Comparative Sedimentology

What is a crevasse splay?

A sedimentary fluvial deposit when a stream breaks it's levees and deposits onto a floodplain

What are alluvial rivers? What other river category is there?

Those flowing across their own deposits. The other category is incised rivers, which flow within eroded valleys

Define allostratigraphy

subdivision of the stratigraphic record into mappable rock bodies on the bases of it's bounding discontinuities

Describe the graded river profile

A graded longitudinal profile of a river is the natural shape it assumes due to the dynamic balance between water and sediment - stepper at the source, flattening to a fraction of a degree at the mouth

Define a thalweg

A curve of deepest points along the channel

What is a chute channel?

A narrow channel cutting off a point bar from the bank

What is an oxbow lake?

A lake created by an abandoned meander

What are allogeneic processes? And autogenic?

For a given depositional system, allogeneic processes are those which act outside of the system and affect the stratigraphic sequence, whereas autogenic are the internal ones

What is a point bar?

It is a crescent-shaped depositional feature made of well sorted alluvial deposit accumulated at the inside bend of a river.

What is a microscopic heterogeneity in a fluvial deposit?

A porosity-permeability variation

What is a mesoscopic heterogeneity in a fluvial deposit?

Variation between bedding units and sedimentary structures

What is a macroscopic heterogeneity in a fluvial deposit?

Variability associated with the deposition of channels and bars

What is a megascopic heterogeneity in a fluvial deposit?

Variations across major sedimentary units and entire basins

Why do rivers meander?

Because of turbulence, internal shear forces and bank-bed friction

How is a bottom of a straight channel shaped and why

There is a sinuous thalweg with alternate bars on the insides of it's bends, due to the same factors that cause point bars in meandering to rivers

What factors lead to a braided river?

Increased discharge, high discharge variations, higher slope, presence of coarse non-cohesive sediment which the river is unable to carry (may be brought suddenly due to a major flood or volcanic eruption)

How is sinuousity defined?

A ratio of the curvilinear and straight distance between two points

Which characteristics of single-thread and anastomosed rivers stand out in comparison with meandering and braided?

Low sinuousity, narrow channels (stable stream position), typically found on broad low-slope plains

Where do anastomosed rivers form?

In areas of rapid aggradation, such as confined, rapidly subsiding basins or where rapid base-level rise is matched by an abundant sediment supply.

How does bank vegetation influence channel evolution?

It stabilizes the bank, inhibits braiding and prevents flooding

How can a dam affect the river?

It reduces discharge variability, often leading to a development of a meandering style

How are mid-channel braid bars formed?

Outside of gentle bends in the thalweg, by a similar process as in point bar formation

What is the definition of a bedload?

Larger grains which are moved by sliding or rolling along the bed

How does a debris flow deposit look like?

Poorly sorted, contains large pebbles, cobbles or even boulders mixed together, embedded in a sand-silt-clay matrix. The matrix may show subtle grading, while the clasts may show a preferred orientation imposed by internal shear in the last flow moments

What is river competence and what does it depend on?

It is the maximum grain size that can be transported, depends on velocity and depth of the flow

What is river capacity and what does it depend on?

The total volume of sediment that can be moved, it depends on the magnitude of discharge

What is a crevasse of a river?

A break in the bank

What is pedogenesis?

Soil formation

What is the difference between a current ripple and wave ripple?

The former is asymmetrical (stepper on the lee side), the latter symmetrical

Characterize trough cross-stratification

In sections parallel to the flow we have curved planar erosional surfaces separating sets of foreset laminae. In perpendicular sections bowl-shaped trough surfaces separate concordant concave laminae. Formed by migration of ripples with irregular crests.

Characterize planar cross-stratification

In a section parallel to the flow we have flat erosional surfaces separating foreset laminae. In a perpendicular section laminae are flat and horizontal. Formed by migration of ripples with straight crests.

What is the difference between fluvial ripples and fluvial dunes/megaripples?

They are respectively smaller and larger than 5 cm in height. Dunes have larger wavelengths, may be covered by smaller ripples and they correspond to higher Froude numbers

What are upper flow regime bedforms and what stratigraphic record do they leave?

Froude number close to 1: upper plane bed, leaving horizontal laminae. Fr>1: antidunes, small upstream migrating bedforms that do not get preserved in the stratigraphic record

How to identify the growth of an active point bar?

Succession of vegetation - the oldest part will have trees, younger grass, youngest will be bare

What are floodplain deposits like?

Mainly fine grained clastic units

What is the process of avulsion?

Permanent diversion of a channel through a crevasse, if it has built up an alluvial ridge and the diversion results in a slope advantage for the channel

What is a perennial river?

A river which flows all year round

How do outcrops in ephemeral arid environment braidplains look like?

Tabular sandstone bodies several meters thick, consisting of plane-laminated sandstone. Or flood sheets comprising thinning and fining upward assemblages of cross-bedding and ripples

How could an outcrop of a braided river in an arid gravel-dominated environment look like?

Graded bedding of large grains due to size sorting during transportation. Or poorly sorted deposits from violent debris flows.

What depositional sequence is typical in alluvial settings and why?

Fining-upward. Aggradation of a channel results in decreasing flow depth and velocity, and consequently in a decrease in the competency and capacity of the flow. Development of point bars also tends to follow a fining-upward trend

What are thick sandstone sheets in alluvial settings like and what could they be attributed to?

4-16 m thick, possibly extending for many kilometers. They may reflect allogeneic causes such as gentle basin tilting or base level change

How does sediment deposit look like in ephemeral streams?

They are accumulated in flash floods, forming successions of stacked fining-upward sandstone sheets

What does a coarsening-upward sequence in proximal alluvial deposits indicate? How is it called and how big can it be?

It is a record of increasing source-area relief and depositional slope during tectonism (allogenic factor). It is referred to as tectonic cyclotherm and can be up to hundreds of meters thick and basin-wide

What is the concept of accommodation in stratigraphy?

The space available for sedimentation and how this volume changes in response to allogenic forces

What is an eustatic sea-level?

Distance from center of the Earth to the sea surface

What happens to the river when the base level drops?

If the exposed slope is steeper than river's graded profile, the river will erode its bed developing an incised valley. If the slope is more gentle, the river will increase sinuousity. If the river carries lots of sediment it may prograde and not incise.

What happens to a river valley during a stable sea-level period?

The valley will widen, which can be preserved in the form of terrace remnants along the valley walls

What does a sequence boundary represent in non-marine systems?

The final position of the subaerial erosion surface immediately prior to the commencement of a new phase of base-level rise

What happens to incised valleys during base-level rise?

They become estuaries

How does base-level rise affect alluvial deposition?

A decrease in slope in the lower course of the river leads to a reduction of competency and, consequently, in the grain size of the sediment transported and deposited

What is an alloformation sequence related to base-level changes?

FSST (falling-stage systems tract) -> SB (sequence boundary) -> LST (lowstand systems tract) -> TST (transgressive systems tract) -> MFS (maximum flooding surface) -> HST (highstand systems tract) -> SB

How is the maximum flooding surface reflected in stratigraphy?

Marine influence on typically fluvial deposits. Possible tidal influence (tidal bedding, reversing cross-bedding, sigmoidal bedding...)

Why is there no erosion surface within coastal fluvial systems which would correspond to lowstand erosion?

Because such surfaces are continually modified by channel scour, even during transgression

What happens to a channel during a transition from cold to warm phase? How about the other way?

Incision, because discharge increases while sediment yield is low. Rivers of anastomosing and meandering style tend to develop. The other way as well, except the discharge increase is not due to melting snow but reduced evapotranspiration.

Which river style develops in glacial and interglacial periods, respectively?

Glacial - braided. Interglacial - meandering

How are sedimentary rocks formed?

Weathering of source rock, transportation (water, wind, mudflow, glacier etc.), deposition and lithification (cementing, compacting), or direct precipitation (e g evaporites, reefs)

What is "detritus"?

Unconsolidated rock

How do mudstone-sandstone-carbonates proportions differ between the outcrop statistics and bulk chemistry of the Earth's crust? Why?

Mudstone constitutes ~50% of the outcrops but it should be ~80% based on crust chemistry based estimations (sandstones/carbonate make up the rest in ~3/2 ratio). Reason: mudstones may preferentially land on oceanic floors.

What are terrigenous clastic rocks?

Sedimentary rocks formed from clasts of particles (blocks/boulders/cobbles/pebbles/granules/sand/silt/clay) with a fragmental texture (discrete grains in tangential contact with each other)

What are rudites? What other categories are there?

Rudites are sedimentary rocks with gravel-sized (>~2 mm) grains. Other categories are arenite (sand grains) and lutite (clay grains)

What are the two main rudite types and what are their characteristics?

Breccias (angular clasts) and conglomerates (more rounded grains)

What is shale?

A fine-grained sedimentary rock characterized by fissibility, which is the tendency to break into thin slabs along it's laminations

Grain size categories

Above 256 mm: boulders, 64-256 mm: cobbles, 4-64 mm: pebbles, 2-4 mm: granules; 1/16 - 2 mm: sand, 1/256 - 1/16 mm: silt; below 1/256 mm: clay

Φ scale for grain sizes

Φ = -log_2(S), where S is grain size in millimeters

What is a measure of grain sorting?

Standard deviation of the grain size distribution

Which environments is well rounded and angular sand typical for, respectively?

Well rounded: eolian, nearshore (surf zone). Angular: glacial, turbidity currents

What is the difference between detrital and authigenic minerals? What are the examples of each category?

Detrital (quartz, feldspar) survive weathering and are transported in sediment grains. Authigenic (gypsum, halite) form in-situ in the depositional site in response to geochemical processes

Definition and examples of penecontemporaneous sedimentary structures

Created not during, but shortly after deposition. Examples: load casts, mud cracks

Definition and examples of primary sedimentary structures

Created during deposition. Examples: graded bedding, cross-bedding, wave ripples

What's the difference between strata and laminae?

Thickness, the boundary is usually set at 1 cm

What are sole markings and what processes are responsible for their formation?

Structures formed in the bottom of a bed by: 1) uneven weight distribution upon a softer (mud) layer (load casts), 2) current action reworking the mud surface, 3) activities of living organisms on that surface

Genesis-based subcategories of rudites

Epiclastic (physical disintegration or weathering of preexisting rocks), pyroclastic (explosive volcanic activity), cataclastic (local Earth movements or solution phenomena), meteoritic (extraterrestrial)

Volume % of sub-2 mm particles in conglomerates

Clast-supported: <15%, matrix-supported: 15-80%

What are orthoconglomerates and paraconglomerates?

Synonyms for clast-supported and matrix-supported conglomerates

How are conglomerates classified based on rock type composition?

Monomict - one type of rock, polymict - different types of rock

How does wind velocity change with height?

Increases logarithmically

What types of wind entrainment are there?

Reptation / creep (rolling, sliding along the ground) for largest grains, saltation for sand sized particles, suspension for dust (which can also be entrained secondarily by impact of salting sand grains)

What is friction velocity and how does it depend on grain size?

The minimal wind velocity needed to pick up (entrain) a particle. It has a minimum (~50-500 μm) - for small particles it's harder because of cohesion (~d^(-3)), for big harder because of gravity

Dune types and corresponding wind directions

Perpendicular: barchan - thin sides ahead, barchanoid - chain of barchans, transverse - barchans merged into undulating linear, parabolic - thick sides ahead, thin held by vegetation. Parallel: longitudinal (seif). Varied directions: star dunes

What is the difference between eolian ripple and dune?

Size threshold of 1 m

What are granule ripples?

Coarse grained ripples built on bedrock by reptation. Observed for example on Meridiani Planum

What are eolian dunes composed of (chemically)

On Earth: predominantly quartz, sometimes gypsum or basaltic in playa and volcanic environments, respectively. On Mars: basaltic, mafic composition

How are eolian dunes preserved in stratigraphic record?

Sandstones with cross-bedding at ~30° angle (angle of repose)

What are the dimensions of dust particles on Mars and Earth?

Mars: <1μm, Earth: <10μm

Why does Mars appear red?

Presence of iron oxides in basaltic dust grains

How are dust devils created?

Lifting of dust particles by a vortex of thermal flux from surface heating by the Sun. Usually form in the afternoon, when the surface has been sufficiently heated

Define loess

It is a thick deposit of wind-blown dust, forming an accumulation of loosely cemented clay, silt and sand, held together by cohesion. Often formed in periglacial settings (side edges of glaciers)

Define a ventifact

A rock modified by wind abrasion, typically with one flat side due to blasting sand

Define a yardang

Elongated hills with one (windward) side almost vertical. Sculpted by blasting of sand carried by a monodirectional wind, take thousands of years to form. Dimensions vary from centimeters to kilometers

Define a wind streak

A shallow, linear feature of different albedo due to deposition/erosion/protection from deposition near an obstacle in an environment with a prevalent wind direction

What are characteristics of distal depositional environments that set them apart from proximal?

Well sorted and well rounded sediment, rarity of large particles, transformation of feldspar to other minerals, less dependence on source area

When and why are buildings likely to collapse in earthquakes?

If they are standing on mud(stone), the mud becomes liquified (water entering pores) in the earthquake

Examples of laminar to turbulent flow transitions observed in real life

Water coming out from a tap or smoke coming out from a candle

Describe the Reynolds number concept

It is a ratio of inertial (d•v^2•l^2) and viscous forces (u•v•l), so Re=v•l•d/u, where v - velocity of the flow, l - flow cross-section, d - fluid density, u - fluid viscosity. Critical value of laminar-turbulent transition ain't fixed, but €[2000,3500]

Describe the Hjulström diagram

It defines areas in the parameter space of river flow velocity and grain size for which grains are: A) Deposited (threshold a bit above 0.01 mm, higher speed limits for bigger grains) B) transported, C) eroded (minimum speed at ~0.1 mm due to cohesion)

Define Froude number

A ratio of flow velocity v and a velocity of a contained wave √(g•l), where g is gravitational acceleration and l the flow depth. A value of 1 is considered to be critical

How does mud content affect debris on a slope?

As little as 5-10% can trigger a debris flow

What's the difference between a fluvial channel and fluvial valley?

Channel: the place where a river actively flows. Valley: depression formed by prolonged action of rivers (larger)

What's the key difference between braided and anastomosing channels?

Anastomosing channels do not migrate but keep the same location year after year

Cryosphere components

snowfields, valley glaciers, ice caps, ice sheets, floating ice (incl. icebergs), ice formed on lake surfaces, ground ice (permafrost)

Characterize a periglacial zone

An edge zone of a glacier where it is too dry or slightly too warm for the glacier to grow. Dominated by freeze-thaw cycles and deep-freezing of groundwater to form ground ice. Considerable potential for eolian processes to carry sediment such as loess

What is the difference between mountain glaciers and polar ice sheets in terms of sediment transportation?

The former move over bedrock, the latter over thick beds of soft sediment. Therefore, the ice sheets transport much more sediment

How is glacial ice formed?

Through repeated cycles of partial melting, referring and recrystallization. An intermediate stage between snow and ice, firn, has density greater than 0.5 g/cm^3. Final product of glacial ice reaches density of 0.9 g/cm^3 through further crystallization

How long does it take for glacial ice to form?

A few years in temperate areas. Hundreds of years in colder, dryer Antarctic areas

Describe the two zones of a glacier which are delineated by an equilibrium line

Accumulation zone: the mass of ice gained each year is greater than the mass lost by melting. Ablation zone: the other way around, at lower elevations and associated warmer temperatures.

What is and how to find out where is the equilibrium line of a glacier?

A location where there is neither gain nor loss of ice (averaged over ~1yr timescales). Can be approximated by the position of a snow line visible on a glacier at the end of the summer melt season.

Which factors besides gravity affect the downward creep ice movement along a glacier?

Thickness of the ice (increased shear stress) and temperature (ice close to the melting point can move faster (lower viscosity))

Where is most of the sedimentary record from Pleistocene glaciations preserved?

In submarine deposits

Where (in Alaska or Antarctica) do glaciers erode and transport more sediment and why?

In Alaska, because it's warmer and the temperature at the base of a glacier is close to the melting point at the pressure at the base. This also facilitates aggregation of refrozen ice debris that further boosts ability to erode

How is a roche moutonnée formed?

Abrasion of bedrock by a glacier on the stoss (upstream) side and plucking on the lee (downstream) side, resulting in a vertical wall on the lee side

Which various processes can lead to poorly sorted deposits?

Glaciers, landslides, pyroclastic flows, lahars, post-impact fallbacks

What is a lahar?

A volcanic mudflow, composed out of a slurry of pyroclastic material, rocky debris and water. Can be fast, deep and destructive

What is diamict?

Any poorly sorted deposit (matrix-supported conglomerate), regardless of origin

What is till?

A diamict formed by aggregation and direct deposition of debris transported by glacial ice

What kinds of till are there?

Melt-out (debris released from melting ice), lodgement (smearing debris from melting glacier base into bedrock) and deformation (shearing and mixing of preexisting sediment, most effective)

What is the most widely accepted theory about drumlin formation?

Either erosional streamlining of preexisting sediment or selective deposition of thick units of deformation till

What's the difference between drumlins and flutes?

Flutes are thinner and less likely to be preserved

How are eskers formed?

During ice retreat, when the subglacial channels where water used to flow rapidly become choked with sediment

What is the flow in glaciers like?

Laminar

How does the material in glaciers respond to deformation?

Upper layer is brittle, lower ductile

What is a cirque and what happens if multiple form close to each other?

A cirque is a concave amphitheater-shaped valley formed by glacial erosion. If two come next to each other, an arête (narrow ridge) is formed in between. If three or more converge, they meet at a horn (sharp peak)

Describe nunataks

They are isolated summits or ridges protruding out from glaciers, often forming pyramidal peaks

What is rock flour?

Debris pulverized to silt-sized particles generated by mechanical grinding of bedrock by a glacier. It can turn river's or lake's color grey, brown, turquoise or even milky white

What is an outwash plain?

An outwash plain, sometimes called a sandur, is a plain formed from glaciofluvial deposits due to meltwater outwash at a terminus of a glacier. These deposits are not cohesive, that's why formed rivers braid and not meander

How do current ripples move?

Saltation moves the sand grains in a current. As the flow passes the crest the grains move faster above the crest than behind (Bernoulli's principle, less z => more v). This creates a vortex of reverse flow depositing grains at lee side

How deep do wave ripples form?

Up to half the wavelength

What shapes a wave ripple?

Circular motion of water at a base of a wave

What are the characteristics of alluvial fans?

Conical fan shape, regular slope (on Earth 1°-5°) and presence of multiple diverging channels on the surface

What is a mudflow?

A debris flow dominated by fine grains

Why is there a distinction between debris flows and concentrated flows?

In the former, debris and water form a viscous slurry, which can be considered a one-phase fluid. In the latter, the water and solid particles are two different phases needed to be analyzed separately

What decides if current ripples have straight crests or not?

Curvy crests are due to lateral components of a vortex, occurring in higher flow turbulence

Describe the two types of lava

Pahoehoe: lower viscosity, smooth, coming in a slow, laminar flow. After it cools down one can walk on it. A'a': rough, pieces of rock, further from the volcano and lower temperature (~1170°C)

Walter's law of facies

If there is no unconformity, vertically successive facies correspond to adjacent depositional environments

Compare atmospheres on Mars, Venus and Titan

Mars: 0.0062 bar, -23°C, CO_2 dominated. Venus: 86 bar, 480°C, CO_2 dominated. Titan: 1.5 bar, -180°C, N_2 dominated

What is considered arid and semi-arid land?

The amount of yearly precipitation in millimeters should be below 10× the average temperature or 10-20× for arid and semi-arid respectively. Or UNESCO aridity index - ratio between precipitation and evaporation below 1/4 for arid land

What is desert varnish?

Thin exposed rock in arid environment

Define an inselberg

An isolated rock hill or mountain on a plain, formed by differential erosion

What is a bajada?

A series of coalescing alluvial fans coming out on the front of a mountain range

What is a pediment?

A very gently inclined erosional surface

Compare the ability of wind and water to entrain sediment

A water flow of 1 m/s has competence comparable to air flow of 30 m/s

Describe the division between ergs, sand sheets and regs

Ergs are areas with sandy dunes, which facilitate further accumulation of sand there. The remainder of a desert will be sand sheets (small ripples only) and regs (rocky desert pavement)

What is the grading in ripples in sand sheets and why?

Inverse grading because saltation is easier for coarser sand (less cohesion)

What kinds of alluvial fans are there?

Mass-flow dominated (debris flow) and stream-flow dominated (fluvial)

Coastal environment categories

Microtidal (tides under 2m), mesotidal (2-6 m), macrotidal (6-16m)

Tidal monthly cycles and related sedimentary record

Spring tide - full or new Moon, thicker sigmoidal layers. Neap tide - 90° Sun-Earth-Moon angle, smallest tides and thinnest sigmoidal layers

Describe the herringbone cross-stratification

Layers of foresets dipping in opposite direction, indicative of periodically changing flow directions in tidal areas. May be mistaken for 90° direction change without 3-dimensional information

Littoral zone subdivision

Supertidal - backshore (beach). Intertidal - foreshore (exposed at low tide, dominated by flat bed or antidunes). Subtidal: shoreface (where waves reach the base, including the surf zone), offshore (deeper, only deposits from major storms)

What's a berm in a coastal environment? How does berm formation depend on the season?

A sand or gravel ridge tens of centimeters high, formed by sediment brought by the bigger waves that got deposited above the normal sea level. Berms created in the winter are usually bigger than in the summer (stronger storm waves)

What is the most important coastal process at geologic time scales?

Sea level changes

How is transgression defined?

Sea moving inward on the land (usually due to sea level rise or land subsidence)

What is a chenier?

A long and high ridge made of sediments that were deposited as a strand plain (right at the coast) and then got preserved and moved landward through progradation

What's the difference between a marsh and a swamp?

A marsh has grass only, a swamp also trees such as mangroves

What happens to a barrier cutting off a lagoon when sea level rises?

It becomes submerged and either preserves it's shape or collapses to a drape. A new barrier and lagoon may form above

What mineral forms through diagenesis in nearshore deposits?

Glauconite (a type of phyllosilicate)

What is a strand plain and when is it formed?

Deposit building up at the shore, formed in wave-dominated environments (both transgressive and regressive)

When are estuaries formed?

In transgressive environments without excessive sediment supply. Can be both tide and wave dominated, in the latter case barrier island and lagoons may form.

How does an estuary/delta bring sediment to a basin?

If the inner sediment has higher density, it rolls down the basin floor. If the inner sediment has lower density than the outer one, it is suspended and then gradually drops.

What happens in coastal environments with very strong tidal power?

Tidal flats are formed instead of deltas or estuaries

How is the energy balance within an estuary?

Wave-dominated in the most seaward part, then more tidal energy and then more river energy

How are deltas different in polar environments?

They get reworked by sea ice pushing against them in the winter

What are listric faults in sedimentary rocks?

Faults which flatten as they get deeper, formed by creeping of the sediment, especially associated with tectonic compression or extension

Characterize climbing ripples

Formed by suspended sediment depositing on top of preexisting bedforms. Little to none stoss side erosion, consequently stoss side laminae can be seen. If there is deposition on the stoss side, they may take a sinusoidal shape

What's a flame structure?

Set of bowl-shaped laminations caused by the weight of overlying beds forcing the underlying beds to push through in water-saturated deposits

What is a piedmont glacier?

A large spread ice lobe associated with a terminus of a glacier. Glacial lakes can be formed after

What is hummocky cross-stratification and how is it formed?

Varying thickness of sandstone beds, formed by reworking by storms - above storm weather wave base but above fair weather wave base. If only concave indentations then it's called swaley cross-stratification

What is a playa and what other names are there?

A flat area with salt deposits, formed in a dried out lake (evaporation exceeded recharge), occasionally hosts some water (up to ~1 m after rain). Also known as sabkha, chott or salar

Are levees in a slope fan symmetrical?

No, because of the Coriolis effect

Evolution cycle of a delta

Progradation (river-dominated) => abandonment, transforming into wave-dominated system with barriers and lagoons => subsidence/transgression leads to drowning of the barrier into an inner shelf shoal => reoccupation

Main subareas in a delta

Delta plain (visible sediment plain), delta front (boundary between plain and slope), delta slope, prodelta (fully submerged)

What are hemipelagic sediments?

Terrigenous fine-grained sediments in deep-water settings

What are the conditions needed to form a Gilbert-type delta?

Transport of bedload as far as the river mouth, sufficiently low river/basin depth ratio, inertia-dominated effluent diffusion

Delta categories based on profile

Hjulström-type (low inclination, so called shoal water profile), Gilbert-type (angle of repose), mouth-bar-type (deposits forming bars that coalesce to build delta front)

Delta prototypes based on feeder system

A) very steep gradient, unconstrained flows, mass flows; B) steep gradient, unstable channels, bedload dominated; C) moderate gradient, stable channels, bedload dominated; D) low gradient, very stable, suspension dominated

Categories of deltas based on feeder and basin density

Hypopycnal, homopycnal, hyperpycnal

Evolutionary stages of alluvial fans

Precursor - steep talus -> rockfalls, rock slides, rock avalanches -> debris flows -> sheet flows & channelized flows

What is a coset?

A succession of several sets

Describe volcanic and plutonic rocks

Volcanic are extrusive, with microscopic crystals, categories segregated based on increasing silica content are basalt, andesite, rhyolite. Plutonic are intrusive and have coarse crystals, analogous categories are gabbro, diorite, granite

Types of volcanism

Subduction zone volcanism (mountain ranges), spreading center volcanism (rift), interplate volcanism (hot spots)

What is a toadstool in geology?

An undercut mushroom shaped rock pedestal attributed to wind erosion

What facilitates eolian dune formation?

Presence of local obstructions in the way of the wind