What are Mass Movements?

Now that we have covered the types, causes, and results of weathering, we can move on to the second leveling force:  Erosion.  You will remember that EROSION IS THE REMOVAL AND TRANSPORTATION OF WEATHERED ROCK BY A NATURAL AGENT.  Today you will read about the most dramatic examples of erosion called mass movements.

Mass Movements

A MASS MOVEMENT IS THE MOVEMENT O LOOSE EARTH MATERIAL (ROCK AND SOIL) DOWN STEEP SLOPES.  THE AGENT OF EROSION THAT CAUSES MASS MOVEMENTS IS GRAVITY.  Because this is such a broad definition there are several different types of mass movements we need to be familiar with.   

Creep

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CREEP IS A VERY SLOW, ALMOST IMPERCEPTIBLE DOWNHILL MOVEMENT OF SOIL..

 Creeps are not very exciting, they are just soil moving really really slow down a hillside over time.  Usually they happen so slowly that the only way to know they are occurring is by finding evidence on the landscape.  

TILTED TELEPHONE POLES, AND FENCE POSTS ARE GOOD INDICATORS THAT A HILLSIDE IS CREEPING. 

 

Slumps

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SLUMPS OCCUR WHEN SMALL BLOCKS OF LAND TILT AND MOVE DOWNHILL..  These are common on cliffs, steep hills, and road cuts.  

THEY ARE EASY TO RECOGNIZE BECAUSE THEY LOOK LIKE A HILLSIDE THAT LOOKS LIKE IT HAS BIG STEPS IN IT.

 

Landslide

LANDSLIDES ARE THE VERY SUDDEN, VERY RAPID MOVEMENT OF BEDROCK OR LOOSE ROCK DOWN A STEEP SLOPE.

Landslides can be more specifically identified as rockslides, or mudslides.  The difference is that a mudslide is the sudden movement of wet soil called mud.  They happen in mountainous areas after long periods of heavy rain.    

A result of landslides is TALUS, THE PILE OF ROCKS AND BOULDERS AT THE BASE OF A HILL. 

 

Avalanche

AVALANCHES ARE THE MOVEMENT OF SNOW, ICE, SOIL, ROCK, TREES, ALL MIXED UP IN ONE GIANT WAVE MOVING DOWN A MOUNTAINSIDE.

They are extremely dangerous, because they are very fast, and unpredictable.  Often times, mountain rangers will trigger avalanches on purpose so that they can reduce the risk of them happening in the future.