Environmental Geomorphology Study Guide Quiz 2michal76/classstudyguides/GEO 306 Environmental... · Wine Glass Canyon 1.) ... - ^Shattering – rocks with no preferred areas of weakness

Environmental Geomorphology Study Guide Quiz 2

Types of Faults Strike-Slip (Transverse) -“Right-Lateral” or “Left-Lateral”

-Cause ‘Off Set Streams’ -Example: San Andreas Fault, California

Normal Fault “Block Faulting” -“Fault Scarp” (on the Footwall), date surface -Rotational Down-Drops -Graben- german “grave”, down dropped area -Horst – up-faulted area

Reverse Fault

-Older rock on top of younger

“Overtrust Fault” -Keystone, Nevada


Basin & Range Province -Faulted Block Mountains (Nevada) -Bolson- a basin of interior drainage, water/sediement flows in and doesn’t leave! -One day the ranges will be buried in their own sediement. (Earth wants to be flat)

Alluvial Fans- fans that come out of valleys, edge of ranges, sediment dropped into valley. (in-filling of grabens & basins)

Bajada- colleased alluvial fans.

Playa- flat ‘salty’ areas, middle of basins, white/yellow (could be a lake)

Wine Glass Canyon

1.) Water spreads out on fan (Width increase, Depth decreases, *Velocity slows)

2.) Loss of water as it sinks into the coarse sediment. 3.) Lower gradient on fan facilitates deposition.


Steep Fans – some alluvium, some colluvium (gravity)

Talus – rock debris “fallen” from above. -Talus Cone – “falls” in… -Alluvial Cone – “washes” in…. Incision – related to ‘Stream Gradient’ & ‘Sediment Load’ -Water allows/wants to do as much work as it can, if it doesn’t Have sediment in load, it will pick it up! -Creates and Incision, then incised fans create a new alluvial fan.

Arroyo – boxed canyon -Western USA experienced more grazing; mid-1900’s = More runoff; Created ARROYOS… Ballenas – old, rounded Incised Fans.

Bajada – coalesced alluvial fans, large, expansive! -“Clastic Sediement” – sandstone, silt, pieces of rock.

ARROYO BALLENAS BAJADA

SALT PANS


Bornhardt- erosional relict -“Inselburg”, “Tor”, “Bornhardt” depends on where you are…

Playa – salty (every rock weathers; ions may produce salts, not washed away) -Salts not carried away to ocean (Bolson Here)…… “Precipitates”

Racetrack Playa (Death Valley) Rocks move on a flat Playa -Slick in rain events = rocks move

VOLCANISM Volcanism – movement of molten materials ‘beneath’ and ‘to the surface’. Magma- on surface Lava- below surface Pyroclastic Material – explosive event

“TEPHRA”: Physically blown material thrown from a volcano… “ASH”: < 2 mm (TUFF) “LAPILLI”: 2-64 mm (LAPILLISTONE) “BOMBS” : >64 mm, fluidal shape, blocks, angular tephra -twisted, air cooled masses, ejected

ASH LAPILLI BOMBS

Viscosity- resistance to flow, determines violence of the eruption. Determined by; -Amount of ‘SILICA’ : 13 orders of magnitude, More Silica = More Viscous -Amount of ‘ENTRAINED GASES’ : More Gases = More Viscous - ‘TEMPERATURE’ : lowered if water/lots of CO2 contained in melt


LAVAS Basaltic Lava (MAFIC, low silica) Highly fluid, low viscosity effusive (continuous outpourings from a vent/fissure) Silicic Lava (FELSIC, high silica) Highly viscous, explosive; often due to degassing at lower sfc pressures Continental locations

Laccolith – lake of rock (Stage B – Hogbacks created) LACCOLITH Evolution

Veins – small scale lava intrusions

Sill – flat, tabular, lava between strata layers

Dike – lava feature crosscutting strata Radiating Dikes – Shiprock, New Mexico


TYPES OF VOLCANOES

1.) CINDER CONES – Tephra 2.) SHIELD VOLCANOES – Mafic Lava 3.) COMPOSITE CONES – Felsic Lava / Tephra

Cinder Cones -Formed quickly (few days), Small, Steep-Sided, Soft Pyroclastic Material -Typically erupt from the side as debris accumulates around the cone -Crators of the Moon, IDAHO “Strombolian Eruption” – bubbles of gas expands & burst -Goes on for hours/days on end

Shield Volcanoes -Known as ‘LAVA DOMES’ -Mafic & Basaltic, Broad, Large -Mafic, Fluid lava, low angle (<3o Slopes), Very Large -Mauna Loa, Hawaii -Multiple fissures from which flow basaltic lavas (fluid) 2-50 m in thickness; up to 100’s of miles across -‘Hawaiian Eruption’ – lava fountains -‘Fire Pit’ on top -Mafic Lava – very viscous, fluid -Dependent on “Cooling/Flow Rates” +Aa (Crunch/Sharp), slow +Pahoehoe (Smooth/Ropelike), fast Lava Tube – lava flows through, river like, surrounding walls stay resistant

Aa LAVA FLOW PAHOEHOE LAVA FLOW LAVA TUBE

Lava Flow – extremely mafic, flat extensive -Flood Basalts- Pacific NW, flat extensive -May develop columnar jointing


Composite Cones

-Known as ‘STRATO-VOLCANOES’ -Big isolated volcanoes of the world, tall, explosive! -Tephra/’Silicic lava’ (flows poorly) in alternating layers, many dikes for strength. -One main vent, lava piles up (gets steeper), sticky, comes out cooler -Plugs main vent, pressures build up, erupts largely due to build up of gases. -World famous volcanoes (Cascade Range) -Erosion (tall, famous, to just a volcanic neck) -Devils Tower, Wyoming -Often have ‘CALDERAS’ -< 1 mile = Summit Crator ->1 mile = Caldera (Crater Lake, Oregon; Old Mount Mazama) -Mt. St. Helens Eruption = “Pelean Type”

Crater Lake, Oregon Devils Tower, Wyoming Mount St. Helens, Washington

Volcanic Hazards

1.) Poisonous Gases (CO2, CO, H2S) -Lake Nyos, Cameroon; 1986: CO2 gas killed everything within a 25 km. radius. -Usually a volcanic trigger

2.) Mudflows (Lahars) -Volcanic activity melts snowpacks, ‘meltwater’ mixed with ‘ash’ flows downslope. -Thick! Goes for miles! Wall of water, wipes out everything in its path. 3.) Fires – falling ash/lightening storms 4.) Structural Collapse of Buildings - 1 cm of ash on a roof = 2.5 tons! 5.) N’uee Ardente (glowing gas cloud) -‘Rapid’ debris, quick! Hot! Full of gas! -Pyroclastic Flow (rolling over itself) -Mt. Vesuvius, Italy (79 AD; buried Herculaneum & Pompeii)


Weathering – disintegration/decomposition of rocks ‘in place’. -end products are more in “equilibrium” with the surface environments physical & chemical conditions. Erosion – transport of material, typically downslope (sediments/soils) Denudation – weathering & erosion, landscape gets lowered. How are surface environments different than subsurface? Where rocks are formed (O2, Temperature, less Pressure, H2O, Biota present, Acid Rain, Human Influence Weathering susceptibility of a rock is a function of; -Minerals it contains -The Cementation of those grains together

-Cementation – affects ‘porosity’ & ‘permeability’, which affects water flow & flushing through the rock.

Weathering affects rocks from the edges in……… -Which is why we get ‘weathering rinds’ -Example: Weathering along joint planes, emphasizes that weathering Works on surfaces…. -End Result: “Spheroided Features” -“Spheroidal Weathering” – forms “TORS” (Joshua Tree NP)

Joshua Tree NP

Regolith – all unconsolidated materials ‘above bedrock’, regardless of origin. Residuum - weathered rock material ‘in place’ (NOT TRANSPORTED) Saprolite – weathered, rotten bedrock, still retaining some rock character/fabric.

Results of Weatheirng: Residuum -‘Plants/Biota’ turn Saprolite to Residuum -Also ‘water’ = loses of rock fabric. -Two general types of weathering processes; 1.) Physical Weathering – DISINTEGRATION 2.) Chemical Weathering – DECOMPOSITION

Physical Weathering -Rock broken into smaller pieces (creates more surface area) -along mineral grain boundaries (cementation) -grain by grain, or granular ‘disintegration’ (Granites/Sandstones) -material coming off rocks (Grus)


HOW DO ROCK BLOCKS BREAK-UP? -Grus – disintegrated granite rubble. - “Along Joint Planes” (Sandstones/Limestones/Basalt) - “Exfoliation” – sheets along curved joint planes (sheeting, miniature spalling/flaking) -Yoesmite NP (HALF DOME: best place in the world for exfoliation) - “Shattering” – rocks with no preferred areas of weakness (random shatter planes) Grus Joint Planes Exfoliation Shattering Processes of Physical Weathering Most Physical Weathering occurs because of Cold/Wet Places (ICE) or Hot/Dry Places (Crystals) Sets the stage for Chemical Weathering! (Physical Weathering)Rocks Sands Clays(Chemical Weathering)

1.) Unloading (Dilation) - Forms many of the initial joints

2.) Crystal Growth – forces open initial joint planes - Ice, salt, other minerals - “ICE” – increases in volume when it freezes (freeze/thaw)

o Best Places (High mountains, High latitudes, Near Continental Glaciers) Freeze, Thaw, Freeze, Thaw, Freeze, Thaw, ect. 50-80 miles – in front of continental glaciers

Felsenmeer – shattered/angular rock Need cool temperatures, but not so cold that freeze/thaw can’t happen

Water at top freezes first (insolating the bottom), under pressure offers lower freezing point. Ice also pushes out of the fracture at the top, not allowing total weathering potential.

Needle Ice – can lift soil at the surface (rising water vapor freezes, ‘frost heave’)

- “SALT” – 1.) Crystal Growth from salty liquid

Salt Water Dries Out Salt Crystal Growth/Formation 2.) Hydration (expansion) of crystals already in place 3.) Thermal Expansion (warmth of crystals is greater than for most rocks)

- Not just for Sodum Cloride (NaCl) o Limestone Gypsum (acid rain, creates gypsum crystals) o Physical Weathering is higher than chemical


- “Biotic Activity” – plant roots break up rocks - “Thermal Expansion” – creates new joint planes, mostly by lightening and fire - “Wetting/Drying” – creates new joint planes, wet = expands & dry = shrinks

Biotic Activity Thermal Expansion Wetting/Drying “Tafoni”

Chemical Weathering Q10 (increase temp. by 10oC) = 2 (Changes X 2)

1.) Warmth 2.) Water 3.)Surfaces

-Occurs on the surface… -Reaction byproducts ‘carried away’ by water… -Best reaction is H+ cations (acids) -‘Low PH’ is better than ‘high PH’ -Most Chemical Weathering occurs: Tropical Areas (humid, warm, wet, red soils) ---------------------------------------------------------

1.) Attacks (works on) mineral surfaces 2.) Reaction rate doubles as temperature increases by 10oC (Q10 = 2) 3.) Reaction byproducts must be carried away (in warm water) or reactions stop 4.) Lower PH conditions facilitate most forms of chemical weathering 5.) Results of Chemical Weathering: Clay minerals & Soluble ions (Red Clay)

-Most Chemical Weathering occurs at “B.”, holds moisture! -Most Physical Weathering occurs at “A.”, Bare Ground, Exposed! At “C.” the ground is covered with deep Regolith not allowing Physical Weathering processes to occur. No fresh water enters to allow for good Chemical Weathering.


Soils, Slopes, and Geomorphology

- Soils form from ‘Parent Material’ o Parent Materials accumulate during periods of ‘instability’.

Aggradation – new materials getting deposited Degradation – (erosion) new materials getting exposed

o Soils form during periods of ‘Stability’

Categories of Parent Material 1.)Residual – bedrock weathering in place -Rate of erosion < weathering rate, on long timescales -Primarily on stable, old land surfaces, humid climates ALL SLOPES ARE EITHER….. Transport-Limited – transport < weathering Weathering-Limited - weathering < transport 2.)Transported -By water = “ALLUVIUM” -By ice = “DRIFT” -By air = “SILT” (loess, sand) “PARNA” (dune sand, clay) -By gravity = “COLLUVIUM” 3.)Organic -peat (poorly decomposed), muck (highly decomposed), etc. - High water tables -Doesn’t allow total decomposition of materials SOIL MAPPING Soil Map Parent Material Map Soil Maps – detailed surfacial geology maps for glaciated areas. Residual = Soil maps look like bedrock maps… Where 2 different Parent Materials break = lithologicdiscontinuity WHY SO IMPORTANT? 1.)Persistance (Parent Materials stick around)…. 2.)Ability to help understand past Sedimentary processes…. +Step 1: Identify Parent Material +Step 2: Are there more than 1 Parent Material?


HOW TO IDENTIFY DISCONTINUITIES (Change in Sedimentation) 1.)Immobile function (content with depth) -‘Skeleton’ (framework, big stuff, coarse silts, gravel/sand) -Ratios are good, Stable, Stays in one spot -‘Plasma’ (fine silts, clays, small stuff) Unstable, moves 2.)Resistant (slowly-weatherable) minerals -Quartz, Potassium Feldspars, ZIRCON, TORMOLEAN -Ratio in depth, doesn’t always shoe discontinuity -Use ‘Skeletal’ & ‘Slowly Weatherable’ Soils The Soil Profile What happens to soils as they develop? (We can use in Geomorphology) 1.)Become more ‘anisotropic’ (develop horizons) -Not the same in all directions 2.)Become more weathered, especially in the upper profile -Best to use ratios: Resistant / Weatherable minerals (Zircon/Tourmaline) 3.)Get Redder Primary Minerals Secondary Minerals (clays)Layer Silicates(Brown in MI Kaolinite/Smectite) Oxide Clays (hematite/gibbsite) Iron Oxides/Aluminum Oxides -Reddness due to age or climate? (Most people believe *Climate*) 4.)Thicker Solum (everything above the C Horizon) 5.)Accumulate more materials in the B Horizon (subsoil)

Like surfaces, soils can over time do only 3 things; 1.)Develop (on stable surface ) 2.)Erode (on eroding surface) 3.)Get Buried (on aggrading surfaces) BURIED SOILS called ‘Paleosols’ or ‘Geosols’ (more formal)

Significance of Palesols 1.)Represent a ‘period of stability’ in the past. 2.)Provide ‘Paleoecological information’ 3.)Often’Can be Dated’(Radio-Carbon / Organic Matter) -Maximum limiting date on C14

-Helps determine the age of the overlying sediment (loess, Ap, wash in events = post sediment) -Established when soil formation Started -Established when the soil was Buried

3 TYPES OF PALESOLS 1.)BURIED 2.)RELICT - old but not buried 3.)EXHUMED – buried but material was removed


TRUNCATION – common during burial. Soil that has lost all or part of the upper soil horizon or horizons by soil removal, e.g., erosion or excavation CUMULIZATION – during and after burial. Bottom soils move up and incorporate in the above horizon (accumulates and thickens)

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Environmental Geomorphology Study Guide Quiz 2michal76/classstudyguides/GEO 306 Environmental... · Wine Glass Canyon 1.) ... - ^Shattering – rocks with no preferred areas of weakness