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What is mass movement?
the downward movement of rock and soil debris down a slope under the influence of gravity
Is mass movement always a fast process?
no, it can occur slowly over time, like in soul creep, or rapidly as in landslide or rock fall. Depends on the conditions involved
How does mass movement relate to landscape development over time?
it plays a significant role in shaping landscapes over time. Denudation, mountain landscapes, and coastal landscapes, and elevation limits.
Mass mvement relates to denudation?
gradually wears away the landscapes built by plate tectonics
Mass movement relates to mountain landscapes?
responsible for the morphology of most mountain ranges
Mass movement relates to Coastal landscapes?
the development of coastal erosion and depositional landform
Mass movement relates to elevation limits?
limit the maximum elevation of orogens
How do mass movement fluvial erosion and transport affect landscape development over time?
it reshapes the earth’s surface, creating new landforms and altering the topography of rivers, streams, and forests.
What characteristics are used to classify different types of mass movement?
The speed of movement, the type of material involved, the character of the movement, the water content
What factors or processes can increase the probability of mass movement occurring?
steep slopes, high water saturation in soil or rock, lack of vegetation, seismic activity like earthquakes, weathering that weakens the rock material, human activities like deforestation or construction on slopes, heavy rainfall, rapid snowmelt, weak geological formations like fault lines or bedding planes
What is meant by angle of repose?
The angle that the plane of contact between two bodies makes with the horizontal when the upper body is just on the point of sliding
How does water affect the angle of repose of sediment?
Decreases the angle of repose of sediment by filling the spaces between grains, reducing friction between them, and essentially making the sediment behave more like a fluid when saturated, leading to a lower stable slope angle.
How does the movement occur in the case of heave-facilitated creep?
The material moves downslope due to upward heaves and downward resettling.
high areas near slopes get what?
get worn down
low areas near slopes get what?
get filled in
type of motion: fall
rockfall, debris fall
types of motion: slide
debris, rock, and block slide
Translational slide
the material moves along a flare surface
rotational slide
aka slumps, material moves along a surface that is concave up
type of motion: Flow
debris, mud, and earth flow
types of motions: avalanches
most rapid form of mass movement
types of motions: lahars
mudflow or debris flows that originate on volcanoes
How does water get into the atmosphere and become rain or snow?
Enters the atmosphere through evaporation, turning liquid water into water vapor which rises into the air; as it reaches cooler temperatures higher up, this vapor condenses into clouds, and when the clouds become saturated, water falls back to earth as precipitation like rain or snow.
Where does water from rain and snow go after it hits the surface?
Runoff: water that flows over the surface of the land into rivers, lakes, or the ocean
Infiltration: soak into the ground
What are drainage divides?
Divides areas where water flows into different oceans/seas/bays
How do they relate to continental divides?
A large-scale drainage divides that separates river systems draining into different oceans on a continent
What is the meaning and importance of a stream’s base level?
The lowest point to which running water can flow
What is a graded stream?
A stream that reaches a state of equilibrium where the slope of its channel is perfectly adjusted to carry the amount of sediment supplied to it
What are the different ways in which streams…..
erode bedrock and transport sediment
erode bedrock examples
abrasion, quarrying, and corrosion
abrasion?
grinding by sediment carried in the water
quarrying?
removing large bedrock blocks from the channel bed
corrosion?
flowing water dissolves bedrock
transport sediment examples
suspended load and bed load
suspended load?
fine particles carried within the water column
corrosion?
transport along channel bed, large particles (gravel, boulders)
Why is sediment deposited when a river empties into a body of water……
because the river’s current slows down significantly at the mouth, reducing its ability to carry the sediment particles
Why is sediment deposited when a river empties onto a flat plain…..
The sudden decrease in slope causes the water to slow down significantly, losing the energy needed to carry the sediment particles, which then settle out and accumulate on the plain.
Are sediments deposited by streams usually well-sorted or poorly sorted?
Poorly sorted because the energy of the water flow varies within a stream leading to a mix of different grains.
water flow can be two types
laminar flow and turbulent flow
laminar flow?
Flowing in a nearly straight path and parallel to the stream channel
turbulent flow?
flowing chaotically or erractically in all directions
channel properties affect flow velocity
channel slope and channel shape
channel slope?
steeper gradient means more gravitational energy to drive flow
channel shape?
water flows faster in narrow and deep channels and slower in wide and shallow channels
competence?
the largest particle size a stream can transport
capacity?
a maximum load a stream can transport over a given time
alluvial fans?
Fan-shaped sediment deposits at the base of mountain fronts
natural levees?
Raised areas adjacent to the channel, Form during flood events
bedrock channels?
Channels cut into bedrock, Typically form in headwater region
alluvial channels?
Channels cut into previously deposited stream sediments, Typically associated with floodplains, Changes shape and location
base level?
The lowest level to which a stream can erode its channel
graded stream?
A stream that maintains a minimum flow rate necessary to transport the sediment that is delivered to it
Stream valley deepening
When a channel has a steep gradient, Downcutting leads to a V shape with steep sides
Stream valley widening
A stream approaches the graded condition, Erosion occurs laterally, Produces flood plain
Incised Meanders
Meanders flowing through steep, narrow bedrock valleys, Develop on a floodplain, The height difference between stream and its base level increases relatively quickly
Stream drainage patterns
A network of stream valleys creates a drainage pattern, Patterns develop depending on regional terrain properties
