Geology

the maximum clast size transported

the total quantity of sediment carried

• Decrease in water velocity affects sediment transport
• Competence reduced, sediment drops out.
• Boulders, then gravels, then sands fill channel bottoms.
• Sands form inside banks (point bars).
• Silts and clays drape floodplains.

• Stream flow begins as scattered _______
• Water flow that occurs when the soil is infiltrated to full capacity and excess water from rain, meltwater, or other sources flows over the land.

• Evaporation
• Transpiration
• Precipitation
• Sublimation
• Infiltration
• Melting
• Runoff

• Branching or tree-like
• Common in regions of uniform material

• Draining in all directions away from a point
• Found at the perimeter of a high region or feature(mesa, peak, or mountain, etc.)

• Channels aligned primarily in two directions
• Common in gently sloped areas of orthogonally jointed rocks

• Trunk stream flows through resistant rocks,tributaries flow between ridges
• Common where surface alternates between erodible and resistant materials

• Several streams with parallel courses
• Common in surface with uniform slope

• Area of land that drains into a stream
• Land areas drain into a trunk stream or body of water

• The amount of water flowing in a channel
• Volume of water passing a point per unit of time
• Multiply cross-sectional area x average water velocity
• D = Ac x va

• The energy of flowing water is from mass and gravity
• Streams convert potential energy (PE) to kinetic energy(KE). KE (e.g., fast water flow) lifts and moves solids

the“sandblasting” of rock by particles in fast moving water

• Larger particles roll, slide, and bounce along the bottom
• Moves by saltation.

Fine particles (silt and clay) in the water

• Movement of solid particles
• High discharge—Large cobbles and boulders may move.
• Low discharge—Large clasts are not moved.

Change in elevation per distance flowed

The lowest point to which a stream can erode

• Velocity drops to zero when it reaches base level.
• Ultimate base level is sea level. 
• A lake is a local or temporary base level. 
• A ledge of resistant rock may define temporary base level

Stream flow slows, and the valley become filled with more sediment.

Stream flow quickens, and the incision of channels may leave stranded terraces.

• Gradient is so steep that water cascades or free falls.
• Scours a deep plunge pool.
• Basal erosion leads to collapse of overlying rocks.
• Temporary base levels.

• Trunk stream consists of many interfingering channels
• Sediment load is very high and channel is very shallow
• Abundant coarse sediment moves during floods.
• Sediment is deposited, chokes channel in normal flow.
• Weaving channels create ephemeral sand and gravel bars.

• The channel is modified during periods of flood
• Fast part of current swings back and forth
• Momentum increases during flood, erodes outside bank

• Forms when a stream enters standing water.
• Stream divides into a fan of distributaries.
• Velocity slows; sediment drops out.

• One stream captures the flow of another.
• A stream with vigorous headward erosion and steeper gradient intercepts a stream with gentler gradient.
• The captured stream flows into the new stream.

• Tectonic uplift may raise a region that has an entrenched stream.
• If erosion keeps pace with uplift, the stream remains in its channel.
• If the rate of uplift exceeds erosion by the stream, drainage changes.

A 100-year flood means 1% risk of such a flood in 1 year.

• Groundwater resides in subsurface pore spaces.
• Pores are open spaces within any sediment or rock.
• The total volume of open space.
• Geologic materials exhibit a wide range of porosities.

• Originally formed with the material.
• Voids in sediment
• Vesicles in basalt
• Open-reef framework

• Develops later
• Fracturing
• Faulting
• Dissolution

• The ease of water flow due to pore interconnectedness.
• Highly _____ material allows water to flow readily.

Sediment or rock that transmits water easily.

Impermeable or low permeability sediment or rock that hinders water flow.

• An aquifer that intersects the surface
• In contact with the atmosphere
• Easily contaminated

• An aquifer beneath an aquitard
• Isolated from the surface
• Less susceptible to pollution

Above the water table, pores are mostly filled with.

Below the water table, pores are filled with water

• Specific measurement of liquid pressure above a geodetic datum
• Measured by piezometer

Determined by measuring the hydraulic head. Flow always moves from a high to a low hydraulic head

Groundwater infiltrates through _____ areas

Groundwater exits the substance through ____ area.

An equation that predicts the volume of water passing through an area of an aquifer at any given time

Q = KA(h1 – h2)/j

• Q = Discharge volume (m3/day).
• K = Hydraulic conductivity (m/day).
• (h1 – h2)/j = Hydraulic gradient (m/m or dimensionless).
• A = Cross-sectional area perpendicular to flow (m2).

Natural groundwater outlets

• A downward-pointed conical-shaped surface
• Steepest near the well; flattens with distance 
• The cone may expand outward with continued pumping

• A small well creates a small cone.
• A large well creates a large cone.

• Water is heated to the boiling point in a vertical spring.
• Pressure exerted by the water column prevents boiling.
• Some water escapes and pressure is reduced.
• The water boils, turns to steam, and erupts as a geyser.
• The cycle repeats after the emptied chamber is refilled

• Water in pore space holds grains apart.
• When groundwater is removed:
• Sediment grains compress; pore spaces collapse.
• The land surface cracks and sinks.
• Irreversible

• Should effectively accept liquid wastes from your house and prevent biological and nutrient contaminants from getting into your well or nearby lakes and streams.
• Any, time these things do not happen, the system is failing.

• Expensive
• Most remedial strategies include removing the source.
• Pump and treat.
• Volatilize and vaporize.
• Steam clean.

Utilizes bacteria to clean groundwater

Develop when groundwater dissolves limestone

• Establishment of the water table in limestone
• Development of a cave network via dissolution (Dissolution maximized near the water table)

• Thick masses of recrystallized ice.
• Presently cover ~10% of Earth.

• Cold local climate (polar latitudes or high elevation).
• Snow must be abundant; more snow must fall than melts.
• Snow must not be removed by avalanches or wind.

Flow from high to low elevation in mountain settings

• Vast ice sheets covering large land areas.
• Ice flows outward from thickest part of sheet.
• Two major ice sheets remain on Earth: Greenland, Antarctica

• Significant quantities of meltwater forms at base of glacier.
• Water decreases friction, ice slides along substrate.

• Occurs below about 60 m depth.
• Grains of ice change shape slowly.
• New grains form while old grains disappear.
• Crevasses form at surface—upper zone too brittle to flow.

• Area of net snow addition.
• Colder temperatures prevent melting.
• Snow remains across the summer months.

Area of net ice loss.

• The leading edge of a glacier.
• Ice always flows downhill, even during retreat.

The glacial toe stays in the same place.

The glacial toe advances.

The glacial toe will retreat upslope.

• Bowl-shaped basins high on a mountain
• Form at the uppermost portion of a glacial valley.
• Freeze-thaw mass wasting chews into the cirque headwall.
• After ice melts, the cirque often becomes a tarn (lake).

• A “knife-edge” ridge.
• Formed by two cirques that have eroded toward oneanother

• A pointed mountain peak.
• Formed by three or morecirques that surround thepeak

• Glacial erosion creates a distinctive trough.
• Compare to V-shaped fluvial valleys.

• The intersection of a tributary glacier with a trunk glacier
• Trunk glacier incises deeper into bedrock.
• Troughs have different elevations.
• A waterfall results.

• U-shaped glacial troughs flooded by the sea.
• Accentuated by isostatic rebound.

Unsorted debris deposited by a glacier.

Forms along the flankof a valley glacier

Mid-ice moraine from merging of lateral moraines.

• Sediment dropped by glacial ice.
• Consists of all grain sizes—boulders to clay.

• Boulders dropped by glacial ice.
• These rocks are different from the underlying bedrock.
• Often, they have been carried long distances in ice.

• Sediments from an oceanic glacier
• Calving icebergs raft sediments away from the ice.
• Melting icebergs drop stones into bottom mud.

• Sediment transported by meltwater.
• Muds are removed.
• Sizes are graded and stratified.
• Grains are abraded and rounded.

• Wind-transported silt.
• Glaciers produce abundant amounts of fine sediment.
• Strong winds over ice blow the rock flour away.
• Deposits are unstratified and distinct in color.

• Long, aligned hills of molded lodgment till
• Asymmetric form—steep up-ice; tapered down-ice.
• Commonly occur as swarms aligned parallel to ice-flowdirection.