Friday
February 18, 2011
(Mass Wasting)
The Launch Pad
Friday, 2/18/11
No Launch Pad Today.
Announcements
We will have a test next
Tuesday.
Assignment Currently Open
Date Issued
Date Due
WS – The Rock Cycle
1/19
1/21
WS – Igneous Rocks (Part 1)
1/20
1/21
Lab – Igneous Rocks
1/21
1/21
WS – Igneous Rocks (Part 2)
1/24
1/26
PowerPoint – Common Igneous Rocks
1/24
1/26
WS – Sedimentary Rocks (Part 1)
1/25
1/27
WS – Sedimentary Rocks (Part 2)
1/26
1/28
Lab – Sedimentary Rocks
1/27
1/27
WS – Metamorphic Rocks
1/28
2/2
Lab – Metamorphic Rocks
1/31
1/31
Test 6
2/10
2/10
WS – Weathering
2/11
2/18
WS – Soil
2/15
2/22
Cornell Notes Today!
What is Mass Wasting?
Earth’s surface is never
perfectly flat, but instead
consists of slopes.
Mass wasting is the
down-slope movement of
rock, regolith, and soil
under the direct influence
of gravity (the controlling
force.)
Factors That Trigger Mass Wasting
There are several factors that are
important to the triggering of
mass wasting:
1) Over-steepening of slopes.
•
•
•
Unconsolidated granular
particles assume a stable slope
called the angle of repose.
The stable slope angle is
different for various materials.
Over-steepened slopes are
unstable.
Factors That Trigger Mass Wasting
2. Removal of anchoring vegetation
3. Ground vibrations from earthquakes
4. Saturation of the material with water
destroys particle cohesion. Water adds
weight.
The Effect of Water on Mass Wasting
Types of Mass Wasting Processes
Generally, each type of mass
wasting process is defined by:
1. the material involved
– debris, mud, earth,
or rock
Debris Flow
Types of Mass Wasting
Processes
Generally, each type of mass
wasting process is defined by:
2.
the movement of the
material
 Fall (freefall of pieces)
 Slide (material moves
along a well-defined
surface)
 Flow (material moves
as a viscous fluid)
 Slump (rapid
movement along a
curved surface)
A slump with an
earthflow at the base
Figure 4.28 A
Types of Mass Wasting Processes
Generally, each type of mass wasting process is
defined by:
3.
The rate of the movement
 Fast
 Slow
Forms of Mass Wasting
Rockslide (rapid, blocks of bedrock move down a slope)
Debris flows composed mostly of volcanic materials are called lahars
Rock Slide
Forms of Mass Wasting
Forms of Mass Wasting
Earthflow is a rapid form
of mass wasting.
Earthflow typically occur
on hillsides in humid
regions where water has
saturated the soil.
Liquefaction is a special
type of earthflow
sometimes associated
with earthquakes.
Forms of Mass Wasting
Creep is a slow
movement of soil and
regolith downhill. It can
cause fences and utility
poles to tilt.
Forms of Mass Wasting
Solifluction is a slow
movement in areas underlain
by permafrost. The upper
(active) soil layer becomes
saturated and slowly flows
over a frozen surface below.