this presentation cover some explanation on mass wasting its types , occurrence, causes its landforms .

1. Geomorphology Presentation
prepared by : 2ND Semester “Group B” students
Topic : MASSWASTING
Contents
• Types
• Occurrence
• Deposits and landforms
• Causes
• Hazard and mitigation

2. Mass wasting .
At the end of this chapter, students should be able to:
• Explain what mass wasting is and why it occurs on a slope
• Explain the basic triggers of mass-wasting events and how they occur
• Identify types of mass wasting
• Identify risk factors for mass-wasting events
 Mass wasting, also known as mass movement, is a general term for the
movement of rock or soil down slopes under the force of gravity. It differs
from other processes of erosion in that the debris transported by mass
wasting is not entrained in a moving medium, such as water, wind, or ice.

4. Types Of Mass wasting
• Types of mass wasting include creep, solifluction , rockfalls, debris flows,
and landslides, each with its own characteristic features, and taking place
over timescales from seconds to hundreds of years. Mass wasting occurs
on both terrestrial and submarine slopes.
• Creep , Soil creep is a slow and long term mass movement. The
combination of small movements of soil or rock in different directions over
time is directed by gravity gradually downslope. The steeper the slope, the
faster the creep. The creep makes trees and shrubs curve to maintain their
perpendicularity, and they can trigger landslides if they lose their root
footing. The surface soil can migrate under the influence of cycles of
freezing and thawing, or hot and cold temperatures, inching its way
towards the bottom of the slope forming terracettes. Landslides are often
preceded by soil creep accompanied with soil sloughing — loose soil that
falls and accumulates at the base of the steepest creep sections.

6. Solifluction
• Solifluction is a form of creep characteristics of arctic or alpine
climates. It takes place in soil saturated with moisture that thaws
during the summer months to creep downhill. It takes place on
moderate slopes, relatively free of vegetation, that are underlain by
permafrost and receive a constant supply of new debris by
weathering. Solifluction affects the entire slope rather than being
confined to channels and can produce terrace-like landforms or stone
rivers.

8. Rockfall
• A rockfall is a type of fast-moving landslide that happens when
rock or earth falls, bounces, or rolls from a cliff or down a very
steep slope. Rockfalls start from high outcrops of hard, erosion-
resistant rock that become unstable for a variety of reasons.

9. Mudflows and Debris Flows
• when a mass of sediment becomes completely saturated with water,
the mass loses strength, to the extent that the grains are pushed apart,
and it will flow, even on a gentle slope. This can happen during rapid
spring snowmelt or heavy rains, and is also relatively common during
volcanic eruptions because of the rapid melting of snow and ice. (A
mudflow or debris flow on a volcano or during a volcanic eruption is
a lahar.) If the material involved is primarily sand-sized or smaller, it
is known as a mudflow, If the material involved is gravel sized or
larger, it is known as a debris flow. Because it takes more gravitational
energy to move larger particles, a debris flow typically forms in an
area with steeper slopes and more water than does a mudflow.

10. Debris flow
Mudflow

11. Debris flow Mud flow

12. Landslide
• A landslide, also called a landslip,is a relatively rapid movement of a
large mass of earth and rocks down a hill or a mountainside.
Landslides can be further classified by the importance of water in the
mass wasting process. In a narrow sense, landslides are rapid
movement of large amounts of relatively dry debris down moderate
to steep slopes. With increasing water content, the mass wasting
takes the form of debris avalanches, then earthflows, then mudflows.
Further increase in water content produces a sheetflood, which is a
form of sheet erosion rather than mass wasting.

14. Occurrences
• On Earth, mass wasting occurs on both terrestrial and submarine slopes.
Submarine mass wasting is particularly common along glaciated coastlines
where glaciers are retreating and great quantities of sediments are being
released. Submarine slides can transport huge volumes of sediments for
hundreds of kilometers in a few hours.

15. Occurrences
• On other planets. Mass wasting is a common phenomenon
throughout the Solar System, occurring where volatile materials are
lost from a regolith. Such mass wasting has been observed on Mars,
Io, Triton, and possibly Europa and Ganymede. Mass wasting also
occurs in the equatorial regions of Mars, where stopes of soft sulfate-
rich sediments are steepened by wind erosion. Mass wasting on
Venus is associated with the rugged terrain of tesserae.shows
extensive mass wasting of its volcanic mountains.

16. Deposits and landforms
• Mass wasting affects geomorphology, most often in subtle, small-scale ways, but occasionally
more spectacularly.
• Soil creep is rarely apparent but can produce such subtle effects as curved forest growth and
tilted fences and telephone poles. It occasionally produces low scarps and shallow depressions.
• Solifluction produced lobed or sheetlike deposits, with fairly definite edges, in which clasts (rock
fragments) are oriented perpendicular to the contours of the deposit.
• Rockfall can produce talus slopes at the feet of cliffs. A more dramatic manifestation of rockfall is
rock glaciers, which form from rockfall from cliffs over steepened by glaciers.
• Landslides can produce scarps and step-like small terraces . Landslide deposits are poorly sorted.
Those rich in clay may show stretched clay lumps (a phenomenon called boudinage) and zones of
concentrated shear.
• Debris flow deposits take the form of long, narrow tracks of very poorly sorted material. These
may have natural levees at the sides of the tracks, and sometimes consist of lenses of rock
fragments alternating with lenses of fine-grained earthy material. Debris flows often form much
of the upper slopes of alluvial fans.

17. Causes
• Triggers for mass wasting can be divided into passive and activating (initiating)
causes.
Passive causes include
• Rock and soil lithology. Unconsolidated or weak debris are more susceptible to
mass wasting, as are materials that lose cohesion when wetted.
• Stratigraphy, such as thinly bedded rock or alternating beds of weak and strong
or impermeable or permiable rock lithologies.
• Faults or other geologic structures that weaken the rock.
• Topography, such as steep slopes or cliffs.
• Climate, with large temperature swings, frequent freezing and thawing, or
abundant rainfall
• Lack of vegetation

18. Activating causes include
• Undercutting of the slope by excavation or erosion
• Increased overburden from structures
• Increased soil moisture
• Earthquakes
Methods of mitigation of mass wasting hazards include:
• Afforestation
• Construction of fences, walls, or ditches to contain rockfall
• Construction of catchment dams to contain debris flows
• Improved drainage of source areas
• Slope stabilization

19. Any Question?

20. Reference
• Introduction to physical geology 15th edition
• Internet
• Physical geology 13th edition
THANK YOU