GEOG272 Final Review Cards.xlsx - Sheet1 (1) Flashcards
The word slope is used to refer to two different things in the context of geomorphology. Can you define both of them?
Slope can refer to the average angle of inclination on a feature. It can also refer to the character and features of elevated landforms.
Why are slope profiles so useful in analyzing slopes? Can you give some examples of overall qualities and individual features you might find on a slope profile?
Slope profiles give us an accessible overview of the features of a slope, showing us characteristics like if it’s convex or concave or straight, if it breaks/plateaus somewhere, etc.
What is the safety factor (Fs)? What does its value tell us about the state of a slope?
The safety factor is a value that can be calculated through a complex set of equations involving the coulomb equation and the shear strength and stress of a slope. The value of the safety factor tells us about how close the slope is to failure – whether there is danger of collapse or wasting.
What are some ways that shear stress can be affected by environmental changes? Give examples of both increases and decreases.
Shear stress can be increased if the relief of the landscape is increased in any way, if there is addition of mass, by earthquakes, through removal of underlying support from mining or chemical weathering, by tilting of tectonic plates, or by pressure from swelling and freezing of the landscape. It can be decreased through weathering reducing relief of the landscape, by increased pore water pressure in soil lending additional structural support, or by other structural changes in the soil that bolster the resistive framework.
What is a talus? What is the angle a talus forms at called?
A talus is the conically shaped pile of rocks that sometimes forms at the base of a cliff or slope due to the flow of debris downwards. The angle of the talus’ cone shape is called the angle of repose.
Define “flows” in the context of wasting, and describe how fluids can alter the pattern of flow.
Flows are the movement of nonuniform masses of debris, wet or dry. Flows move by inter-particle shearing, like a fluid. Their movement is often aided by a fluid – usually water, but sometimes air.
Define unrestrained slope.
An unrestrained slope is an exposed ground surface that stands at an angle with the horizontal.
Define mass wasting.
Mass wasting is the downslope transport of sediment or other material by gravity.
Define shear and normal stress.
Looking at an object on a slope, the force of gravity pulls down at an angle, and this force can be split into components that are perpendicular and parallel to the slope surface. The component force that is parallel to the slope surface is called the shear stress, while the component that is perpendicular to the slope is called normal stress.
Give a basic definition of hill-slope hydrology.
Hill-slope hydrology is the study of the interactions between water and slopes, including the patterns and processes that emerge out of these interactions and the landforms they create. Most importantly, it often involves looking at the systems of water flow that are established by the relief of the landscape, including drainage basins, the streams and rivers within them, how water makes its way to these streams, et cetera.
What is a storm unit hydrograph? Can you sketch a basic one?
A storm unit hydrograph shows the discharge from streams over time, typically starting before a rainfall event. The profile of the curve shows both how long it takes rainfall water to reach the river system (how long to reach peak discharge) and how long the water stays in the stream system before being moved into higher-order streams or other systems. Using hydrographs, we can extrapolate a wide variety of information about the system, like infiltration capacity of soils, interception of precipitation by plants, et cetera.
What is a drainage basin? What are the two ways water can run through it?
A drainage basin is an area of land where all water and precipitation contribue to the same over-arching system of stream and river flow. Water can move through drainage basins on the surface of the land (surface flow, either by runoff or discharge), or below the surface of the land, as groundwater flow. The groundwater input into a river is called the baseflow.
How is soil important to determining the hydrologic character of an environment?
The properties of the soil influence how much water the soil can hold (infiltration capacity) as well as how fast water can move down into the soil (infiltration rates), and both of these are important factors in determining where water will flow in a system. If infiltration rates are very high, more water will percolate into the groundwater system, and there will be more groundwater movement of water. In an urban system, where infiltration rates are very low (due to tarmac surfaces etc) most water flows over the top of the landscape as overland flow.
As water flows down a slope, it creates certain features. What are these features?
Near the top of a slope, we often see small channels formed by the water flow, which are called rills. As you go downslope, these channels often combine into larger ones called gullies.
We covered four types of hill-slope erosion in class. What are they?
The four types are rill erosion, gully erosion, sheet wash erosion, and rain splash erosion.
Define the following terms having to do with soil moisture: field capacity, wilting point, infiltration, capillary vs saturated flow, runoff vs throughflow vs interflow, percolation, water table.
Field capacity is the amount of water that can theoretically be held by a field or landscape. The wilting point is the amount of moisture content of the soil at which point (or below it) plants will wilt and perish. Infiltration capacity is the amount of water soil can hold before it is saturated, and infiltration rate is the rate at which water moves downward through the soil. Capillary flow is flow of water through soil along membranes of water that form around each soil particle, while in saturated flow, the membranes cease to exist as all space between the soil particles is filled with water. Runoff is flow of water on top of the soil, throughflow is flow in the soil, and interflow is flow of water below the soil (in the groundwater system). Percolation is the process through which water moves down through the soil into the groundwater system. The water table is the point deep in the soil at which groundwater saturates the soil.
What is an interfluve?
An interfluve is the higher-ground land area between two river valleys.
What is a drainage divide?
The drainage divide is the line at separates two drainage basins. Sometimes the drainage divide can be visible, as an elevated feature like a mountain could serve as the dividing point between two drainage basins.
What is a river valley?
A river valley is the lower-elevation area (usually sandwiched between two elevated features) that contains the river.
What is a river terrace?
River terraces are the flat features on either side of the river, generally more elevated than the floodplain.
What are levees?
Raised features on the side of a river or stream that help keep the water within them. They can be natural, formed by deposition of sediment at the sides of the river, or they can be artificial.
What is a flood? What is the area that water floods onto called?
A flood is an event caused by introduction of excess water into a system in which the flow in a channel exceeds its capacity, causing water to spill out onto an area around the stream called the floodplain.
What is the stream order system, and how does it work? What is another name for a first order stream?
The stream order system classifies streams based on how many tributaries exist upstream of it. A first order stream has no tributaries, and is also sometimes called a headwater stream. A second order stream has two tributaries, and so on.
What is drainage density? What is a bifurcation ratio?
Drainage density is the ratio of the total length of streams in a watershed to the total area of the watershed. A high drainage density indicates more streams over the landscape, and thus a quicker response and drainage in storm events. The bifurcation ratio is the ratio of number of streams of a given order to the number of streams of the next highest order. A high bifurcation ratio means that the stream system branches a lot.
Define and compare/contrast: consequent river vs subsequent river vs antecedent river vs superimposed. Provide sketches if you can.
A consequent river forms as a direct result of the relief and shape of the landscape. In a consequent river, water flows in the same direction as the general relief of the landscape. The river is literally a “consequence” of the slope. A subsequent river is one where the water does not flow down the slope of the landscape, instead following other channels. An antecedent river is one that existed and established its channel before some event caused uplift and altered the relief of the landscape. Finally, a superimposed river is one where the stream pattern has been superimposed onto a newly uncovered landscape.
What is a nick point (sometimes spelled knick)?
A nick point is a point in a stream or river at which the elevation suddenly drops, typically due to the end of a layer of rock more resistant to erosion. Depending on the height of the drop and the angle, this can form features like rapids or waterfalls.
What is a base level?
As streams go downhill, their elevation (and thus the potential energy of the water) decreases. The limiting level below which a stream lacks the energy to erode the land is called the stream’s base level. It’s typically sea level, except when streams exist in closed, interior basins that do not interact with the sea.
What does a cross profile of a meandering river show us better? How does it reveal more about the processes at work? Include precise terminology associated with meandering rivers.
The cross-profile view of a meandering river shows that depth is not a uniform semi-circle throughout; instead, at the most extreme point of a bend (called the cut bank) there is a significant distortion of the semi-circle towards the cut bank. The lower velocity of the other side (called the point bar) means that more sediment is deposited here, leading to shallower water on the point bar side and deeper water on the cut bank side.
Give an example for each channel pattern we talked about of where you might find them in nature, and why the qualities of that environment lend themselves well to formation of that pattern.
Meandering streams are often found over sediment (alluvial vallies). This is because the sediment base is easily moulded into a meandering river shape over time. Sand from the bed of the river is entrained during times of higher discharge/water velocity, and sand tends to be deposited into zones of lower velocity (the “inside track” or point bar of a bend). This pattern only amplifies itself over time, as a bend becomes more and more extreme, the difference in water velocity in the point bar compared to the cut bank will increase. Straight streams are most often found atop bedrock, which is more resistant to the kind of deformations that would lead to a meandering stream forming. Braiding streams are usually found atop gravel, which is deposited into gravel bars that often form the islands that make the stream braiding.
Define critical velocity and define the difference between laminar and turbulent flow. What are “laminar” and “turbulent” examples of?
The critical velocity is the speed of fluid flow at which point the motion of the particles changes from laminar to turbulent. In laminar flow, the velocity at each depth is the same and flow can be conceptualized as parallel layers of water moving with one another. In turbulent flow, there is additional uneven resistance to flow introduced into the stream, and as a result, particles move chaotically as their velocities constantly change. Laminar and turbulent flow are both examples of flow regimes, stable patterns of flow that have been observed.
What are the three critical fluvial processes that influence the morphology of river systems?
The three main processes involved are (1) erosion, (2) transport, and (3) deposition.
We talked about 3 main types of erosion seen in bedrock channels in class. Detail each of them.
The 3 types we covered in class are (1) corrosion, which is chemical erosion from solution and hydrolysis, (2) corrasion, which is abrasion and scraping of particles already entrained – it varies with stream power and frictional resistance of bedrock, (3) hydraulic action, which is the stress directly caused from water flowing over the bedrock. Hydraulic action splits further into three more categories – fluid stress, which is caused by wedging from hydraulic action in rapids or waterfalls, cavitation, which is when gas bubbles form and collapse chaotically, sending forceful microjets of water in all directions, and lastly plucking, which is removal of particles by direct pressure of water.
What is the most important concept in understanding erosion and transport in alluvial channels?
Because erosion and transport are overlapping processes in an alluvial channel, and alluvial channels are much lower energy, it’s not practical to try and look at these processes the same way as in bedrock channels. Instead, we mainly look at sediment entrainment and load. The important concept here is competence, which refers to the size of the largest particle a stream can entrain. Competence varies with flow regime, velocity, and sediment characteristics.
What is the “wetted perimeter”?
If you look at a cross-section view of a river, the wetter perimeter is the length along the cross section that is submerged under water. In a very shallow stream, it is typically taken to be the width of the stream. In a deeper stream, it could be something like the width plus twice the average depth.
What is an alluvial fan?
Alluvial fans are deposits of river-transported sediment found at the end of an alluvial river. They typically form when there is a marked break in the slope of the landscape.
What is a delta?
A delta is the landform created when rivers flow into a larger body of water, like a lake or an ocean. The sudden decrease in kinetic energy generally causes the water to deposit its entrained sediment load.
What is a lingoid bar?
Longitudinal bars generally have a pointed end, while lingoid bars are just kind of blob-shaped. This is due to the different ways that sediment is deposited onto them – longitudinal bars are generally made of finer material that is deposited onto the bar as water flows around it, while the lingoid bars are generally much coarser (pebbles and larger) and pick up new material as water tries to flow through or over the bar.
Why is the coastal zone important, what are the driving factors that lead to it being a distinct landform system?
Much of the earth is covered in standing water, which loses little energy as it has little internal resistance. Where this water *does* encounter resistance is when it runs into other matter – like the coastline. The interface between water and the land is the site of energy transfer between these systems, and this transfer of energy generates wave action, creating coastal landforms.
Give a simple definition of wave.
A wave is a periodic disturbance in water level that propagates through water.
What are the five possible mechanisms we covered in class that can lead to wave formation?
The 5 mechanisms are (1) wind, (2) tides from the gravitational energy of the moon, (3) underwater earthquakes, (4) displacement due to gravity, and (5) atmospheric pressure changes.
What is the relationship between wavelength, velocity/celerity of the wave, and the wave period?
V = L/T
What is the difference between semidiurnal and diurnal wave patterns? What about between spring tides and neap tides?
Semidiurnal means that an area experiences two cycles of low-high tide per day, while diurnal means the area only experiences one cycle per day. Spring tides are when the sun and moon are parallel with one another with respect to the earth, resulting in very high and low tides due to their combined distortions. Neap tides are when the sun and moon are perpendicular, resulting in four “bulges” from tidal forces on the earth’s water.
What three factors influence the growth of wind waves?
The wind speed, the “fetch”, and the duration are all important factors. The wind speed is self-explanatory. Fetch refers to the length over which the wind blows uninterrupted on the water’s surface, and the duration refers to the length of time that the wind is blowing.
What is the precise description of how wind waves are formed?
As wind blows, frictional resistance on the water’s surface results in the transfer of energy from the wind to the water, creating ripples. Ripples in turn have a larger area to catch the wind, creating a positive feedback loop that makes the ripples expand in size until they become waves. Since the system (like all systems) seeks to maintain a lowest-energy state, waves (which have more potential energy as they are raised) move towards lower points to try and even out the water’s surface.
What is the difference between sea waves and swell waves?
Swell waves are made in the open ocean, where there are longer distances for the wind to act to create the waves. These waves generally travel faster and have longer wave periods than sea waves, which are shorter waves that are generated closer to shore.
What does the term “fully developed sea” refer to?
“Fully developed sea” refers to the largest size of wave theoretically possible for a specific wind speed, duration, and fetch.
What is shoaling?
Shoaling refers to a series of changes undergone by waves as they begin to break when approaching the shore. Typically, waves become taller, wavelength and speed decrease, and period stays the same. For shoaling to occur, the depth of the water needs to be less than or equal to half the wavelength of the wave. This is because a wave disrupts the water column only to a depth of one half its wavelength.
At what point can a wave no longer support itself?
When H/L = 1/7, the wave becomes unstable and breaks.
What are waves of transition, and waves of translation?
Waves of transition begin to form when waves start to “feel the bottom” and begin to deform. When they begin to break, they are called waves of translation.
What is wave refraction? What is another name for it?
Wave refraction is the reorientation of waves to face in a different direction as they approach a coast, due to different parts of the wave “feeling the bottom” and changing speed at different times than other parts. Another name for this phenomenon is differential shoaling.
What are converging and diverging wave patterns? What are they caused by, and where can we observe their effects most readily?
Both of these patterns are caused by differential shoaling, and they are best observed along a coastline that has headlands and bays, like the ria coast of PEI that we examined for exercise 4. Due to the shape of the landscape and the effects of wave refraction causing waves to generally hit the beach straight on, waves entering a bay will have a diverging pattern to meet the beach in this manner, while waves headed towards the headlands between the bays will form into a converging pattern.
What are the four factors we processes about in class that are the primary factors in coastal erosion?
They are (1) corrasion/abrasion, when waves pick up beach material and hurl them at the base of a cliff, (2) attrition, the wearing down of clasts as they slide back and forth over one another, (3) hydraulic action, when waves hit the base of the cliff and water and air are compressed into cracks, causing fracture (pneumatic quarrying/wave shock) and (4) corrosion/solution, when the rock at the base of a cliff is eroded chemically by weak acids in seawater.
What is “(back)swash”? What process does it contribute to that leads to longshore drift? What is longshore drift, even?
The “swash zone” is the zone of water closest to the sand, and it is the part of the beach where the water surges back and forth over the top of it. When water surges to cover the sand, this is the swash; when the water recedes, this is the backswash. When wavecrests approach at an oblique angle, sediment is transported, because the swash is oblique, but the backswash is always perpendicular to the shoreline.
What are the two kinds of coastal current patterns that we covered?
The two types of coastal currents we talked about are (1) longshore currents, which are responsible for longshore drift and which reflect the component of the wave’s energy that is parallel to the shoreline, and (2) rip currents, which are created by the return flow of water that has piled up near the shore due to breaking waves, forming circulation cells of water near the shore.
What are the seven types of coast we covered in class?
The seven types are (1) ria, when a landscape is submerged, creating many offshore islands, (2) fiord, when a landscape carved by valley glaciers is submerged, (3) barrier island, formed from ridges of sand built by waves, (4) delta, when rivers reach low velocities near oceans and sediment is deposited in a triangular shape, (5) volcanic, when new land is formed from an adjacent volcano (i.e. Hawaii), (6) coral reef atolls, which forms in subtropical environments when volcanoes are eroded down, leaving behind a ring of outer coral reef, and (7) fault, which is a shoreline created as a result of the land suddenly being raised in a tectonic event.
What are some causes of glaciation in the quaternary period?
Four factors were discussed in class. (1) changing continental positions moving to high latitude or polar locations. Once ice begins to accumulate, it creates a positive feedback loop of polar amplification due to the high albedo of ice. (2) Uplift of continental blocks altering atmospheric circulation, and thus oceanic circulation and structure. (3) Decreased CO2 output due to decreased seafloor spreading. (4) Astronomical factors – changes in rotational and orbital pattern of the earth, distribution of solar radiation, and sunspot activity.
What are the three factors involving earth’s place relative to the sun that influence glaciation patterns?
The eccentricity of the earth’s orbit, its tilt on its axis, and the wobble (procession) of its tilt all affect the distribution of insolation received by different parts of the earth, and thus influence patterns of glaciation.
What is the faint young sun paradox, and how was it resolved?
We know due to the sun’s stage in its lifecycle that in the past, it outputted as little as 70% of the energy it releases today, meaning that this past earth should have been a very icy world. However, we also know that the earth has been even warmer than today in the past. This contradiction was resolved by saying that there were higher levels of greenhouse gases in the atmosphere in these periods, helping keep the earth warm.
Where does our knowledge about past glaciations come from?
We have learned about the history and extent of past glaciations by studying glacial deposits scattered across the landscape. In recent years, analysis of marine sediment has proved more complete than these terrestrial records, however.
What is the precise method through which we can track the history of glaciation using marine sediments?
During periods of glaciation, dissolved oxygen in ocean waters changes to a heavier isotope (O18), because the lighter isotope (O16) is preferentially stored in glaciers.
Diagram: Mass wasting, 3 types
What are the five types of sediment transport in rivers?
Important diagram: Velocity vs Grain Size… when are things deposited, entrained, etc?
Important diagram: landforms created by alluvial rivers
Important diagram: Wave motion
What are the four kinds of breakers we talked about in class, and what conditions lead to their formation?
4th type is collapsing.
Important diagram: Coastal erosional landforms
Important diagram: Coastal depositional landforms
Important diagram: Glacier anatomy – equilibrium line, zones of accumulation and ablation, and terminus
Important diagram: Alpine glacial landforms
Important diagram: Alpine post-glacial landforms
Important diagram: the glaciated landscape
Important diagram: permafrost distribution
Important diagram: trumpet diagram
Important diagram: Permafrost landforms
Important diagram: storm event hydrograph
Important diagram: consequent and subsequent streams
Important diagram: meander anatomy and formation
Important diagram: Coastal currents
Important diagram: flood conditions and bankful discharge
Important diagram: Sheet and rill erosion
Important diagram: mass wasting classification triangle
Important diagram: patterns of drainage
Important diagram: channel patterns
Other two are anastamosing and anabranching.
