Weathering, Karst Landscapes, River Systems, and Ocean Processes

Foundations of Geomorphology

• Geomorphology Definition: The scientific study focusing on the origin, development, and spatial distribution of landforms.
• Endogenic Processes: These are geological processes and phenomena caused by forces originating from within the Earth. Key examples include faulting and volcanic eruptions.
• Exogenic Processes: These are geological processes and phenomena caused by forces acting on or above the Earth's surface. They originate from the atmosphere, hydrosphere, and biosphere. Specific areas of study include:     * Weathering and mass-movement.     * River systems and their associated landforms.     * Landscapes shaped by waves and wind processes.     * Landforms worked by ice and glaciers.
• Landmass Denudation: This encompassing term refers to any process that wears away or rearranges landforms. It includes weathering, mass movement, erosion, transportation, and deposition.     * Drivers: These processes are driven by moving water, air, waves, and ice, all of which are influenced by the pull of gravity.     * Resistance: These processes must overcome the inherent resistance of the Earth’s geological materials.

Weathering vs. Erosion

• Weathering: The process that breaks down rock by either disintegrating it into mineral particles (mechanical/physical weathering) or dissolving it in water (chemical weathering).     * Variables Influencing Weathering:         * Rock composition and the presence of joints.         * Climate conditions, specifically precipitation levels and weather patterns.         * Slope orientation (North, South, East, West directionality).         * The position of the water table and how water moves through the soil.         * The extent of vegetation cover.
• Erosion: This term includes the actual transport of weathered materials to different geographic locations.

Physical Weathering Processes

• Frost Weathering: Occurs when water enters rock cracks and freezes. Water expands by as much as $9\%$ when it freezes, exerting pressure on the rock.
• Salt-Crystal Weathering: Common in arid climates where salt crystals grow inside cracks, eventually prying the rock apart.
• Vegetation Weathering: Most frequently involves tree roots growing into cracks and expanding.
• Exfoliation: A process where rock peels off in sheets after being exposed to the surface, influenced significantly by gravity.

Chemical Weathering Processes

• Hydration: Water combines with minerals in the rock; however, no new chemical compounds are formed during this specific process.
• Hydrolysis: Water chemically breaks down minerals, resulting in a chemical reaction that produces a different mineral entirely.
• Oxidation: A chemical change caused by exposure to air, commonly known as rusting.
• Dissolution of Carbonates: This can produce an acid that wears away rock, frequently resulting in the formation of Karst topography.
• Differential Weathering: The process where different rock types or parts of a rock weather at different rates. Notable examples include:     * Delicate Arch in Arches National Park, Utah.     * Hoodoos in Dinosaur Provincial Park, Alberta.

Equilibrium and Thresholds

• Dynamic Equilibrium Model: A state attained in a river when the net effect of flowing water results in neither erosion nor deposition because both processes occur simultaneously and cancel each other out.     * This reflects a balance between the resistance of rocks and the processes acting upon them.
• Steady-State Equilibrium: Characterized by the slow accumulation of small adjustments. An example is the slow uplift and erosion of the Canadian Shield since the glacial ice retreat approximately $12,000\,\text{years}$ ago.

Karst Topography and Limestone

• Limestone Composition: A sedimentary rock composed primarily of calcium carbonate ($CaCO_3$) in the mineral form of calcite.     * Formation: Often organic, forming from shells, coral, algae, and fecal debris in clear, warm, shallow marine waters.
• Karst Topography: A landscape dominated by the dissolution of carbonates.
• Sinkholes: Circular depressions in the ground surface.     * Solution Sinkholes: Formed by surface dissolution.     * Collapse Sinkholes: Formed by the collapse of the roof of an underground cavern.
• Karst Valley: Formed by the coalescence of multiple sinkholes.
• Caves and Caverns:     * Caves: Underground areas large enough for human entry.     * Caverns: Specifically large caves.     * Speleothems: Stalactites are icicle-shaped formations hanging from the ceiling (produced by mineral precipitation from dripping water). Stalagmites grow upward from the cave floor.
• Regional Examples:     * Indiana, USA: Features rolling karst landscapes, ponds in sinkhole depressions, and disappearing streams.     * Eramosa Karst (Ontario): Located in Stoney Creek near the Niagara Escarpment; it displays $16$ different karstic features, including Nexus Cave, and is considered the best example in Ontario.
• Dolomite (Dolostone):     * A sedimentary rock formed by post-depositional alteration of lime mud and limestone by magnesium-rich groundwater (calcium-magnesium carbonate).     * Extremely hard and resistant to erosion.     * Forms the caprock of Niagara Falls and the Niagara Escarpment (specifically Lockport Dolomite).

Mass Movements

• Definition: The downslope movement of material (soil, sediment, or rock) propelled by gravity.
• Required Factors: Slope/Gravity, Debris content, Moisture content, and Surface Resistance.
• Classification by Dynamics:     * Rock Falls: Rocks falling through the air.     * Debris Avalanche: Rock and soil traveling at high velocity due to fluidization by ice or water.     * Landslides: Sudden, rapid movement of a cohesive mass of regolith or bedrock not saturated with moisture.     * Mudflows: High moisture content in the moving material.     * Soil Creep: Persistent, gradual mass movement of surface soil.
• Forces on a Slope:     * Particles possess potential energy due to their position.     * Forces promoting motion: Gravity (aided by endogenic and exogenic events like earthquakes or heavy rain).     * Forces opposing motion: Friction, cohesion, and inertia.     * Potential energy becomes kinetic energy when movement occurs at the geomorphic threshold.
• Scarification: Human-induced mass movement and land alteration. Human activity (mining, clear-cutting forestry) is estimated to be a greater geomorphic agent than all natural processes combined.

River Systems and Fluvial Geomorphology

• Fluvial Geomorphology: The study of the form and function of streams and their interaction with the landscape.
• Drainage Basin (Watershed): The portion of the landscape from which a stream receives water. Major basins comprise smaller sub-basins.
• The Great Lakes: Represent the largest body of fresh water on Earth, accounting for $\frac{1}{5}$ ($20\%$) of the planet's freshwater surface.
• Riverside Terminology:     * Headwater: The source of a river.     * Tributary: A stream flowing into a larger stream.     * Confluence: The junction where two rivers meet (e.g., the West Humber River and Humber River in North West Toronto).     * Mouth: Where the river enters a lake or ocean.
• Drainage Patterns: The arrangement of channels, with the "Dendritic Pattern" being the most familiar.
• Fluvial Processes:     * Erosion: Removal of material by dislodging or dissolving.     * Transport: Movement of material as dissolved, suspended, or bed load.     * Deposition: Setting down the transported material.
• Channel Morphology:     * V-Shaped Channels: Created by steep slopes (high velocity) and high water volume.     * Interlocking Spurs: Ridges of resistant rock that force a river to swing side to side in its upper course.
• The Grand Canyon Example:     * Depth: $1,800\,\text{meters}$ ($6,000\,\text{feet}$).     * Bottom rock (Schist): Approximately $2 \times 10^{9}\,\text{years}$ old.     * Upper rim rock (Limestone): Approximately $230 \times 10^{6}\,\text{years}$ old.
• Meandering Streams: Characterized by side-to-side curving, low gradients, and a scour-and-fill process where the maximum velocity shifts between banks.
• Niagara Falls Stratigraphy: The caprock is hard Lockport Dolomite. Below it lies very soft Rochester Shale, followed by Irondequoit and Reynales Limestone, Neagha Shale, Thorold Sandstone, Medina Sandstone, Power Glen Shale, Whirlpool Sandstone, and Queenston Shale.

Depositional Landforms

• Alluvium: Unconsolidated clay, silt, sand, gravel, and mineral fragments deposited by running water. Sorting occurs during accumulation.
• Floodplain: Low-lying ground adjacent to a river formed of river sediments and subject to flooding. Annual flooding recharges soil nutrients (historically vital for the Nile River in Egypt).
• Alluvial Fan: A cone-shaped deposit in arid/semi-arid regions where water abruptly loses velocity and creates a braided drainage pattern (e.g., Copper Canyon, Death Valley).
• Sand Spit: A small sandy point projecting from the shore. The Toronto Islands originated as a $9\,\text{km}$ ($5.6\,\text{mi}$) long spit formed by alluvial deposits from the erosion of the Scarborough Bluffs.
• Delta: A nearly level depositional plain at the mouth of a river where velocity slows significantly.
• Estuaries: Transition zones between river and maritime environments containing brackish water.     * Importance: Known as "nurseries of the sea." They are more productive than tropical rainforests and coral reefs.     * Species: Vital for lobsters, oysters, crabs, mussels, clams, scallops, flounder, and cod.

Hydrologic Cycle and Groundwater

• Components: Precipitation, runoff, transpiration, evaporation, and percolation.
• Water Table: The upper surface of the zone of saturation.
• Aquifer: The saturated zone beneath the water table. Currently, water tables are falling because removal rates exceed replenishment rates.

Oceans and Coastal Systems

• World Water Distribution: Salt Water ($98\%$), Fresh Water ($2\%$).     * Freshwater breakdown: Ice ($87\%$), Groundwater ($12\%$), Rivers and Lakes ($1\%$).
• The Five Oceans: Atlantic, Pacific, Indian, Antarctic, and Arctic.
• Salinity: The concentration of dissolved salt. $57$ of the $92$ natural elements are found dissolved in ocean water.
• Ocean Structure:     * Mixing Zone: $2\%$ of ocean volume.     * Thermocline Transition Zone: $18\%$.     * Deep Cold Zone: $80\%$.
• The Ocean Floor (Average depth $3.8\,\text{km}$):     * Continental Shelf: Gradually sloping area bordering continents, width varies up to $1,300\,\text{km}$.     * Continental Slope: A steady incline marking the edge of the shelf.     * Continental Rise: Comprised of river sediments.     * Abyssal Plain: Vast flat plains covered in thick layers of sediment from surface organisms.     * Mid-Ocean Ridge: Undersea mountain peaks running around the world.     * Seamount: Underwater mountains that do not break the surface.     * Trenches: The deepest spots on Earth.
• Mariana Trench:     * Located in the western Pacific; crescent-shaped scar $2,550\,\text{km}$ long and $69\,\text{km}$ wide.     * Maximum depth: $10,994\,\text{metres}$ ($36,070\,\text{ft}$) at Challenger Deep.     * Pressure: $1,086\,\text{bars}$ ($15,750\,\text{psi}$), which is over $1,000$ times standard atmospheric pressure.

Coastal and Marine Ecosystems

• Littoral Zone: Extends from the highest storm waterline on shore to depths of approximately $60\,\text{m}$ where storm waves no longer move sediments.
• Intertidal Zone: The area between high and low tide marks.     * Tide Pools: Isolated pockets of seawater left in the intertidal zone during low tide.
• Salt Marshes: Biologically diverse communities in the upper coastal intertidal zone; they protect coastlines.
• Mangrove Forests: Consist of approximately $80$ species of trees/shrubs adapted to salt water. Roots stabilize coasts, reduce erosion from storm surges, and provide fish nurseries.
• Coral Reefs: Underwater structures built from coral skeletons. Colors come from symbiotic algae (zooxanthellae) living in tissues.     * Importance: House one-third of all marine fish species.     * Threats: Climate change leads to Coral Bleaching (expulsion of algae due to warm water). Increased $CO_2$ leads to ocean acidification (formation of carbonic acid), lowering pH levels.

Ocean Circulation and Climate

• Ocean Gyres: Large circular current systems formed by global wind patterns and Earth's rotation.
• Climate Regulation: Currents act like a conveyor belt, transporting warm water from the equator toward the poles and cold water back to the tropics.
• Thermohaline Circulation: A vast conveyor belt driven by differences in water temperature and salinity. Cold, salty water sinks at high latitudes to feed deep circulation.
• El Niño: A weather phenomenon occurring every $2-7\,\text{years}$. Characterized by a warm ocean current starting near Ecuador and Peru, leading to heavier winter precipitation and catastrophic weather worldwide.
• La Niña: Characterized by unusually cold equatorial Pacific temperatures, appearing every $3-5\,\text{years}$. It favors hurricane formation in the Atlantic and brings colder winters to the Canadian west.

Wind (Eolian) Processes

• Erosion Types:     * Deflation: Lifting and removal of individual particles by wind.     * Abrasion: "Sandblasting" action that grinds and shapes rock surfaces.
• Landforms Created:     * Ventifacts: Pitted and polished rocks.     * Yardangs: Elongated rocks shaped by unidirectional winds.
• Methods of Sand Transport:     * Saltation: Sand bounces slightly above the ground in a turbulent flow.     * Suspension: Grains blown high into the air.     * Creep: Grains collide with others, prompting movement.
• Sand Dunes: Mounds of sand formed along beaches or in deserts.
• Sandbanks Provincial Park (Ontario): Contains the world's largest Baymouth Barrier Dune formation located in Prince Edward County near Picton.