Geo Ultimate Study Guide
Examination Logistics and Required Materials
Curricular Scope: The curriculum encompasses fluvial systems, river landforms, glaciology, and cold-region geomorphology.
Assessment Structure: Evaluation involves true-false questions, multiple-choice items, photographic and diagrammatic landform identification, geographic river cartography/mapping, and short-answer analytical problems.
Required Equipment:
Pencil and eraser.
Scantron form type E (distinguished as the narrow, half-page wide by full-page long sheet).
Stand-alone calculator (the use of smartphones or cellular devices as calculators is strictly prohibited).
Fluvial Systems: Terminology and Drainage Basin Dynamics
Basin and Subbasin: A drainage basin (or watershed) is the entire topographically defined terrestrial area drained by a trunk stream and all of its interconnected tributaries. A subbasin represents a smaller, nested catchment area that drains into a specific tributary within the larger regional watershed.
Drainage Divide and Continental Divide:
A drainage divide is a linear topographic ridge, crest, or elevated boundary line separating adjacent drainage basins; precipitation falling on opposing sides flows into entirely different stream systems.
A continental divide is a major regional divide separating drainage basins that empty into completely different major oceans, gulfs, or endorheic inland seas (e.g., the Great Divide of North America separating Pacific from Atlantic/Arctic drainages).
Confluence: The exact geographic location or junction point where two or more flowing watercourses converge to form a single combined channel.
Tributary: A secondary stream or freshwater river that flows into a larger stream, river, or lake rather than discharging directly into an ocean or sea.
Trunk Stream: The primary, highest-order, master drainage channel within a river system that receives discharge from all lower-order tributaries and conveys it toward the outlet.
Perennial Stream: A permanently flowing river channel that maintains active surface discharge year-round, sustained continuously during dry periods by groundwater baseflow entering through the channel bed.
Intermittent and Anthropogenic Intermittent Streams:
An intermittent stream naturally flows only during specific wet seasons or following precipitation events, drying up when the regional water table drops below the channel floor.
An anthropogenic intermittent stream is a river channel that historically flowed perennially but has been converted into an intermittent or dry wash due to human intervention, such as excessive surface-water diversion, dam retention, or unsustainable groundwater pumping.
Exotic Stream: A perennial river that originates in a humid, well-watered mountainous zone with surplus moisture and subsequently flows through an extremely arid or hyper-arid desert region without disappearing (e.g., the Nile River or the Colorado River). Discharge typically decreases downstream due to extreme evaporation and conveyance losses.
Braided Stream: A stream featuring a wide, shallow, interconnected network of multiple dividing and recombining sub-channels separated by transient islands or gravel/sand bars (braid bars).
Distributary: A branching channel network that diverges away from the main trunk stream and distributes water and sediment outward, typically encountered across deltas and alluvial fans (the morphological inverse of a tributary).
Alluvial Fan: A cone- or fan-shaped terrestrial deposit of water-transported sediment (alluvium) that accumulates at the base of a mountain front where a steep, high-velocity canyon stream abruptly debouches onto a broad, flat valley floor, experiencing a dramatic loss of hydraulic energy.
Natural and Artificial Levees:
A natural levee is an elongated, low, flanking ridge of coarse sediment deposited parallel to channel margins during overbank flooding when floodwaters spill out of the active channel and immediately lose velocity.
An artificial levee is an engineered earthen berm, dike, or concrete floodwall constructed along channel banks to increase channel bankfull stage capacity and protect adjacent floodplains from inundation.
Oxbow and Oxbow Lake: A crescent-shaped body of standing water or abandoned channel loop formed when a meandering river breaches the narrow neck between two loops, isolating the former loop.
Delta: A wedge-shaped depositional landform formed at the mouth of a river where it enters a standing body of water (such as an ocean, gulf, or lake) and deposits its remaining sediment load as velocity drops to zero.
Antecedent Streams and Water Gaps:
An antecedent stream is an established drainage channel that maintains its original path and course across a rising tectonic structure (such as an uplifting ridge, anticline, or mountain range).
A water gap is a deep, notch-like pass or transverse gorge carved directly through a mountain ridge by an antecedent river.
Formation mechanism: Tectonic uplift occurs at a rate equal to or slower than the vertical downcutting (incision) rate of the river. The stream cuts downward into the rising bedrock at an identical pace, slicing through the ridge rather than being diverted.
Hydrodynamics, Sediment Transport, and River Morphology
Slope, Velocity, and Transport Capacity:
Channel gradient (slope) directly controls the gravitational shear stress acting on water: as slope increases, stream flow velocity increases.
As flow velocity increases, stream transport ability increases non-linearly: sediment competence (the maximum particle diameter the stream can transport) scales with the square or higher power of velocity, while sediment capacity (the total volumetric mass of sediment moved past a cross-section per unit time) expands substantially.
The Three Modes of Fluvial Sediment Load:
Dissolved Load: Chemical ions held in true molecular solution derived from mineral weathering (e.g., calcium, bicarbonate, chloride); transported invisibly regardless of flow velocity and only precipitates via chemical reactions or evaporation.
Suspended Load: Fine clastic particulate matter (predominantly clay and silt fractions) held aloft in the water column by upward-directed turbulent fluid eddies; makes up the bulk of sediment transported in major rivers.
Bed Load: Coarser, denser particles (sand, gravel, cobbles, and boulders) that remain on or near the channel bottom, moving downstream via rolling, sliding (traction), or saltation (bouncing).
Sediment Sorting Across Basin Gradient Zones:
Headwater / Upper Zone: High gradient, steep slopes, high flow velocities, and high hydraulic energy. Dominated by vertical channel incision and erosion; bed load consists of poorly sorted boulders and cobbles; finer particles are flushed rapidly downstream.
Transfer / Middle Zone: Moderate gradient and balanced energy. Characterized by sediment transport and lateral channel migration; sediment becomes moderately sorted, consisting largely of gravels and sands deposited across dynamic point bars.
Depositional / Lower Zone: Extremely low gradient, low velocities, and broad valley floors. Dominated by net deposition; bed load drops to medium-to-fine sand, while suspended silt and clay dominate the water column, settling across broad floodplains, backswamps, and deltas.
Sorting Action: Streams act as sorting agents; as water slows, transport competence drops progressively, causing the largest and densest particles to settle first, followed systematically by progressively finer particle sizes.
Graded Stream Dynamics and Equilibrium:
A graded stream is an idealized fluvial system in a state of dynamic equilibrium, where over a multi-year timescale, channel slope, geometry, and cross-section have self-adjusted to provide exactly the velocity necessary to transport the sediment load supplied from the upstream watershed without net aggradation (deposition) or net degradation (erosion).
Feedback mechanism: If an external perturbation occurs (e.g., tectonic base-level drop), the river responds with localized incision; if sediment supply surges, channel deposition steepens the gradient downstream until transport capacity matches the influx.
Categorization of Fluvial Landforms:
Erosional Landforms: Gorges, canyons, V-shaped bedrock valleys, waterfalls, cascades, rapids, cut banks, water gaps, and abandoned meander scars.
Depositional Landforms: Point bars, natural levees, floodplains, mid-channel braid bars, alluvial fans, deltas, and valley alluvium fills.
Meander Dynamics, Valley Evolution, and Floods
Braided River Systems:
Environmental Settings: Typically situated in proglacial outwash plains draining melting glaciers, arid-to-semi-arid mountainous piedmonts, and tectonically active zones with high weathering rates.
Causative Factors: Occur where rivers are overwhelmed by an excessive bed-load sediment supply that exceeds transport capacity, coupled with highly erratic or flash discharge regimes and non-cohesive (unstable) channel banks.
Meandering River Systems:
Zonal Distribution: Confined to lowland transfer and depositional reaches characterized by low topographic gradients, steady continuous discharge, and cohesive banks rich in fine silt and clay.
Absence in Mountain Environments: Steep mountainous terrains exhibit powerful vertical downcutting along bedrock corridors with high lateral confinement; high gradients and low sediment-to-capacity ratios prevent the broad lateral planform instability required to initiate meander loops.
Bank Morphodynamics: Cut Banks and Point Bars:
Outer Bank (Cut Bank): Water encounters channel curvature; centrifugal forces and inertia concentrate the line of maximum flow velocity (the thalweg) against the concave outer wall. High shear stress causes continuous hydraulic undercutting and bank slumping, classifying the cut bank as a purely erosional feature.
Inner Bank (Point Bar): On the convex inner bank, frictional drag slows velocity, causing flow divergence and boundary-layer separation. The resulting loss of transport competence forces coarse sediment out of suspension, accumulating as an accretionary point bar, classifying it as a depositional feature.
Evolution of Meander Loops, Oxbow Lakes, and Meander Scars:
Lateral erosion at the cut bank and concurrent accretion at the point bar cause the amplitude of a meander loop to expand outward and migrate down-valley over time.
As adjacent loops grow, the intervening land corridor (the meander neck) progressively narrows.
During major flood stages, the increased hydraulic gradient and overbank flow prompt the river to breach the narrow neck (chute cutoff), capturing the flow along the shorter, steeper course.
Sediment deposition quickly seals off both ends of the bypassed, abandoned loop, isolating it as a crescent-shaped oxbow lake.
Over time, the stagnant oxbow lake fills with fine clays, silts, organic detritus, and peat, transforming into an infilling marsh and ultimately an arcuate depression known as a meander scar.
Waterfall Genesis via Cap Rock Undercutting:
Certain major waterfalls form where horizontal stratigraphy places a hard, highly durable, erosion-resistant layer of rock (cap rock) over a weak, easily erodible sedimentary layer (such as shale or friable sandstone).
Turbulent plunge-pool hydraulics, swirling cobbles, and spray-induced physical weathering undermine the softer basal unit beneath the fall crest.
The unsupported overhang of cap rock experiences tensile failure and collapses under gravity, driving upstream headward retreat of the waterfall and carving an elongated downstream gorge.
Flash (Upstream) Floods versus Downstream Regional Floods:
Flash (Upstream) Floods: Occur in high-gradient headwater catchments, narrow bedrock canyons, and arid arroyos. Triggered by short-duration, high-intensity localized cloudbursts or dam breaches. Characterized by a rapid hydrograph response (short lag time between rainfall peak and flood crest), high flow velocities, and modest total volumetric runoff. Highly lethal to human life due to suddenness, despite remaining geographically localized.
Downstream (Regional) Floods: Occur across low-gradient trunk streams, wide valleys, and extensive coastal floodplains. Triggered by prolonged regional precipitation, saturated soils, or extensive spring snowmelt over large drainage basins. Characterized by long lag times, slow rises and falls over weeks, and massive cumulative water volumes. Highly destructive to fixed infrastructure, agriculture, and property, but generally associated with lower direct human mortality due to advanced warning times.
Flood Recurrence and Return Periods:
The return period (recurrence interval, ) is the statistical average time interval between flood events that equal or exceed a specified magnitude, calculated from an empirical series of annual peak discharges using , where is the number of observation years and is the rank of the event.
Floods do not occur with cyclic regularity; the return period represents an annual exceedance probability (). A "100-year flood" denotes an event with a () chance of occurrence in any individual year, regardless of recent flood history.
Longer return periods are systematically associated with larger discharge volumes and more severe, higher-magnitude flood events.
Flood Mitigation Structures:
Artificial levees and concrete floodwalls constructed to contain bankfull overflow.
Engineered bypass channels, relief spillways, and floodways designed to divert surplus discharge away from urban centers.
Retention basins, detention ponds, and stormwater catchments built to retard peak runoff in urbanized basins.
Channelization (straightening, deepening, or concrete-lining river beds) implemented to maximize conveyance efficiency.
Environmental and Geomorphic Impacts of Dams:
Societal Benefits: Renewable hydroelectric generation, agricultural irrigation storage, flood attenuation, municipal water reservoirs, and recreational flatwater facilities.
Ecological Problems: Disruption of natural flow regimes, alteration of downstream thermal dynamics, fragmentation of aquatic corridors, and prevention of upstream migration by anadromous fish.
Sediment Starvation Impacts: Reservoirs trap bed-load and suspended sediment. Clear water released below dams possesses unexpended hydraulic energy, scouring downstream channel beds (armoring) and stripping downstream river gravels. The loss of delivered sediment deprives coastal deltas and ocean beaches of sand, triggering accelerated coastal erosion, shoreline retreat, and wetland subsidence.
Dam Removal Case Studies:
Elwha Dam (Elwha River, Washington): The removal of the Elwha Dam and the Glines Canyon Dam between 2011 and 2014 was undertaken to restore ecological processes in Olympic National Park. The dams blocked historical Pacific salmon and steelhead migration for a century. Removal mobilized millions of cubic meters of trapped sediment downriver, rebuilding coastal sandbars, restoring estuarine habitats, and allowing anadromous salmonids to recolonize upstream spawning grounds.
Klamath River Dams (California/Oregon border): A multi-dam decommissioning project (including Iron Gate, Copco 1, Copco 2, and J.C. Boyle dams) designed to mitigate severe water quality degradation, halt toxic cyanobacterial blooms in stagnant reservoirs, restore native tribal subsistence fisheries, and open hundreds of miles of historical spawning corridors for struggling coho and chinook salmon runs.
Glaciology: Ice Formation, Classification, and Dynamics
Glacial Ice Genesis and Definitions:
A glacier is an open-system terrestrial mass of recrystallized ice that forms through the prolonged compaction and accumulation of snow, flowing downslope or outward under the influence of its own weight.
Formation Sequence: Fresh, delicate, low-density snowfall ( air space) compresses under gravitational overburden into granular snow; further burial and refreezing form firn (a transitional granular state with intermediate density); continued compaction forces out pore spaces until transforming into true glacial ice, which is formally defined as impermeable crystalline ice containing an air bubble content of less than .
Periglacial Distinction: Glaciers do not develop in periglacial environments, as these non-glacial cold regions experience total summer ablation of annual snow cover or receive insufficient annual snowfall to build a perennial mass balance.
Glacial Kinematics: Plastic Deformation versus Basal Sliding:
Internal Plastic Deformation (Creep): The dominant mechanism of glacial movement, operating as an internal ductile flow. Pressure from overlying ice allows individual microscopic ice crystals to slip along intra-crystalline shear planes without fracturing. Present throughout all glaciers; some cold-based polar glaciers move solely by plastic deformation.
Basal Sliding: The physical sliding of an entire glacier over underlying bedrock, mediated by a lubricating film of pressurized basal meltwater generated by geothermal heat and overburden pressure. Absent in cold-based glaciers frozen solidly to bed substrates.
Brittle-Ductile Boundary and Crevasses: The upper of a glacier remains cold, rigid, and brittle. Where underlying ice flows rapidly over bedrock steps, around bends, or undergoes extensional strain, the brittle surface tears open along vertical fractures known as crevasses.
Kinetic Rate: Glaciers typically move at rates measured in centimeters per day (), which is significantly slower than gastropod locomotion. Ice within the interior of a glacier moves downslope continuously, even when the terminus is retreating.
Taxonomy and Relative Sizes of Glacial Bodies:
Cirque Glacier: The smallest alpine form, restricted to bowl-shaped amphitheaters carved into mountain heads.
Valley Glacier: A stream-like alpine glacier confined within the bedrock walls of a pre-existing mountain valley.
Piedmont Glacier: A broad, bulbous lobe of ice formed when a constricted valley glacier spills out of a mountain canyon onto an adjacent unconfined, flat lowland plain (e.g., the Malaspina Glacier in Alaska, the world's largest piedmont glacier).
Ice Cap: A continuous dome-shaped ice mass that buries high-elevation mountain peaks or plateaus, covering an aerial extent of () or less.
Ice Field: A large mountainous glacier system where topography remains evident; rugged bedrock mountain ridges, peaks, and nunataks project through the ice cover rather than being fully buried.
Ice Sheet (Continental Glacier): A massive continental-scale ice dome that overwhelms and submerges all underlying regional topography, covering an area strictly exceeding ().
Continental Ice Sheets and Marine Margins:
Global Locations: Earth houses exactly three distinct ice sheets across two landmasses: the Greenland Ice Sheet, the East Antarctic Ice Sheet, and the West Antarctic Ice Sheet. Together, they hold over of all glacial ice on Earth.
Antarctic Scale: The Antarctic continent encompasses an area of , bordered by an annual sea-ice seasonal fluctuation pulse ranging from to .
Nunatak: An isolated, barren, angular bedrock mountain summit or ridge that projects above an surrounding continental ice sheet or ice cap.
Outlet Glacier: A fast-flowing tongue of ice that drains an inland ice sheet or ice cap by funneling through a constricted mountainous bedrock valley, usually discharging into coastal waters.
Tidewater Glacier: A mountain valley glacier whose marine terminus terminates directly in ocean seawater.
Ice Shelf: A thick platform of glacial ice that forms where an ice sheet or outlet glacier flows down into a marine bay or ocean basin and floats on seawater (e.g., the Ross Ice Shelf in Antarctica). Ice shelves calve tabular icebergs characterized by flat tops and steep, vertical flanks.
Iceberg: Any large block of freshwater ice detached from a glacier toe or ice shelf floating in an ocean or proglacial lake.
Glacial Mass Balance and Cryospheric Climate Response
Mass Balance Equation and Glaciological Zones:
Zone of Accumulation: The upper, high-elevation sector of the glacier where annual mass inputs from snowfall, avalanches, and rime exceed annual mass loss.
Zone of Ablation: The lower-elevation sector of the glacier where aggregate ice loss exceeds mass accumulation from snowfall.
Equilibrium Line: The boundary line on the glacier surface where seasonal accumulation precisely equals total ablation (net mass balance is zero).
Terminus (Toe): The furthest down-valley or downslope leading margin of a glacier, situated at the base of the zone of ablation.
Mechanisms of Glacial Ablation:
Calving: The mechanical detachment of solid chunks of ice from the glacial terminus, discharging directly into water as floating icebergs ().
Melting: The phase transition of glacial ice into liquid meltwater caused by environmental temperatures rising above the freezing point ().
Sublimation: The direct thermodynamic vaporization of solid glacial ice into atmospheric water vapor without transitioning through an intermediate liquid phase (); operates at temperatures below freezing in dry, windy environments.
Signed Relationships of Advance and Retreat:
When overall , the net mass balance is positive (); the glacier swells and the terminus undergoes glacial advance downslope.
When overall , the net mass balance is negative (); the glacier loses volume and the terminus undergoes glacial retreat (the toe melts upslope).
Internal ice flow within the body of a glacier is always directed downslope due to gravity, even when the terminus is rapidly retreating upslope.
Atmospheric Warming and Polar Degradation:
Mountain glaciers worldwide exhibit negative mass balances and are retreating in response to anthropogenic atmospheric warming.
Greenland Deterioration: The Greenland Ice Sheet experiences severe negative mass balances driven by expanding summer surface melting, decreasing surface albedo (due to dust, soot, and melt puddles absorbing solar radiation), and the rapid acceleration of marine-terminating outlet glaciers, many of which have doubled their flow velocities.
Antarctic Ice Shelf Collapse: Marine ice shelves flanking the Antarctic perimeter act as structural buttresses, pinning outlet glaciers against bedrock thresholds. Elevated ocean temperatures erode ice shelves from below, while surface meltponds induce catastrophic hydrofracturing, causing ice shelves to disintegrate.
Dynamic Consequences: Once an ice shelf disintegrates, the buttressing backpressure is removed, allowing the inland outlet glaciers to accelerate toward the sea, displacing seawater and driving global sea-level rise.
Sea Level Rise Metrics:
Global eustatic sea level is rising at a rate of ().
Dynamic discharge and meltwater runoff from Greenland and Antarctica account for approximately one-third of this ongoing sea-level rise.
Predicting cryospheric response remains challenging because ice-sheet dynamics exhibit non-linear threshold behaviors.
Globally, over people reside in coastal settlements situated at elevations within () of the local high-tide line.
Glacial Landforms: Erosional and Depositional Features
Erosional Mechanics: Plucking and Abrasion:
Plucking (Quarrying): Meltwater penetrates bedrock fractures at the glacier base, freezes, and expands (frost wedging). As the glacier moves, shattered blocks of bedrock freeze into the basal ice and are pulled away from the parent formation.
Glacial Abrasion: The mechanical scouring and gouging of bedrock by rock fragments and coarse clasts embedded within the basal ice of a flowing glacier.
Products of Abrasion:
Glacial Striations: Parallel linear scratches and grooves carved into exposed bedrock parallel to ice flow direction.
Glacial Flour: Silt-sized rock particles produced by the crushing and grinding of rocks against bedrock, which suspends in water to give proglacial lakes a turquoise or milky hue.
Glacial Polish: A smooth, reflective rock surface produced when fine glacial flour acts as an abrasive compound against bedrock.
Alpine Erosional Landforms:
Cirque: An amphitheater-like, bowl-shaped bedrock depression with steep headwalls situated at the head of a glaciated mountain valley, excavated by a cirque glacier.
Tarn: A small, cold mountain lake that occupies the over-deepened bedrock basin of an abandoned cirque.
Arête: A jagged, knife-edge, steep-sided bedrock ridge formed where two parallel alpine glaciers erode valleys on opposing sides of a mountain divide (derived from the French word for fishbone).
Horn: A steep, pyramid-shaped mountain peak formed where three or more cirque glaciers erode back into a central summit from opposing directions (e.g., the Matterhorn in the Swiss Alps).
Glacial Valley / Glacial Trough: A wide, steep-sided, flat-bottomed U-shaped valley carved by the advance of a valley glacier, contrasting with the narrow, V-shaped valleys cut by fluvial downcutting.
Hanging Valley: A tributary glacial valley whose floor sits perched high above the main glacial trough; created because the thicker trunk glacier eroded its bed far deeper than the thinner tributary glacier. The intersection often hosts high waterfalls.
Paternoster Lake: One of a stepped linear chain of small, interconnected glacial lakes filling bedrock basins along a glaciated valley floor, separated by vertical drops in elevation termed glacial steps.
Roche Moutonnée: An asymmetrical bedrock mound shaped by glacial transit; features a smooth, gently sloping stoss (upstream) side sculpted by glacial abrasion, and an irregular, steep, jagged lee (downstream) side plucked by freeze-thaw quarrying.
Fjord: A deep, narrow, steep-sided U-shaped coastal glacial valley that has been flooded by marine seawater. Formed during the Last Glacial Maximum when low eustatic sea levels allowed glaciers to scour bedrock below modern sea level; prominent in Alaska and Norway.
Sediment Characteristics: Glacial Drift versus Fluvial Sediment:
Glacial Drift: The collective term encompassing all sediments deposited directly by glacial ice or by glaciofluvial meltwater streams.
Glacial Till: Unstratified, unsorted sediment dropped directly by melting ice without fluvial reworking. Clasts range from large boulders to colloidal clays, chaotically jumbled together with no hydraulic size-sorting.
Fluvial Comparison: Fluvial sediment deposits are stratified and well-sorted by fluid dynamics; particle sizes transition downstream according to hydraulic velocity.
Glacial Erratic: A boulder of non-local lithology deposited by a melting glacier on foreign bedrock, often transported hundreds of miles from its bedrock source.
Morainic Landforms:
Lateral Moraine: A linear ridge of till deposited along the outer lateral margins of a valley glacier, built from mass wasting falling from adjacent valley walls and abrasion debris.
Medial Moraine: A dark ribbon of till running down the central axis of a valley glacier, created when the lateral moraines of two coalescing tributary valley glaciers merge.
Terminal Moraine: A prominent, curving ridge of unsorted till deposited across the snout of a glacier, marking the maximum down-valley extent of the glacier's advance.
Recessional Moraine: A distinct, transverse ridge of till deposited at the toe of a glacier where the ice margin stabilizes during a temporary halt in overall retreat.
Morphological Significance: Radiometric and cosmogenic dating of morainic sequences allows glaciologists to establish historical timelines of ice-age advance and calculate rates of retreat.
Glaciofluvial and Ice-Sheet Landforms:
Supraglacial Stream: A meltwater stream that flows across the open upper surface of a glacier.
Subglacial Stream: A meltwater stream that flows beneath the base of a glacier, transporting sediment under hydrostatic pressure.
Moulin: A vertical, cylindrical shaft or well bored through a glacier by surface meltwater plunging from the surface to the glacial interior and bed.
Outwash Plain (Sandur): A flat or gently sloping apron of glaciofluvial sediments deposited beyond the glacial terminus by sediment-choked braided meltwater streams; features sorted and stratified gravels and sands.
Proglacial Lake: A body of water ponded between the melting terminus of a glacier and an obstructing moraine or elevated bedrock barrier.
Drumlin: A streamlined, elongated, asymmetrical hill of till shaped by the passage of a continental ice sheet; exhibits a steep, blunt stoss end pointing up-glacier and a gently tapering lee end pointing in the direction of ice motion.
Esker: A long, narrow, sinuous ridge composed of sorted sand and gravel deposited within the subglacial channel of a meltwater river flowing beneath an ice sheet.
Kame-and-Kettle Topography: A hummocky glaciofluvial landscape characterized by chaotic mounds of sediment (kames) interspersed with closed depressions or lakes (kettle lakes):
A kame is a steep-sided mound of stratified drift deposited in a crevasse or meltwater delta along the ice margin.
A kettle lake forms when a detached block of stagnant, calving ice is buried within outwash sediment; upon melting, the overlying sediment collapses into a depression that fills with groundwater.