UIOWA SEES:1030 Final

Angle of Repose

the steepest angle at which loose material remains stable without sliding downhill

Controls on Angle of Repose

grain size, shape, sorting, moisture content, vegetation, and slope stability

Fall

free-falling rock

Slide

material moves as a block along a surface

Flow

material moves like a fluid downhill

Slump

rotational slide along a curved surface

Creep

very slow downslope movement of soil or regolith

Avalanche

rapid movement of snow, ice, or debris downslope

Permafrost

permanently frozen ground

Solifluction

slow flow of water-saturated soil over frozen ground

Turbidity Current

underwater flow of dense, sediment-laden water moving downslope

Graded Bed

sediment layer with coarse grains at bottom and finer grains upward

Deep-Sea Fan

fan-shaped deposit formed where turbidity currents exit submarine canyons

Alluvial Fan

fan-shaped deposit formed where a stream exits mountains onto flatter land

Cut-Bank

outside of a bend where river velocity is highest and erosion occurs

Point Bar

inside of a bend where river velocity is lowest and deposition occurs

Base Level

the lowest level to which a stream can erode its channel, usually sea level

Young River

fairly straight and flows in a narrow V-shaped valley

Intermediate-Aged River

begins to meander and develop a flood plain

Mature River

meandering river that wanders within a well-developed floodplain

Distribution of Freshwater

most freshwater is stored in glaciers/ice caps and groundwater, with only a small amount in lakes and rivers

Aquifer

rock or sediment that stores and transmits groundwater

Aquitard

layer that restricts groundwater flow

Gaining Stream

stream that receives groundwater input

Losing Stream

stream that loses water to the groundwater system

Perched Water Table

localized saturated zone above the main water table caused by an impermeable layer

Hydraulic Gradient

slope of the water table that drives groundwater flow from high head to low head

Cone of Depression

localized lowering of the water table in the pumping area

Drawdown

lowering of the whole water table

Waves

periodic undulation of the ocean surface driven by wind

Swash

landward motion of water as waves break onshore

Backwash

oceanward motion of water back down the beach

Longshore Current

flow of water parallel to the coast because waves are not exactly parallel to the shoreline

Accretionary Coast

shoreline builds outward from sediment supply

Erosional Coast

sediment is removed faster than it is supplied

Types of Deserts

subtropical deserts, rain-shadow deserts, continental interior deserts, and coastal deserts

Playa

dry lake bed where water temporarily collects and evaporates

Desert Landforms

dunes, playas, alluvial fans, mesas, buttes, arches, and canyons

Rain Shadows

dry conditions on leeward side of mountains after moist air loses precipitation on windward side

Effects of Wind in Deserts

erosion by deflation and abrasion, transport of sand, and dune formation

Accumulation

snowfall adds to the volume of glacial ice

Ablation

melting, sublimation, and calving subtract from the volume of glacial ice

Kame

hill of stratified drift deposited by meltwater

Esker

sediment deposited in meltwater tunnels beneath a glacier

Drumlin

hill of till shaped by glacier overriding it

Kettle

depression formed when a till-covered ice block melts

Moraine

pile of sediment carried on or left behind by a glacier

Continental Glacier

vast ice sheet that covers large parts of a continent, spreads outward in all directions, and is not confined by topography

Alpine Glacier

glacier that forms in mountains, flows downhill through valleys, and is confined by surrounding ridges and slopes

Silicates

the most common mineral group in Earth’s crust, made of silicon and oxygen combined with other elements

Dark Silicates

silicate minerals rich in iron and magnesium, giving them a dark green, black, or brown color and making them denser EX: olivine, pyroxene, amphibole, biotite

Light Silicates

silicate minerals low in iron and magnesium and richer in aluminum, potassium, sodium, or calcium, giving them a lighter color EX: quartz, muscovite, feldspar

Bowen’s Reaction Series

first to crystallize from cooling magma is olivine (dark) at highest temperatures, while last to crystallize is quartz (light) at lowest temperatures

Aphanitic Texture

small crystals produced from rapid cooling

Phaneritic Texture

large crystals produced from slow cooling

Porphyritic Texture

tells you that the rock cooled at two different rates and times

Pegmatitic Texture

extremely coarse-grained

Principle of Superposition (Geologic Principle)

What ever is on top is younger than what's on bottom.

Principle of Original Horizontality (Geologic Principle)

Beds are originally deposited parallel to the horizon (i.e. horizontal)

Principle of Lateral Continuity (Geologic Principle)

Beds are deposited uniformly in lateral directions unless something is blocking them.

Principle of Cross Cutting Relationships (Geologic Principle)

Whatever is doing the cutting is younger than what gets cut.

Shield Volcano

are huge, shallow, and exclusively basaltic composition; lower silca compositions (Hawaii)

Composite Cone Volcano

are mountain sized and typically intermediate composition; have alternating layers of lava and ash (Mt. St. Helens)

Cinder Cone Volcano

are tiny and form from gaseous magmas (Sunset Crater)

Protolith

The original rock from which a metamorphic rock forms. AKA the "parent rock"

Strike-Slip Fault

Type of fault where the movement is mainly horizontal. Caused by shear stress. E.g., San Andreas Fault

Dip-Slip Fault

Type of fault where the movement is mainly up and down. Includes normal and reverse faults.

Elastic Deformation

Temporary change, returns to original shape. Think of a rubber band bending.

Plastic Deformation

Permanent bending without breaking. Like bending clay.

Ductile Deformation

Low, permanent bending/stretching (deep underground). Similar to plastic deformation. ***FOLDING

Brittle Deformation

Rock breaks or fractures. Happens near the surface where it is cooler. ***FAULTS

Normal Fault

Caused by tension → hanging wall moves down

Reverse Fault

Caused by compression → hanging wall moves up

Thrust Fault

A low angle (less than ~45°) reverse fault. Common in mountain building.

Transform Fault

Rocks slide past each other horizontally due to shear stress. AKA Strike-slip

Anticline

Rock layers fold upward into an arch shape. Oldest rocks in the center. Looks like an upside-down U (∩)

Syncline

Rock layers fold downward (bowl shape). Youngest rocks in the center. Looks like a Smile U shape (∪)

Fault-block Mountains

Formed by Tension faults; blocks tilt or drop. Example: Sierra Nevada

Volcanic Mountains

Formed by magma erupting and building up layers. Example: Mount Fuji

Dome Mountains

Formed by uplift of rock layers (usually magma pushes up but doesn't erupt). Example: Black Hills

Regolith

The layer of loose, unconsolidated material that sits on top of bedrock; rock and mineral fragments

Humus

The nutrient-rich, decomposed organic matter in soil.

Soil Horizons (Layers)

- O horizon: Topsoil - Loose and partly decayed organic matter

- A horizon: Topsoil - Mineral matter mixed with some humus

- E horizon: Light colored mineral particles; Zone of leaching

- B horizon: Subsoil - Accumulation of clay from above

- C horizon: Subsoil - Partially altered parent material

Isotopes

Atoms containing a nucleus with varying #'s of neutrons.