Flashcards in Lecture 13 Deck (23)
Is shear stress the driving or resisting force?
What is shear stress?
The downslope force from gravity acting on mass slope. Driving force
Is shear strength the driving or resisting force?
What is shear strength?
Retaining force due to particle arrangement. Resisting force
What forced are at work in mass wasting?
Driving force (shear stress)
Resisting force (shear strength)
Force of gravity
What is pour water pressure?
The strength of water in a matrix. When it is negative there is suction, when it is positive there is buoyancy.
What is the factor of safety?
When does a slope because unstable?
When the factor of safety is less than 1
What three factors control mass wasting?
Strength of slope materials
Slope over steepening
What can act as a triggering mechanism for mass wasting?
Is mass wasting natural?
Yes when a slope is trying to come back to equilibrium
What are the five roles of water in mass wasting?
Lubrication (reduces friction)
Erosive agent (direct removal)
Added weight (1000x more dense than air)
Positive pour water pressure (buoyancy)
Dissolves cohesive agents (clays minerals)
What are the four main types of mass wasting?
Flows and slides
What distinguishes the four main types of mass wasting?
Define a soil creep.
Slow gradual down slope movement of surface material, low water content.
Slow Downslope movement of saturated sediment lobes.
What differs gelifluction and solifluction?
Gelifluction occurs when ice is present
Define a slump.
Quick release of sediment in a rotational motion
Define a flow.
Movement of materials with high moisture very quickly
Define falls and slides.
Rapid movement of material either through air (fall)or down a slope (slide)
What is the number one most fatal natural hazard?
Do colder or warmer climates promote faster weathering?