Lecture 19- Mass Wasting Flashcards
What is mass wasting?
Failure and downslope movement of rock or unconsolidated materials due to gravity
What are unconsolidated materials
Material derived from disintegration and erosion of rocks on the land’s surface, including clay, silt, sand and gravel
Is Mass wasting same as landslide
Yes, specific type of mass wasting characterized by a rapid slope failure
What is erosion
Geological process in which materials are worn away and potentially transported naturally by wind or water
Erosion is driven by?
Gravity
Erosion of hills/mountains results in?
Sloped surfaces of varying stability
A sloped surface’s stability will depend on:
Angle of the slope
Strength of underlying materials due
To determine whether or not a rock will move down a surface, you must consider interaction between rock and sloped surface. IF rock has already broken from the surface, the interaction is ___? Versus if rock is still part of surface, interaction is __? STRENGTH of this interaction is referred to as ___?
Weak
Strong
SHEAR STRENGTH
Force of gravity pulls everything towards?
Earth’s centre (straight down)
Shear force causes rock to move?
Downhill
The steeper the slope, the greater the:
Shear force
Shear force: force component parallel to slope
Normal force: force component perpendicular to slope.
Steeper the slope, the greater the
SHEAR FORCE
What is shear strength?
Fixed at a specific value, shear strength is the strength of interaction between rock and surface
(Kinda like friction)
As slope gets steeper, shear force increases, so
shear force > shear strength
Younger mountains tend to be steeper because?
They have not eroded as much as older mountain chains
Older mountains are less steep because?
They have experienced hundreds of millions of years of erosion. They can still experience mass wasting thought
As rock strength increases, so does?
SHEAR STRENGTH.
(It is the strength of interaction between rock and surface)
Rocks made of crystallized molten materials are very strong. They include:
Granite
Basalt
Gneiss
What is a crystal:
solid whose atoms are arranged in a
“highly ordered” repeating pattern/solid with a “highly
ordered” microscopic arrangement of atoms.
What are potentially strong sedimentary rocks?
Dolostone (made primarily of mineral Dolomite)
Limestone (made of calcite)
Calcite= CaCO3
What are moderately strong sedimentary rocks?
Conglomerate (clastic sedimentary rock largely made up of gravel-sized chunks cemented together.
CLASTIC rocks: rocks composed of fragments
derived from preexisting rocks that are bound
together.
What is a WEAK sedimentary rock
Mudstone (soft and brittle), made of fine particles of clay or mud deposited in aquatic environments
Sandstone can be moderately strong or weak. Sandstone made up of sand grains are held together by a mineral cement. Cement can include:
Silica, calcite, iron oxides…
What is degree of cementation
How well sand grains held together
