrologist Richard Iverson describes the nature of debris-flow research and explains how debris flow experiments are conducted at the USGS Debris Flow Flume, west of Eugene, Oregon.
Related Content
- FAQ
What is a landslide and what causes one?
A landslide is defined as the movement of a mass of rock, debris, or earth down a slope. Landslides are a type of "mass wasting," which denotes any down-slope movement of soil and rock under the direct influence of gravity. The term "landslide" encompasses five modes of slope movement: falls, topples, slides, spreads, and flows. These are further subdivided by the type of geologic material...
Why study landslides?
Landslides are a serious geologic hazard common to almost every State in the United States. As people move into new areas of hilly or mountainous terrain, it is important to understand the nature of their potential exposure to landslide hazards, and how cities, towns, and counties can plan for land-use, engineering of new construction and infrastructure which will reduce the costs of living with...
Do human activities cause landslides?
Yes, in some cases human activities can be a contributing factor in causing landslides. Many human-caused landslides can be avoided or mitigated. They are commonly a result of building roads and structures without adequate grading of slopes, poorly planned alteration of drainage patterns, and disturbing old landslides. Detailed on-site investigation is required to determine the importance of human...
How many deaths result from landslides each year?
An average of 25-50 people are killed by landslides each year in the United States. The worldwide death toll per year due to landslides is in the thousands. Most landslide fatalities are from rock falls, debris flows, or volcanic debris flows (called lahars). Twenty-three people were killed, at least 167 injured, and more than 400 homes were damaged by a series of debris flows that impacted the...
What is the difference between a landslide advisory, a landslide watch, and a landslide warning?
An advisory is a general statement about the potential of landslide activity in a given region relative to developing rainfall predictions. An advisory may include general statements about rainfall conditions that can lead to debris-flow activity, and list precautions to be taken in the event of heavy rainfall. A watch means that landslide-activity will be possible, but is not imminent. People in...
What was the largest landslide in the United States? In the world?
The largest subaerial (on land) landslide in Earth's recorded history was connected with the 1980 eruption of Mount St. Helens volcano in Washington state, USA. That landslide had a volume of 2.8 cubic kilometers (0.67 cubic miles) of material and the landslide traveled about 22.5 kilometers (14 miles) down the North Fork Toutle River. Average landside depth was 46 meters (150 feet) with a maximum...
Can major landslides and debris flows happen in all areas of the U.S.?
Landslides can and do occur in every state and territory of the U.S.; however, the type, severity, and frequency of landslide activity varies from place to place, depending on the terrain, geology, and climate. Major storms have caused major or widespread landslides in Washington state, Oregon, California, Colorado, Idaho, Hawaii, Virginia, Ohio, Pennsylvania, Tennessee, North Carolina, Puerto...
Under what circumstances do U.S. Geological Survey landslide personnel conduct field work in landslide-prone areas?
USGS landslide researchers have ongoing field projects in several areas of the United States, including parts of the Pacific coastal ranges, Rocky Mountains, and the Appalachians. USGS scientists also respond to major landslide events, including some that result in federally-declared disasters. In some cases, USGS scientists respond to landslides in foreign countries that request assistance...
How do landslides cause tsunamis?
Tsunamis are large, potentially deadly and destructive sea waves, most of which are formed as a result of submarine earthquakes. They can also result from the eruption or collapse of island or coastal volcanoes and from giant landslides on marine margins. These landslides, in turn, are often triggered by earthquakes. Tsunamis can be generated on impact as a rapidly moving landslide mass enters the...
What should I know about wildfires and debris flows?
Wildland fires are inevitable in the western United States. Expansion of human development into forested areas has created a situation where wildfires can adversely affect lives and property, as can the flooding and landslides that occur in the aftermath of the fires. There is a need to develop tools and methods to identify and quantify the potential hazards posed by landslides produced from...
- Multimedia
Documenting landslides in Puerto Rico caused by Hurricane Maria.
Bill Schulz, USGS Research Geologist, takes photographs of Puerto Rican hillsides from a U.S. Army helicopter to document landslides caused by Hurricane Maria.
Bill Schulz, USGS Research Geologist, takes photographs of Puerto Rican hillsides from a U.S. Army helicopter to document landslides caused by Hurricane Maria.
New Zealand LandslidesPhotograph showing landslides covering State Route 1 near Ohau Point. The route was impacted my several landslides and is the main north-south highway on the eastern part of the South Island of New Zealand.
Photograph showing landslides covering State Route 1 near Ohau Point. The route was impacted my several landslides and is the main north-south highway on the eastern part of the South Island of New Zealand.
2014 Landslide in Washington StatePhotograph from aerial survey showing the upper parts of the landslide that occurred in northwest Washington on March 22, 2014.
Photograph from aerial survey showing the upper parts of the landslide that occurred in northwest Washington on March 22, 2014.
2014 Landslide in Washington StatePhotograph from an aerial survey showing the extent and impacts from the landslide in northwest Washington that occurred on March 22, 2014. The survey was conducted by the Washington State Department of Transportation, Washington State Department of Natural Resources, USGS, and King County Sheriff's Office.
Photograph from an aerial survey showing the extent and impacts from the landslide in northwest Washington that occurred on March 22, 2014. The survey was conducted by the Washington State Department of Transportation, Washington State Department of Natural Resources, USGS, and King County Sheriff's Office.
Volcano Web Shorts 2: Debris FlowsDebris flows are hazardous flows of rock, sediment and water that surge down mountain slopes and into adjacent valleys. Hydrologist Richard Iverson describes the nature of debris-flow research and explains how debris flow experiments are conducted at the USGS Debris Flow Flume, west of Eugene, Oregon.
Debris flows are hazardous flows of rock, sediment and water that surge down mountain slopes and into adjacent valleys. Hydrologist Richard Iverson describes the nature of debris-flow research and explains how debris flow experiments are conducted at the USGS Debris Flow Flume, west of Eugene, Oregon.
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