mass wasting/lanslides 1 Flashcards
what is mass wasting?
aka. slope failure
failure and downslope movement of rock or unconsolidated materials due to gravity.
what is unconsolidated materials?
Material derived from the disintegration and erosion of rocks on the land’s surface, including clay, silt, sand and gravel.
is mass wasting same as landslide?
For some yes!
For others LANDSLIDE is a 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.
what does a sloped surface’s stability will depend on?
✓ angle of the slope
✓ strength of the underlying materials
what are erosion and the break down of hills and mountains driven largely by?
gravity
what does the erosion of hills/mountains will result in?
in SLOPED surfaces of varying stability
Let us assume we are observing a chunk of rock on a SLOPED surface.
What factors will determine whether or not it will move down the surface (first one)?
- interaction between chunk of rock and SLOPED surface:
-If rock has already broken from the surface:
interaction WEAK.
-If rock is still a part of the surface (connected to surface): interaction STRONG.
-Strength of this interaction is referred to as
SHEAR STRENGTH.
Let us assume we are observing a chunk of rock on a SLOPED surface.
What factors will determine whether or not it will move down the surface (second one)?
- Next, must consider force of GRAVITY acting
on chunk of rock.
-Force of GRAVITY pulls everything towards
Earth’s center (straight down).
-However, a fraction of GRAVITATIONAL force
will want to pull the rock down SLOPE.
what is shear force?
a FORCE component parallel to SLOPE
what is a normal force?
a FORCE component perpendicular to SLOPE
what is the relationship between the slope and the shear force?
STEEPER the SLOPE, GREATER the SHEAR
FORCE
both the shear and normal force act on a chuck of rock, however which force can cause it to move downhill?
the shear force
what is the shear strength and the shear force?
SHEAR STRENGTH is strength of INTERACTION between ROCK and SURFACE
what would happen if SLOPE is small (not steep); SHEAR FORCE is small?
In this case, SHEAR FORCE < SHEAR STRENGTH
Chunk of rock does NOT move.
what would happen as SLOPE gets steeper; SHEAR FORCE increases?
In this case, SHEAR FORCE ≈ SHEAR STRENGTH
Chunk of rock MAY or MAY NOT move.
what would happen as SLOPE gets steeper still; SHEAR FORCE continues to
increase?
In this case, SHEAR FORCE > SHEAR STRENGTH
Chunk of rock will likely move.
which younger or older mountains tend to be steeper?
Younger mountains (more recently formed by tectonic collisions) tend to be steeper as they have not ERODED as much as older mountain chains.
Older mountains less steep as have experienced hundreds of millions of years of EROSION.
That being said, they can still experience some
MASS WASTING.
what is the relationship between rock strength and shear strength?
As rock strength increases, so does SHEAR
STRENGTH
what is igneous rock?
rocks formed when molten material/magma or lava cools and
solidifies.
Visually, these rocks appear to have crystals
and are NEVER LAYERED.
IGNEOUS ROCKS are further subdivided into
INTRUSIVE IGNEOUS ROCKS and
EXTRUSIVE IGNEOUS ROCKS
what is sedimentary rock?
rocks formed from sediments, bits of preexisting rocks and pieces of once-living organisms (e.g., mollusks and other invertebrates)
Furthermore, SEDIMENTARY ROCKS:
➢ have layers
➢ feel gritty (i.e., rough texture/feels like
it is coated in sand)
➢ often break easily
what is metamorphic rock?
IGNEOUS or SEDIMENTARY ROCKS that have been transformed by high pressure, high heat, and/or contact with hot magma.
Find such conditions:
➢ deep in the Earth
➢ where tectonic plates meet
Transformation/METAMORPHISM
process does NOT melt rocks, it just turns them into DENSER and more compact rocks
(remember density is mass/volume).
are rocks made of crystallized molten materials (i.e., minerals) are very strong? if so, what does it include?
yes
These include (but are not limited to):
✓ GRANITE (igneous rock)
✓ BASALT (igneous rock)
✓ GNEISS (metamorphic rock)
what is a crystal?
A solid whose atoms are arranged in a
“highly ordered” repeating pattern/solid with a “highly ordered” microscopic arrangement of atoms.
