Geog 103
Topic One
Here are some notes and explanations on the atmosphere and climate change, based on the provided excerpts.
Where Does Energy Come From?
The Sun is the primary source of energy for the Earth’s atmosphere, accounting for more than 99% of the total energy input.
Solar energy is also referred to as radiant energy or solar radiation.
The Earth receives approximately 1370 Wm-2 of solar energy, known as the 'solar constant'.
The remaining less than 1% comes from internal sources like geothermal, tides and volcanism.
Energy is the capacity to do work on matter.
It is measured in Joules (J) or calories (cal).
When considering energy over a period of time, the units are Watts (W) or Horsepower (hp).
There are two basic types of energy: kinetic (energy of motion) and potential (stored energy).
Temperature is a measure of the average kinetic energy of the molecules in a substance.
Earth's Energy Budget
Earth's Energy Budget describes the balance between incoming solar radiation and outgoing terrestrial radiation.
The atmosphere plays a critical role in this balance, absorbing and scattering solar radiation and emitting longwave radiation.
Albedo refers to the reflectivity of a surface. Surfaces with high albedo, like snow, reflect more solar radiation back into space.
Greenhouse gases in the atmosphere absorb outgoing longwave radiation, trapping heat and warming the planet.
This process, known as the greenhouse effect, is essential for maintaining Earth’s habitable temperature.
Atmospheric Structure
The atmosphere is structured into distinct layers based on temperature and function.
Troposphere:
Closest to the Earth's surface, containing about 90% of the atmospheric mass.
Temperature decreases with altitude at a rate of approximately 6.4°C per kilometer (lapse rate).
Most weather processes occur in this layer.
The tropopause marks the upper boundary of the troposphere, with an average temperature of -57°C.
Stratosphere:
Characterized by a temperature inversion, meaning temperature increases with altitude.
This warming is due to the absorption of UV radiation by the ozone layer (ozonosphere).
The ozone layer is critical for protecting life on Earth by absorbing harmful ultraviolet (UV) radiation from the sun.
Chlorofluorocarbons (CFCs), once widely used in refrigerants and aerosols, have been shown to deplete the ozone layer.
Mesosphere:
Temperature decreases with altitude.
The coldest layer of the atmosphere.
Thermosphere:
Outermost layer, gradually merging into space.
Temperature increases with altitude.
Ionosphere:
Located from 80km outwards and absorbs cosmic rays, gamma rays, X-rays, and short UV rays.
Atmospheric Composition
Nitrogen (N2) and Oxygen (O2) are the most abundant gases in the atmosphere, making up approximately 78% and 21% respectively.
Water vapor (H2O), carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and ozone (O3) are variable gases present in smaller amounts but play significant roles in atmospheric processes.
Greenhouse gases include:
Carbon dioxide (CO2):
Released through natural processes like respiration, decomposition, and volcanic activity.
Human activities, particularly the burning of fossil fuels, have significantly increased atmospheric CO2 concentrations.
Methane (CH4):
Emitted from natural sources (wetlands) and human activities (agriculture, fossil fuel extraction).
A potent greenhouse gas, trapping heat more effectively than CO2.
Chlorofluorocarbons (CFCs):
Primarily from human-made refrigerants and aerosols.
Deplete the ozone layer and contribute to the greenhouse effect.
Nitrous oxide (N2O):
Hydrofluorocarbons (HFCs):
Replacements for CFCs with low ozone-depleting potential but still contribute to the greenhouse effect.
Aerosols are solid or liquid particles suspended in the atmosphere.
They come from natural sources like sea spray, dust, and volcanic eruptions.
Human activities, such as combustion, also release aerosols.
Aerosols can influence climate by scattering or absorbing solar radiation and acting as condensation nuclei for cloud formation.
Energy Transfer
Energy is transferred in the atmosphere through three primary mechanisms:
Radiation: The transfer of energy through electromagnetic waves.
Sensible Heat: The transfer of heat energy through the movement of air or water.
Latent Heat: The energy required or released during a change of state (e.g., evaporation, condensation).
Winds
Wind is the movement of air from areas of high pressure to areas of low pressure.
Winds are named based on the direction they originate from (e.g., a westerly wind blows from the west).
The four driving forces that influence wind are:
Gravity: Pulls air downward, creating atmospheric pressure.
Pressure Gradient Force (PGF): The difference in air pressure between two points, causing air to move from high pressure to low pressure.
Coriolis Force: Due to Earth's rotation, deflects moving air to the right in the Northern Hemisphere and to the left in the Southern Hemisphere.
Friction Force: Opposes wind motion, reducing wind speed near the Earth's surface.
Geostrophic wind results from the balance between the pressure gradient force and the Coriolis force, flowing parallel to isobars.
Surface winds are influenced by friction, resulting in a more complex flow pattern.
Anticyclones are high-pressure systems associated with descending air and clear skies.
Cyclones are low-pressure systems associated with rising air and often stormy weather.
Climate Change
Climate change refers to significant, long-term changes in global or regional weather patterns.
Natural factors influencing Earth’s climate include:
Solar activity cycles: Variations in the Sun's energy output, influencing Earth's climate over long periods.
Milankovitch Cycles: Changes in Earth's orbital parameters (tilt, precession, and eccentricity) that affect the distribution and intensity of solar radiation received over thousands of years, contributing to glacial and interglacial periods.
Atmospheric composition changes: Alterations in the concentrations of greenhouse gases and aerosols, caused by natural events (volcanic eruptions) or human activities (fossil fuel combustion).
Plate tectonics: The movement of Earth’s tectonic plates, influencing the distribution of landmasses and oceans, impacting ocean currents and atmospheric circulation patterns over very long timescales.
Anthropogenic (human-induced) climate change is primarily driven by the increase in greenhouse gas emissions since the Industrial Revolution.
Burning fossil fuels, deforestation, and agriculture are major contributors to rising concentrations of CO2, methane, and other greenhouse gases.
Global warming is the observed increase in Earth's average temperature due to the enhanced greenhouse effect.
Evidence for global warming comes from multiple sources, including rising global temperatures, melting glaciers and ice caps, rising sea levels, and changes in precipitation patterns.
Consequences of climate change are wide-ranging, including more frequent and intense heat waves, droughts, floods, sea-level rise, ocean acidification, and disruption of ecosystems.
Climate models project continued warming throughout the 21st century and beyond, with significant impacts on human societies and natural systems.
Climate Classification
Climate classification systems categorize different regions of the world based on their long-term weather patterns.
The Köppen-Geiger System is one of the most widely used climate classification systems.
This system classifies climates based on:
Temperature: Average monthly and annual temperatures.
Precipitation: Average monthly and annual precipitation.
Seasonality: The distinctness of seasons based on temperature and precipitation.
The five major climate classes in the Köppen-Geiger system are:
A: Tropical moist: Warm temperatures year-round with abundant rainfall.
B: Dry: Arid or semi-arid climates with low precipitation.
C: Moist sub-tropical mid-latitude: Mild winters and warm to hot summers with varying precipitation.
D: Moist continental mid-latitude: Cold winters and warm summers with significant temperature variations throughout the year.
E: Polar: Extremely cold winters and summers with low precipitation.
Please note: This study guide is based on the provided excerpts. It's always advisable to refer to the full course material and additional resources for a comprehensive understanding of the topics.
Topic Two
Here is a study guide covering the topics of Precipitation and Storms, River Systems, and Glacial Processes and Landforms.
Precipitation and Storms
Precipitation (P or PPT) is defined as solid or liquid water that forms under saturated conditions (100% relative humidity) and falls toward Earth. Most clouds do not produce precipitation because the particles are too small. For precipitation to occur, condensation nuclei (dust, etc.) are required for collision and coalescence of droplets. A ‘lifting’ mechanism that causes instability, rising, cooling, and condensation is also required for precipitation to occur.
There are four lifting mechanisms that cause precipitation:
Orographic Uplift and Precipitation: Clouds and heavy precipitation occur on the windward side. The leeward side experiences adiabatic warming and drying, causing a ‘rain shadow’ effect.
Frontal Precipitation: This occurs where two air masses collide, producing a ‘front’. Frontal convergence and uplift cause warm air to rise over cool air. There are different types of fronts, with cold fronts causing heavier precipitation and warm fronts causing more gradual precipitation.
Cold Front: An advancing, cold, dry, stable air mass displaces warm, moist, unstable air. This results in rapid uplift and more violent weather.
Warm Front: An advancing, warm, moist air mass replaces retreating, cold, dry, stable air. This can cause sleet and freezing rain in winter.
Occluded Front: This occurs when cold fronts move faster than warm fronts and overtake them. Warm air is ‘occluded’ (separated) from the cyclone at Earth's surface.
Convergent Precipitation: Large-scale convergence causes air masses to merge towards a low-pressure area (with or without fronts), which results in lifting.
Convective Precipitation: Unequal surface heating causes localised instability and the rise of air masses, leading to cooling and condensation.
The global distribution of precipitation is as follows:
Convective and convergent precipitation occurs near the equator.
Frontal and orographic precipitation occur in mid-latitudes.
There are three main types of storms:
Extra-tropical (mid-latitude) cyclones: These occur in mid-latitudes and can manifest as blizzards, nor’easters, and southeasters. They are often associated with frontal systems. Extratropical cyclones require a strong temperature gradient of air masses, available moisture, and upper air contribution (jet stream divergence).
Tropical cyclones: These have a very low-pressure centre and are generated over warm ocean waters. They are not associated with fronts and have an eyewall of heavy precipitation.
Meso-scale convective thunderstorms: These are organised on a large scale and form when moist, unstable air is lifted rapidly. Condensation occurs and latent heat is released. These storms can cause hail, tornadoes, lake-effect snow, etc.
River Systems
A drainage basin is a central hydrological unit, also known as a watershed. Drainage basins are bordered by drainage divides. Approximately 60% of Canada’s freshwater drains to the north. The total area in Canada covered by fluvial systems is 891,163 km2 (8.9% of Canada).
Stream discharge (Q) is the streamflow volume passing a point in a given unit of time. It is calculated as Q = w d v = A * v, where:
w = width
d = depth
v = velocity
A = cross-sectional area
The unit of discharge is cubic length/time (e.g., m3/s).
A hydrograph is a plot of discharge (Q) over time. Typical flow response patterns on a hydrograph include seasonal storms, flood events, and ground cover effects.
A graded river strives for dynamic equilibrium. It adjusts its profile (slope) to balance the energy required to transport sediment.
Base level is the lowest elevation to which a stream can erode. It is defined by the elevation of the outlet, which can be sea level or local/temporary (e.g., a pond or lake). Changes in base level cause river readjustments. A rise in base level causes deposition, and lowering causes erosion.
Rivers transport sediment through shear stress (τ), which is a force exerted by flowing water on the bed. The amount of sediment moved depends on discharge (Q), velocity (u), slope (θ), and sediment size and availability.
Stream competence is the ability to transport a certain size of sediment and is a function of velocity squared (u2).
Stream capacity is the ability to transport a certain volume of sediment and is a function of discharge (Q).
There are three types of loads in streams:
Dissolved load: This is a chemical solution.
Suspended load: This consists of fine-grained particles.
Bed load: This consists of coarser materials.
Fluvial erosion occurs when sediment output is greater than sediment input, resulting in a net removal of mass. Sediment transport itself is not erosion. Erosion increases with flow speed. Fluvial erosion involves:
Removal of material from the river bed
Entrainment and transport of loose particles
Abrasion and plucking of rocks
Dissolution of soluble rocks
Fluvial erosion results in:
Headward erosion of the channel network
Incision (downcutting) of channels
There are three main types of channel patterns:
Straight
Meandering: Meandering rivers develop in areas with low gradients and fine sediment loads. The thalweg is the fastest flowing region of a meandering river.
Braided: Braided rivers have multiple channels, steep slopes, high, variable discharge, high sediment load (mostly bedload), and unstable bars. They are more common in Canada than meandering rivers and tend to be found in mountainous/glaciated areas. Examples include the Mackenzie, Yukon, and Bow rivers.
Alluvial fans are terrestrial features where a steep stream leaves a narrow valley. The slope outwards in a broad arc.
Deltas are mostly subaqueous features where a stream enters an ocean or lake. Some terrestrial deposition occurs. Channel ‘distributaries’ carry water from the main channel over the delta surface.
Flooding occurs when the discharge (stage height) exceeds the channel banks. This results in the inundation of land not normally underwater (floodplain). Globally, flooding is the most common and destructive natural hazard.
Flooding is caused by both natural and human-induced factors. The four types of flooding are:
Regional: This is caused by high precipitation, snowmelt, or rain-on-snow events.
Flash: This is caused by high precipitation in mountainous, arid, or urban landscapes.
Ice-jam: This is caused by ice damming and flow backup.
Dam failure: This is caused by breaches of dams or levees.
Flood recurrence interval (R, yrs) or flood probability (P, %) can be calculated using R = 1/P. For example, a “100-year flood” has a recurrence interval (R) of 100 and a probability (P) of 1/100, meaning there is a 1% chance of it occurring in any given year.
Flood control methods include:
Artificial levees
Dams
Channelization
‘Soft engineering’
Floodplain management
Glacial Processes and Landforms
A glacier is a large mass of ice resting on land or floating as an ice shelf in the sea adjacent to land. It is a perennial accumulation of snow and ice that flows under its own weight. Glaciers are classified by morphology (size), flow dynamics, and thermal properties.
Glacial systems are open systems that consist of perennial inputs of snow, throughputs of moving ice, and ablation outputs (meltwater/sublimation/calving).
Glacial ice formation occurs in three stages:
Stage 1: Snow survives the summer.
Stage 2: Old snow is slowly pressured and recrystallized into firn, which has a compact and granular texture.
Stage 3: After many years, snow and firn are pressured and recrystallized into a dense glacial ice.
Glaciers have an accumulation zone, where inputs of snow and ice from precipitation occur, and an ablation zone, where outputs occur via melt, evaporation, sublimation, and calving.
Glacial mass balance (Bm) refers to the balance of inputs and outputs of snow, ice, and water. It is calculated as Bm = accumulation – ablation over a given time period. If Bm is greater than 0, the glacier is growing and typically has an advancing terminus. If Bm is less than 0, the glacier is shrinking and typically has a retreating terminus. Most glaciers worldwide have a negative Bm.
Glacial flow occurs through three mechanisms:
Internal plastic flow (creep): This occurs at depth where glacial ice is under pressure and flows under its own weight.
Basal sliding: This occurs in warm glaciers and involves slippage at the base of the glacier. It is sporadic and depends on water.
Subglacial bed deformation: This involves sediment movement underneath the ice.
Ice flow acts as a geomorphic process by scouring and eroding rock. Flowing ice entrains and ‘pushes’ sediment, leading to plucking, quarrying, and abrasion. Glacial meltwater contributes to erosion through meltwater flow (outwash and rivers) and pressurized subglacial flow.
Erosional landforms created by glaciers include:
U-shaped valleys
Arêtes: Sharp ridges formed by erosion on both sides.
Horns: Formed between the headwalls of three or more cirques.
Roche moutonées
Grooves and striations
Depositional landforms created by glaciers include:
Moraines: These are accumulations of glacial till.
Terminal moraine: Marks the furthest advance of a glacier.
Recessional moraine: Built while the terminus recedes and the glacier remains stationary.
Lateral moraine: Forms along each side of a glacier.
Medial moraine: Forms when two glaciers with lateral moraines join.
Glacial outwash plains
Eskers: Sinuously curving, narrow ridges of coarse sand and gravel. They form along the channel of a meltwater stream that flows beneath a glacier, in an ice tunnel, or between ice walls.
Drumlins
Kettle lakes
Glacial erratics: Rocks that have been transported and deposited by glaciers, often far from their source region.
Proglacial lakes
This study guide provides a summary of key concepts and terms related to precipitation and storms, river systems, and glacial processes and landforms. Please note that this is just a starting point, and further research may be necessary to fully understand these topics.
Topic Three and Four
Coastal Processes, Landforms and Hazards
Waves: Waves are a crucial element in shaping coastal environments. They are generated by wind and their characteristics, like height and length, depend on wind speed, duration (how long the wind blows), and fetch (the distance over which the wind blows).
Wind waves are the waves you see at the beach on a windy day.
Swell is formed when wind waves combine and travel long distances. They have a longer period than wind waves.
Tsunamis are seismic sea waves caused by underwater disturbances like earthquakes or landslides. They are not related to tides, despite sometimes being called "tidal waves". Tsunamis have a very long wavelength and travel extremely fast in the open ocean. As they approach the coast, they slow down and increase in height, causing a devastating surge of water.
Tides: Tides are the daily rise and fall of sea level caused by the gravitational pull of the Moon and Sun, and the centrifugal force due to the Earth's rotation.
Spring tides: Occur when the Sun, Earth, and Moon are aligned, resulting in higher high tides and lower low tides (a larger tidal range).
Neap tides: Occur when the Sun, Earth, and Moon are at right angles, leading to lower high tides and higher low tides (a smaller tidal range). The Bay of Fundy in Nova Scotia, Canada, experiences the highest tides on Earth due to its unique shape and resonance.
Coastal Erosion: Coastal erosion is the wearing away of land and the removal of beach or dune sediments by wave action, currents, and wind.
Processes:
Hydraulic action: The force of waves pounding against the shore can break rocks and remove sediment.
Abrasion: Sediment carried by waves grinds against the shoreline, wearing it down like sandpaper.
Corrosion: The dissolving of rock by seawater, particularly in areas with limestone.
Landforms: Erosion creates distinct coastal landforms:
Cliffs: Steep, vertical rock faces formed by wave erosion at the base.
Platforms: Flat areas formed at the base of cliffs as they retreat due to erosion.
Headlands: Areas of resistant rock that jut out into the sea, often forming caves, arches, and stacks due to erosion.
Sedimentary bluffs: Steep slopes composed of unconsolidated sediment.
Coastal Deposition: This occurs when waves and currents lose energy, dropping the sediment they were carrying.
Sediment sources: Rivers, erosion of cliffs and headlands, and offshore sources.
Landforms: Deposition creates various landforms:
Beaches: Accumulations of sand and gravel deposited along the shoreline.
Offshore and intertidal bars: Ridges of sand or gravel formed beneath the water's surface.
Berms: Flat platforms of sand or gravel deposited parallel to the shoreline.
Cusps: Crescent-shaped indentations along the beach.
Spits: Narrow extensions of beach material that project out into the water.
Tombolos: Spits that connect an island to the mainland.
Barrier islands: Long, narrow islands composed of sand that run parallel to the coast and protect the mainland from storms.
Coastal Hazards: Human activities and natural events can pose threats to coastal areas.
Storm surges: An abnormal rise in sea level caused by strong winds and low atmospheric pressure during storms, particularly hurricanes and tropical cyclones. Storm surges can inundate coastal areas, causing extensive damage.
Sea level rise: The long-term increase in global sea level due to thermal expansion of water and the melting of glaciers and ice sheets. Sea level rise threatens coastal communities with inundation, erosion, and saltwater intrusion.
Causes:
Eustatic: Changes in the volume of water in the oceans.
Steric: Expansion of water as it warms.
Geological: Isostatic rebound (the rise of landmasses after the removal of ice sheets), ground subsidence, tectonic motions, and sedimentation.
Tsunamis: As explained above, tsunamis are giant waves triggered by seismic activity. They can travel thousands of miles across oceans and cause catastrophic destruction when they hit coastal areas.
Coastal sensitivity: The degree to which a coast is susceptible to changes caused by sea level rise. Factors influencing sensitivity include geology, morphology, sea level history, wave regime, sedimentation, and tides.
Weathering
Definition: The breakdown of rocks, soil, and minerals through contact with the Earth's atmosphere, water, and biological organisms. Weathering occurs in situ (with little or no movement), and should not be confused with erosion, which involves the transport of rocks and minerals by agents such as water, ice, wind, and gravity.
Importance: Weathering is a fundamental process in shaping the Earth's surface. It forms soil, breaks down mountains, and provides nutrients for plants.
Susceptibility: Metamorphic and igneous rocks are more susceptible to weathering because they were formed under conditions very different from those at the Earth's surface.
Types:
Physical weathering: The mechanical breakdown of rocks into smaller pieces without changing their chemical composition.
Processes:
Frost action (freeze-thaw): Water expands when it freezes, exerting pressure on cracks in rocks, eventually breaking them apart.
Crystallization (salt weathering): Salt crystals growing in cracks and pores of rocks can exert pressure and cause them to break down.
Pressure unloading (sheeting or exfoliation): Rocks formed at depth under high pressure expand and fracture when exposed at the surface.
Thermal expansion: Repeated heating and cooling of rocks can cause them to expand and contract, leading to cracking and disintegration.
Biological weathering: Activities of plants, animals, and microorganisms can contribute to rock breakdown. Examples include tree roots growing into cracks, burrowing animals, and the chemical weathering action of lichens.
Hydration: The absorption of water by minerals, which can cause them to expand and weaken.
Chemical weathering: The breakdown of rocks through chemical reactions that alter the composition of the minerals. Water is often essential for these reactions.
Processes:
Dissolution: Minerals dissolving in water, such as the dissolution of limestone by carbonic acid. This process is crucial in forming karst topography.
Hydrolysis: Reactions between minerals and hydrogen ions (H+) from water, leading to the breakdown of silicate minerals and the formation of clay minerals.
Oxidation: Reactions between minerals and oxygen, often leading to the formation of oxides, such as the rusting of iron-bearing minerals.
Factors Affecting Weathering Rates:
Climate: Temperature and precipitation are key factors. Chemical weathering is more intense in warm, humid climates, while physical weathering is dominant in colder climates with freeze-thaw cycles.
Rock type and mineral composition: The mineral composition and structure of rocks determine their resistance to weathering. For example, quartz is very resistant to weathering, while feldspar is more easily weathered.
Rock texture (porosity and permeability): Rocks with more pores and cracks allow water to penetrate, increasing the surface area exposed to weathering.
Topography (relief, aspect, drainage): Steeper slopes experience more erosion, exposing fresh rock to weathering. South-facing slopes in the Northern Hemisphere receive more sunlight and experience higher temperatures, enhancing chemical weathering.
Vegetation and soil chemistry: Plants can enhance weathering through root growth and the release of organic acids. The pH of the soil also influences weathering rates.
Bowen's Reaction Series and Goldrich Stability Series: These series help predict the weathering susceptibility of minerals. Minerals that crystallize at higher temperatures (early in the series) are less stable at Earth's surface temperatures and weather more rapidly.
Slope Systems and Mass Wasting
Definition: The downslope movement of Earth materials (rock, soil, debris) under the direct influence of gravity. It is a natural hazard that can cause significant damage and loss of life.
Differentiation: Mass wasting processes are classified based on:
Material: Rock, soil, debris, mud, snow, ice.
Speed: From very slow (creep) to extremely rapid (falls).
Causes: Mass wasting occurs when the driving forces (gravity) exceed the resisting forces (friction, cohesion) that hold the material on the slope. It's often triggered by events that increase the driving forces or decrease the resisting forces.
Forces on a Slope:
Driving forces: Primarily gravity, acting on the mass of material on the slope. The steeper the slope, the greater the driving force.
Resisting forces:
Friction: Resistance to movement between the material and the slope surface.
Cohesion: The internal strength of the material holding it together.
Vegetation: Plant roots help bind soil and increase slope stability.
Slope Stability:
Factor of Safety (Fs): The ratio of resisting forces to driving forces. A value greater than 1 indicates a stable slope; less than 1 indicates an unstable slope prone to failure.
Triggering mechanisms: Events that can trigger mass wasting include:
Intense rainfall or snowfall: Water saturates the ground, increasing weight and reducing friction.
Rapid snowmelt: Similar to rainfall, it saturates the ground quickly.
Gradual erosion: Undercutting of slopes by rivers or waves can make them unstable.
Loss of anchoring vegetation: Deforestation or wildfires can remove the stabilizing effect of plant roots.
Earthquakes: Vibrations can trigger slope failure.
Volcanoes: Eruptions can cause landslides and debris flows.
Human activities: Construction, mining, and improper land management practices can increase slope instability.
Role of Water in Mass Wasting:
Reduces interparticle friction: Water lubricates the soil particles, making them less tightly packed and more prone to movement.
Acts as an erosive agent: It can remove material from the base of slopes, increasing steepness and instability.
Adds weight: Water-saturated soil is much heavier than dry soil, increasing the driving force for mass wasting.
Increases pore water pressure: Water in the pores of the soil exerts an outward pressure that can push particles apart and reduce the strength of the material.
Dissolves cohesive agents: Water can dissolve minerals that bind the soil together, weakening it.
Types of Mass Wasting:
Creep: Slow, gradual downslope movement of soil or rock. It is often imperceptible except over long periods. Evidence of creep includes tilted fences, curved tree trunks, and cracked walls.
Slumps: Downslope movement of a coherent mass of material along a curved failure surface. The top of the slump usually tilts backward, creating a scarp.
Flows: Movement of material with a high water content, behaving like a viscous fluid. Examples include earthflows (slow) and debris flows (rapid).
Slides: Rapid downslope movement of material along a planar surface. The material often remains relatively coherent during the slide.
Falls: The free fall of detached rock fragments from a cliff face. Rockfalls occur when the rock is weakened by weathering and eventually breaks loose.
Avalanches: Rapid downslope movements of snow and ice, often triggered by a sudden release of stress or a loud noise. They can reach speeds of over 100 km/h and are extremely dangerous.
Biogeography
Definition: The study of the distribution of species, organisms, and ecosystems in geographic space and through geological time. It seeks to understand why organisms are found where they are, and how their distributions have changed over time.
Approaches:
Historical biogeography: Focuses on the long-term evolutionary history of species and how their distributions have been shaped by continental drift, mountain building, and other geological events.
Ecological biogeography: Examines the relationships between organisms and their current environments, including climate, soil, and interactions with other species.
Ecosystems: A community of living organisms (biotic components) and their physical environment (abiotic components) functioning together as a unit.
Components:
Producers (autotrophs): Organisms that produce their own food through photosynthesis, such as plants and algae. They form the base of the food chain.
Consumers (heterotrophs): Organisms that obtain energy by consuming other organisms. They include:
Herbivores: Plant eaters.
Carnivores: Meat eaters.
Omnivores: Eaters of both plants and animals.
Decomposers: Organisms that break down dead organic matter and release nutrients back into the ecosystem. Fungi and bacteria are the primary decomposers.
Abiotic environment: Non-living components of the ecosystem, such as climate, soil, water, and sunlight.
Biomass and Energy Flow:
Biomass: The total mass of living organisms in a given area.
Primary productivity: The rate at which producers convert solar energy into chemical energy through photosynthesis.
Secondary productivity: The rate at which consumers convert the energy from producers into their own biomass.
Energy flow: Energy flows from producers to consumers to decomposers. Only about 10% of the energy from one trophic level is transferred to the next, with the rest lost as heat. This explains why there are fewer organisms at higher trophic levels.
Species Interactions:
Habitat: The specific environment in which an organism lives.
Ecological niche: The role or function of an organism in an ecosystem, including its interactions with other species and its use of resources.
Fundamental niche: The full range of environmental conditions and resources that a species could potentially use.
Realized niche: The actual range of conditions and resources used by a species, which is often smaller than its fundamental niche due to competition and other interactions.
Types of interactions:
Competition: Occurs when two or more species require the same limited resources.
Predation: One species (the predator) kills and consumes another species (the prey).
Herbivory: Consumption of plants by animals.
Allelopathy: The release of chemicals by one plant species that inhibit the growth of other plant species.
Symbiosis: A close and long-term interaction between two different species. Types of symbiosis include:
Commensalism: One species benefits, while the other is neither harmed nor helped.
Mutualism: Both species benefit from the interaction.
Parasitism: One species (the parasite) benefits at the expense of another species (the host).
Processes Affecting Species Distributions:
Evolution: The change in the genetic composition of populations over time. Evolution can lead to the development of new species and the adaptation of existing species to new environments.
Speciation: The process by which new species arise from existing species.
Modes of speciation:
Allopatric: Speciation occurs when populations are geographically isolated, preventing gene flow.
Peripatric: A small group of individuals colonizes a new area, leading to genetic divergence and potentially speciation.
Parapatric: Speciation occurs in adjacent populations that experience different selective pressures but still have some gene flow.
Sympatric: Speciation occurs within the same geographic area, often due to ecological specialization or the exploitation of new niches.
Artificial: Humans can create new species through selective breeding and genetic modification.
Dispersal: The movement of individuals or their offspring away from their birthplace. Dispersal expands the range of a species and is essential for colonizing new habitats and recovering from disturbances.
Extinction: The complete disappearance of a species from Earth. Extinction is a natural process, but human activities are currently accelerating extinction rates.
Climate Controls on Species Distributions:
Sunlight: Duration, intensity, and quality of sunlight are crucial for photosynthesis and plant growth. Animals are also influenced by sunlight, with some species being diurnal (active during the day) and others nocturnal (active at night).
Moisture: Availability of water is a major limiting factor for many species. Plants have various adaptations to cope with water scarcity, such as drought-tolerant leaves and deep roots.
Temperature: Influences metabolic rates and the distribution of both plants and animals. Some species have specific temperature ranges they can tolerate.
Soils and Nutrient Availability: Soil is the foundation for terrestrial ecosystems. It provides nutrients, water, and support for plants.
Soil components:
Inorganic materials: Weathered rock fragments and minerals.
Organic matter: Decaying plant and animal remains.
Water: Essential for plant growth and soil processes.
Air: Occupies pore spaces in the soil.
Soil-forming processes:
Additions: Organic matter, water, minerals, and gases from the atmosphere.
Transformations: Chemical and physical weathering of minerals, decomposition of organic matter.
Translocations: Movement of materials within the soil profile, such as leaching of minerals downward by water.
Losses: Erosion, leaching, and the uptake of nutrients by plants.
Controls on soil development:
Parent material: The type of rock or sediment from which the soil forms.
Topography: Slope and aspect influence drainage, erosion, and sunlight exposure.
Climate: Temperature and precipitation affect weathering rates, organic matter decomposition, and soil moisture.
Organic activity: Plants and soil organisms contribute to soil structure, nutrient cycling, and organic matter content.
Time: Soil development is a slow process that takes centuries or millennia to reach maturity.
Soil horizons: Distinct layers that develop in a soil profile due to the processes of soil formation.
Biomes: Large-scale ecosystems characterized by distinct climate, vegetation, and animal communities.
Major terrestrial biomes:
Tropical rainforest: Warm, humid, and with high biodiversity. Located near the equator.
Tropical savanna: Warm with distinct wet and dry seasons. Characterized by grasslands and scattered trees.
Desert: Hot and dry with sparse vegetation. Plants and animals have adaptations to conserve water.
Chaparral: Mild, wet winters and hot, dry summers. Vegetation is adapted to fire and drought.
Grassland: Temperate climates with moderate rainfall. Dominated by grasses and few trees.
Temperate deciduous forest: Moderate temperatures and rainfall with distinct seasons. Trees lose their leaves in autumn.
Temperate boreal forest (taiga): Cold, snowy winters and short summers. Dominated by coniferous trees.
Arctic and alpine tundra: Cold and treeless with permafrost (permanently frozen ground). Vegetation consists of low-growing plants like mosses, lichens, and dwarf shrubs.
Climate Change and Biome Shifts: Climate change is altering temperature and precipitation patterns, causing shifts in biome distributions. Species are migrating to higher latitudes and altitudes to find suitable conditions.