DRR Q4 Lesson 1: Landslides

Mass Wasting

It is the downward movement of rocks, soil and caused by gravity

Gravity causes materials to move downslope

Resisting forces help maintain slope stability (materials' strength and cohesiveness)

Steeper Slopes

Are more likely to experience mass wasting

The root system of plants bind the soil and regolith together, minimizing the downslope movement

Large amounts of water from melting snow and heavy rainfall greatly increase slope failure

RAPID MASS MOVEMENT

SLOW MASS MOVEMENT

2 CLASSIFICATIONS OF MASS WASTING

RAPID MASS MOVEMENT

- Sudden or rapid movement of materials downslope

SLOW MASS MOVEMENT

Usually detectable only be the effects of movement (e.g tilted trees)

ROCK FALL

The boulders fall and break off, producing coarse debris at the base of the slope

SLIDE

Includes movement of materials above one or more surface of failure.

Rock or soil material or a combination of rock and soil may break apart or remain intact during movement.

SLUMPS

BLOCK SLIDE

2 TYPES OF SLIDE

SLUMPS

- Is mostly cause by soil erosion along the base of the slope that removes the support of overlying materials

BLOCK SLIDE

- Occurs when rocks move downslope along more planar surface.

CREEP

Is the extremely slow downhill movement of soil and uppermost bedrock zones.

The slow movement of material downslope happens when clay-rich soil gets wet and expands and lifting the materials slightly.

FLOWS

Are mass movements in which materials move as or behave like a viscous fluid or display plastic movement.

Materials like: sand, clay, snow and ice.

MUDFLOW

DEBRIS FLOW

SOLIFLUCTION

FERMAFROST

4 TYPES OF FLOW

MUDFLOW

Quickly moving downhill flow of soil and rock fragments containing a large amount of water

DEBRIS FLOW

A downslope movement of mud mixed with larger rock fragments.

SOLIFLUCTION

Slow, downslope flow of water-saturated materials common to permafrost areas.

PERMAFROST

permanently frozen layer of soil beneath the surface of the ground

RAINFALL-INDUCED LANDSLIDE

Is described as the downslope movement of materials that can either be a cohesive mass, soil, rock and regolith

loose unconsolidated rock and dust that sits atop a layer of bedrocK

During heavy rains, water content in soil increased, this reduces the cohesion among soil particles

REGOLITH

loose unconsolidated rock and dust that sits atop a layer of bedrock

Porosity

Water is found in the pores between particles of rock & other material. The more pores there are, the more water can be held.