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Roger Weller, geology instructor

by Alex Jirousek
Physical Geology
Fall 2009

A Brief History of Landslides


              Landslides have been occurring naturally for millions of years, slowly carving the earth.  The presence of man has only contributed to the frequency of landslides.  Humans have built homes on steep slopes, and humans have cut into already steep slopes to build roads and install utility lines.  The picture below shows a road that has surely contributed to the landslide that occurred on a severe slope.

Dangerous landslides

            Even before humans, landslides kept a natural balance as the surface of the planet constantly changed.  Volcanoes and tectonic plate activity caused the mountain ranges to spring up in the first place.  Then, over time, through wind, rain, and other forms of natural erosion(including landslides) the mountains were steadily reduced creating a constant geological cycle.

            One of the reasons landslides have been so hazardous is that they have occurred in every state in the U.S.  More than 25 people have died every year due to landslides.  An estimated $1-2 billion dollars in damage is done every year in the U.S. alone.  The picture below shows someone’s pick-up truck in someone else’s garage along with several tons of mud.  The two vehicles that were supposed to be in the garage are completely buried.

            Some areas of the U.S. have been considered hotspots for landslides.  This is largely due to the frequency of other natural disasters like floods, earthquakes, even wildfires.  Large mountain ranges and along large rivers are also places where landslides have occurred frequently.  The map below clearly illustrates high-risk areas for landslides.  The Appalachian and Rocky Mountains, the Mississippi River, and the west coast of the U.S. are all places where landslides have been common.

            The U.S. is not alone though, landslides have occurred all over the world.  Some of the areas landslides have commonly occurred have been densely populated, such as southeast Asia.  The map below shows that the north and south poles are safest places on earth, however uninhabitable they might be.  The black dots show where landslides occurred between 2003 and 2006. 


Map of landslide susceptibility and recorded landslides.

            After millions of years, and an increasing human impact there is no sign of decline for landslides now.  Before building a house on the hillsides of the California coast, consider the lay of the land and its’ ever-changing surface.  After all, what goes up must come down.