Geology ( Mass movement and Surface water)

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