Weathering and Mass Movement Flashcards
1
Q
What is Geomorphology?
A
(morph means shape or form) is the science of landforms including origin, evolution, form, and spatial distribution.
2
Q
What is Denudation?
A
Denudation is any process that wears away or rearranges landforms, stripping away landscapes.
3
Q
What are the principals of Denudation?
A
weathering,
mass movement,
erosion,
transportation,
deposition.
4
Q
What’re the agents of Denudation?
A
Moving water,
air,
waves,
ice
5
Q
Define Weathering:
A
Weakening Water and other weathering agents interact with rock, breaking it down into clasts, mineral particles, or dissolving it.
6
Q
Define Erosion:
A
The removal and subsequent transport of (often weakened) materials Weathering is the breakdown (or weakening) of materials, while erosion removes and transports this material elsewhere.
7
Q
What are earths internal and external processes?
A
Endogenic and Exogenic
8
Q
Endogenic processes build________ landscapes (tectonic activity).
A
initial
9
Q
Exogenic processes develop ________ landscapes of low relief, gradual change, and stability.
A
sequential
10
Q
True or False: The internal and external countering processes act on landscapes simultaneously at different rates.
A
True
11
Q
Explain Denudation v.Tectonics:
A
the interaction of endogenic and exogenic processes.
12
Q
What is the key principal of Differential Weathering?
A
not all rock types are created equal, some are more resistant to weathering than others.
13
Q
What type of approach is used to understand the forces affecting a landscape?
A
Systems approach
14
Q
Is a landscape system a closed or open system?
A
Open
15
Q
Why is a landscape system an open system?
A
It has inputs of energy and materials
16
Q
What are the inputs of materials?
A
Water from precipitation, rocks from tectonic activity.
17
Q
What are inputs of energy?
A
Potential Energy is related to elevation. Kinetic energy is related to motion.
18
Q
Solar radiation= _____________
A
heat energy
19
Q
Water movement=___________
A
kinetic energy
20
Q
Atmospheric and other reactions within the crust=
A
Chemical Energy
21
Q
Crustal uplift =___________
A
potential energy
22
Q
Define a Landscape systems:
A
Balance between endogenic processes and exogenic processes.
23
Q
Which processes create initial landscapes?
A
Endogenic processes build “initial” landscapes.
24
Q
Which processes destroy or modify landscapes?
A
Exogenic processes develop “sequential” landscapes.
25
What happens as physical structures fluctuate in an area?
the surface constantly responds in search of equilibrium. Every change produces compensating actions and reactions.
26
True or False: the surface looks the way it does and is altered / shaped due to the balancing act between tectonic uplift and reduction by weathering and erosion, or between the pull of gravity downslope and the stabilization of the slope by vegetation.
True
27
Define a Slope:
Material loosened by weathering is susceptible to erosion and transportation.
28
What needs to happen for material to move downslope?
the forces of erosion must overcome other forces: friction, inertia (the resistance to movement), and the cohesion of particles to one another.
29
True or False: If the angle is steep enough for gravity to overcome frictional forces or if the impact of raindrops or wind dislodges material, then erosion of particles and transport downslope can occur.
True
30
What are the forces at play on a slope?
exogenic processes to weaken the rock and the surface, potential energy due to uplift. Gravity trying to keep the material on the slope (angle is a factor), frictional resistance to counteract gravitational energy.
31
What is a stable slope?
A slope is stable if its strength exceeds the weathering and erosion processes (e.g., gentle slope, clay soil).
32
What is an unstable slope?
A slope is unstable if slope materials are weaker than the weathering and erosion processes (e.g., steep slope, sand soil).
33
What are Weathering Processes?
Weathering processes break down rock at Earth’s surface and to some depth below the surface, either disintegrating rock into particles or dissolving it in water. Two types of weathering processes:
34
Explain Physical Weathering:
Physical weathering process, also called mechanical weathering, is the process of rock breakage without any chemical alteration.
35
Explain Chemical Weathering:
Chemical weathering process refers to actual decomposition and decay of the constituent minerals in rock due to chemical reaction, ***always in the presence of water.***
36
Explain Regolith and Soil:
Regolith is the broken-up rock due to weathering. Bedrock is the parent rock from which weathered regolith and soils develop.
37
What are some factors influencing weathering processes (5)?
-Rock composition and structure (jointing)
-Climatic conditions -Subsurface water
-Slope orientation -Vegetation
38
Define a Joint:
Joints are fractures or separations in rock that occur.
39
What does the presence of joints do? and why?
The presence of joints increases both physical and chemical weathering. It increases the surface area of rock exposed to both physical and chemical weathering.
40
Explain Slope Orientation:
Orientation controls slope’s exposure to Sun, wind, and precipitation. Slope faces away from the solar radiation tend to be cooler, moister, and more vegetated than slopes in direct sunlight.
41
What are chemical conditions of weathering?
Precipitation, temperature, and freeze–thaw cycles
42
True or False: Physical weathering dominates in drier and cooler climates.
True
43
True or False: Physical weathering dominates in wetter and warmer climates.
False, Chemical weathering dominates in wetter and warmer climates.
44
What are the four physical weathering processes?
-Vegetation (root expansion)
-Frost action (or freeze–thaw action)
-Salt-crystal growth (or crystallization)
-Pressure-release jointing
45
Explain Vegetative physical weathering;
-Vegetative cover can protect rock by shielding it from raindrop impact. Roots can stabilize soil. Roots also produce organic acids and enhance chemical weathering.
-Plant roots can also break up a rock.
46
Explain Frost Wedging weathering processes:
When water freezes, its volume expands as much as 9%. This expansion produces a powerful mechanical force that can overcome the tensional strength of rock. (water penetrating a crack, expanding and breaking it apart).
47
Provide a scenario of frost wedging:
-Repeated freezing (expanding) and thawing (contracting) of water is frost action, or freeze- thaw, which breaks rocks apart in the process of frost wedging.
48
Explain Salt-crystal growth in terms of physical weathering:
As the water on the surface of rocks evaporates, dissolved minerals in the water grow crystals— crystallization.
49
True or False: Over time, as the crystals grow and enlarge, they exert a force to spread apart individual mineral grains and begin breaking up the rock.
True.
50
Explain Pressure Release Jointing (exfoliating/sheeting) in terms of physical weathering:
intrusive igneous rocks, the rock reaches the surface the pressure releases a bit, so we get cracking or breaking. Exfoliated granite expanding and cracking once it reaches the surface (dome and half-dome).
51
What are Chemical weathering processes?
Chemical weathering refers to the chemical breakdown, always in the presence of water, of the constituent minerals in rock
52
What are two subcategories of chemical weathering?
decomposition and decay
53
True or False: The chemical decomposition and decay become more intense as both temperature and precipitation increase.
True.
54
Give an example of chemical weathering:
One typical chemical weathering is spheroidal weathering
55
What is spheroidal weathering?
Rounding of edges due to chemical weathing
56
Where does chemical weathering occur most?
Chemical weathering most readily occurs in joints and fractures.
57
Chemical weathering is a process of __________ alteration, with some minerals being more susceptible than others.
mineral
58
True or False: mafic igneous rocks are more susceptible to chemical weathering than those rich in felsic minerals (feldspar and quartz).
True
59
What are the dominant processes of chemical change affecting rock forming minerals (3)?
-Oxidation -Hydrolysis -Carbonation
60
What are oxidation and hydrolysis?
Change the chemical structure of primary minerals, turning them into secondary minerals that are typically softer and bulkier and therefore more susceptible to erosion and mass movement.
61
____________ by oxidation and hydrolysis changes rock-forming minerals into oxides and clay minerals.
Decomposition
62
What is Oxidation?
Decomposition of chemical compounds by reaction with oxygen (O2) Fe2+ + O2 ----- Fe3+ 2O3
63
What is an example of oxidation?
-Iron Oxide (aka Rust)
64
What is Hydrolysis?
Decomposition of chemical compounds by reaction with water, ending up with a different result in the end. (H2O) 2 KAlSi3O8 + 2 H2CO3 + 9 H2O ⇌ Al2Si2O5(OH)4 + 4 H4SiO4 + 2 K+ + 2 HCO3 −
65
What is an example of Hydrolysis?
-Feldspar (K, Al, Si, O) + carbonic acid + water ⇌ residual clays + dissolved minerals + silica
66
_______________ weathering through acid action is mainly associated with carbonic acid (H2CO3) formed when CO2 dissolves in water.
Chemical
67
What two chemical weathering processes shape landscapes?
Carbonation and Dissolution
68
How is carbonic acid formed?
Chemical weathering through acid action is mainly associated with carbonic acid (H2CO3) formed when CO2 dissolves in water.
69
What type of dissolved chemical are found in Rainwater, soil water, and stream water?
CO2
70
True or False: Percolating water is primarily acidified as it moves through the soil and reacts with CO2 generated by decomposition of organic material.
True.
71
What process of carbonation is critical in the intermediate stage of weathering of igneous rocks?
Carbonic acid slowly interacts with feldspars and other types of minerals to form carbonates
72
Limestone and marble are particularly
_________ to acid action
susceptible
73
Explain Limestone dissolution by groundwater:
In moist climates, the slow flow of groundwater in the saturated zone can dissolve limestone below the surface, producing large underground caverns.
74
What happens when caverns collapse?
causing the ground above to sink and a unique type of karst landscape to develop.
75
_____________ are interconnected subterranean cavities in bedrock formed by the corrosive action of circulating groundwater on limestone.
Limestone caverns
76
What is a Sinkhole?
A sinkhole is a surface depression in a region of cavernous limestone.
77
What is the process of a sinkhole?
Surface is getting weaker due to erosion, it eventually collapses.
78
What is Karst Topography?
The karst topography refers to a limestone (very common at the surface) region with a specific landscape of pitted, bumpy surface topography, poor drainage, and well-developed solution channels underground, due to chemical weathering.
79
What are prominent Karst features?
Sinkholes Caves and Caverns
80
Where do sinkholes form?
Circular Depressions
81
Define Mass Movement Mechanics:
Physical and chemical weathering processes weaken the surface of the landscape and make it more susceptible to the pull of gravity.
82
Define the Angle of Repose:
The larger the slope angle, the higher the chance of mass movement. The (slope) angle of repose represents a balance between the driving force (gravity) and resisting force (friction and cohesion).
83
What is the driving force in the Angle of Repose?
Gravitational force
84
What is the restricting force in Angle of Repose:
Friction and Cohesion
85
True or False: In any mass movement, gravity pulls on a mass until the critical shear-failure point is reached.
True
86
______________: gravity pulls on a mass until the critical shear-failure point is reached.
geomorphic threshold
87
What are the three types of geomorphic threshold?
fall, slide, or flow.
88
Give an example of a Geomorphic threshold fall:
A rockfall is a volume of rock that falls through the air and hits the surface.
89
Give an example of a Geomorphic threshold slide:
A sudden rapid movement of a cohesive mass of regolith or bedrock that is not saturated with moisture is a landslide
90
What are the two kinds of landslides?
Translational slide
Rotational Slide
91
What is a Translational Slide?
translational slides (downslope)
92
What is a Rotational Slide?
rotational slides (rotation of material, slumps)
93
What happens when soil is saturated?
it will flow
94
What do Flows include?
Flows include earthflows and more fluid mudflows.
95
What is a Soil Creep?
On most slopes, soil and regolith move extremely slowly downhill through the process of soil creep. Soil creep occurs through the effect of some process of soil disturbance acting under the influence of gravity (dry soil).
96
Is soil normally wet or dry in soil creeps?
Dry
97
At what speed do soil creeps move?
Very Slow (creeping)
98
What are some disturbances of soil and regolith?
Alternate wetting and drying of the soil, freeze / thaw, heating and cooling of the soil, trampling and burrowing by animals, and shaking by earthquakes
99
Where do we find earth flows and rotational slumps?
In humid climates
100
What is the process of earth flow?
a mass of moist soil and fine regolith may move down a steep slope in the form of an earth flow. (Often referred to as a landslide).
101
True or False: ***The rate at which an earth flow develops can be slow or rapid, depending on the texture of the material, moisture content, and angle of slope.***
True.
102
Define a Slump:
Water percolates deep into a mass of unconsolidated material, resulting in it dropping along a concave slip plane (slow movement along a surface of weakness).
103
One of the most spectacular forms of mass wasting and a potentially serious environmental hazard is the ___________.
mudflow
104
Do mudflows move fast or slow?
Very fast!
105
Where do mudflows usually occur?
These streams of muddy fluid pour swiftly down canyons in mountainous regions.
106
How do mudflows fluctuate?
Mudflows vary in consistency, from a viscous fluid like freshly mixed concrete to fast-flowing, water saturated mixtures of mud and rock.
107
What are fluid type mudflows called?
Debris Flow
108
Define a Landslide:
A landslide is the rapid sliding of large masses of bedrock or regolith.
109
How do landslides differ from mudflows and earth flows?
They are triggered by earth tremors or sudden rock failures rather than by heavy rains or floods; they can also result when excavation or river erosion over steepens a slope.
110
What are Landslides consisted of?
Landslides can range from rockslides of jumbled bedrock fragments to bedrock slumps in which most of the bedrock remains intact as it moves.
111
What are Bedrock Slumps?
Jumbled bedrock fragments remaining intact as it moves.
112
How do Human Induce Mass Movement?
-Highway roadcut
-Surface mining
-Housing development
-Forest clear-cut
113
What are some impacts of mass wasting?
Damage to infrastructure and property ~ $200 – 400 million / yr. in Canada Impact water quality.
--Damage to wildlife and wildlife habitat Land and aquatic Injury or loss of human life Over 650 Canadians over the last 250 yrs. Approx. 43% in BC.
114
What are some Main Environmental Drivers of Mass Wasting?
heavy precipitation
runoff
stream erosion
earthquakes
human activity
115
How does water play a role in mass wasting?
By eroding, undercutting, weathering, loading, or oversaturating.
116
What is the most common trigger of mass wasting?
The most common trigger = increased slope water content.
117
How has precipitation changed in Canada?
-↑ in annual precipitation across Canada Overall increase of approx. 7% (low emission scenario). Overall increase of approx. 24% (high emission scenario).
118
How has precipitation changed in Canada?
-As warming progresses, we are likely to see a shift from snow to rain during the spring and fall ↑ in extreme precipitation events.
119
_______ = the most common driver of slope failure
Water
120
________= more slope failure = more mass wasting?
more water
121
True or False: Environmental and human-environmental systems are extremely complex.
True.
122
What are Indirect Impacts of Climate Change?
Post-wildfire debris flows; Forests stabilize the soil, alter how water moves over the landscape, and mediates snowmelt
123
How is warming contributed to climate change?
Warming → increased wildfire → destabilization, increased runoff, and rapid snowmelt → mass wasting
124
How is warming contributed to mass wasting?
Warming → permafrost melt → destabilization, saturation → mass wasting
125
Define Geomorphology:
Geomorphology is the science that analyzes and describes the origin, evolution, form, and spatial distribution of landforms.
126
What happens when a destabilizing event occurs?
a landform may reach a geomorphic threshold, where force overcomes resistance, and the system moves to a new level and toward a new equilibrium state.
127
Define Chemical Weathering:
the chemical decomposition of minerals in rock
128
True or False: Karst topography refers to distinctively pitted and weathered limestone landscapes.
True
129
True or False: In any mass movement, gravity pulls on a mass until the critical shear-failure point is reached
True.
