Landslides and Mass Movements

The video explains the 1980 Mount St. Helens eruption and the role of gravity in erosion. It covers mass movements like landslides, rock falls, mudflows, and lahars, highlighting their causes and effects. The concept of creep as a slow mass movement is also discussed. The video concludes with resources for further learning.

What natural event triggered the landslide at Mount St. Helens in 1980?

• A tornado

• A flood

• An earthquake

• A hurricane

What is the term used to describe the downward movement of rocks and soil due to gravity?

• Mass movement

• Weathering

• Sedimentation

• Erosion

What is the steepest angle at which loose material will not slide downward called?

• Inclination angle

• Slope angle

• Angle of repose

• Critical angle

Which type of mass movement involves the sudden and rapid movement of a large amount of material downward?

• Landslide

• Slump

• Creep

• Rock fall

What natural factors can increase the chances of a landslide?

• Heavy rains and deforestation

• Low humidity and clear skies

• Snowfall and high winds

• Drought and high temperatures

What is a rapid movement of a large mass of mud called?

• Lahar

• Rock fall

• Mudflow

• Slump

What can cause a lahar?

• Heavy rains on volcanic ash

• Snowfall

• Deforestation

• Earthquakes

What happens when heavy rain mixes with soil and rock on a slope?

• A slump

• A mudflow

• A landslide

• A rock fall

What is the term for the very slow movement of soil downhill?

• Landslide

• Mudflow

• Creep

• Slump

What evidence might indicate that soil creep is occurring?

• Large boulders at the base of a slope

• Straight tree trunks

• Bent tree trunks

• Rapid mudflows