Mass Movement

UNIT 5

STANDARDS:

STATE OBJECTIVES: NCES 2.1.1, 2.1.3, 2.1.4

LESSON 4

Lesson Objectives

In this lesson, you will learn about:What is mass movementThe factors that affect mass movementHow mass movement affects peopleThe relationship between gravity and mass movement

What is Mass Movement Definition

Video (4:44 min)

The down slope movement of loose sediments & weathered rock as a result of gravity.

As weathering breaks down the rocks into smaller pieces, gravity will cause the broken pieces to move down hill.

All mass movements occur on a slope.

Variables to Mass Movement Material’s Weight

Resistance to Sliding

Trigger

Mass of the material and the force pulling on it by gravity

The surface texture is responsible for resistance to sliding

What triggers the initial movement of the material

Let’s not forget Water Effects of water on mass

movement

Video (2:28 min)

Too little water prevents sediment holding together

Too much causes particles to slip

Saturation is too much water Acts as a lubricant Can also cause streams or

flows of water thus moving the material

Types of Mass Movement

Mass movements are classified as:

CreepsFlowsSlides, Slumps, AvalanchesFalls

Creep Definition The steady downhill flow of

loose materials Flow is a few centimeters per

year (inch/yr) Only noticeable over years Can cause tilting of utility

poles, fences, damage to walls

Solifluction Definition The slow downhill

movement of loose water-logged materials that occurs in regions of permafrost.

The material is mudlike Melted iced on top cannot

drain because of the frozen permafrost below

Flows Definition

Video 1 Video 2

When earth materials flow as if they are a liquid

Mudflows are swift moving mixtures of mud and water

Mudflows common in volcanic regions

Mudflows may result in times of severe rain and flooding

Slides: Get out of the Way Landslide

Slump

Avalanche

When a section of earth breaks free of the bedrock and moves rapidly downhill

When sections of the soil become supersaturated and flows down behind the advancing flow of material

Generally in mountainous regions. When ice forms over snow and then breaks free causing a downhill movement of snow and ice

Falls…Help I’ve fallen and… What classifies as a fall Rock falls commonly

occur in high elevations Rocks are loosened by

weathering, freezing, and thawing, as well as plant growth

The rock breaks off and falls…down

Human Impact of Mass Movement People living in areas of potential landslides or

avalanches are at the greatest risk Precautions can be taken using early warning

systems People should be aware of their surroundings and

the amount of rainfall in these areas People living in the valleys or downhill of these

areas are the the greatest risk

Lesson Review Identify and describe one type of rapid mass movement

and one type of slow mass movement Describe the underlying force behind all mass movements How does water affect the process of mass movement Explain how one type of human activity can increase the

risk of mass movement Suggest a solution to the problem you just explained.