Causing $1-2 billion in damages and more than 25 deaths per year, landslides are
a major geologic hazard, caused by earthquakes and floods. Although, landslides
are generally not as exciting or costly as earthquakes, major floods, tropical
storms, and other natural disasters, they occur in more expanded places and may
cause more property damage than any other geologic hazards. A wide variety of
ground movements, such as rock falls, slope failure, and shallow debris flows
can classify landslides. When a portion of a hill slope cannot support its own
weight a landslide will occur. When rainfall or some other water source
increases the water content of the slope the weakness is irritated, reducing the
strength of the materials. Although gravity acting upon an increased slope is
the main reason for a landslide, there are other elements that contribute to its
cause. Loud sounds that occur during an earthquake also cause landslides.
Erosion caused by rivers, glaciers, or ocean waves create oversteepened slopes.
Heavy rains and melting snow weaken rock and soil slopes. Furthermore,
vibrations from machinery, traffic, and even thunder may trigger failure of weak
slopes. Excess water can run through slope material and can cause a debris flow
or mud flow. The rock and mud left over after a landslide may pick up anything
in its path, such as trees, houses, and cars, causing bridges and tributaries to
become blocked which causes flooding throughout its path. Even though, the
natural cause of most landslides is unable to be stopped, geologic
investigations, good engineering practices and effective enforcement of land-use
management regulations can cut back landslide danger. Landslides effect every
state in the United States territory. The Appalachian Mountains, the Rocky
Mountains and the Pacific Coastal Ranges and few parts of Alaska and Hawaii have
intense landslide problems. USGS marine scientists have recently identified over
fifteen giant landslides surrounding the Hawaiian Islands. These slides are some
of the largest known on Earth, and most have taken place throughout the past
four million years. The youngest landslide is estimated to have occurred only
one hundred thousand years ago, and there is evidence today that large blocks of
the island are starting to slide, causing enormous earthquakes. Each landslide
that has happened over the bast four million years has ended with huge land loss
and gigantic waves that move rocks and sediments up to 1000ft above sea level.
The geologic hazards are important to learn about because, they don't occur as
frequently as volcanoes or other disasters, they have potential to destroy
lives, property, and natural resources (Giant Landslides). It is possible that
any area made up of brittle and cracked materials lying on a steep slope will be
subject to landslides. Scientists continue to try their best to lower the risk
of landslides everywhere by producing landslide susceptibility maps for areas in
the United States. Areas that are generally accessible to landslide hazards
include: old landslides, bases of slopes, at the base of minor drainage hollows,
at the base or top of an old fill slope or steep cut slope, and developed
hillsides where leach field septic systems are used. However, there are areas
that are safe from landslide activity: on hard bedrock that has not moved in the
past, on flat land away from rapid changes in slope angle, and at the top or
along the nose of ridges, set back from the tops of slopes. In order to be
prepared for landslides, pay attention to things that might occur before the
hazard. These characteristics include wetness of ground that has not been wet
before, new cracks or bulges in the ground, sidewalk, or street, cracks in
concrete floors and foundations, leaning telephone poles, uneven fence lines,
rapid increase of water level in creaks, and movement of soil away from
foundations. Incase a landslide does occur, contact local fire, police or public
works department, tell affected neighbors, and be sure to evacuate the area.

Bibliography
"Giant Landslides Around the Hawaiian Islands". http://walrus.wr.usgs.gov/docs/projects/haland.html
maintained by Molly Gowen Groome last modified June 10, 1998, accessed 12/10/98.
This page updated: 16 November 1998 For suggestions and comments please send
e-mail to: nlic@usgs.gov. Page URL: http://landslides.usgs.gov/html_files/nlicsun.html
11/30/1998 The URL of this page is http://landslides.usgs.gov/html_files/nlic/new1ft.shtml
Contact: Webmaster@gldage.cr.usgs.gov Updated: Monday November 16 1998
"Landslides." http://germantown.k12.il.us/html/landslides.html
11/30/98 "Fact