Geography 2051 Exam 2 - Namikas (LSU)

Weathering

the breakdown of earth materials into smaller components

Physical Weathering

involves physical forces (pushing/pulling) breaking down earth materials

Chemical Weathering

the process that breaks down rock through molecular changes using water

Parent Material

The original rock or soil type

Regolith

the substance that parent materials of rocks break down into before turning into soil

Soil

the result of weathering of rock from parent material to regolith then to this substance

What are some factors/controls of weathering?

*LOOK AT NOTES*

-Nature of Parent Materials/Rocks

-Climate (moisture levels & temperatures)

-Hydrology

-Topography

-Vegetation

Jointing & it's effects on rocks

joints are cracks in rocks; they affect the solubility and rate of weathering in/on rocks

Moh's Hardness Scale

A scale ranking ten minerals from softest to hardest; used in testing the hardness of minerals

How does climate affect weathering?

Precipitation influences how strong/weak weathering is, as well as rates

& temperature influences which type of weathering occurs

What type of weathering occurs in hot climates?

Chemical weathering

What type of weathering occurs in cold climates?

Physical weathering

Hydrology

the study of movement of water

How does hydrology affect weathering?

It influences the rates & strength of weathering

(more exposed to water=higher rate of weathering)

Topography

the shape and physical character of Earth's surface

Microclimate

very small areas in which topography and hydrology affect vegetation and water movement (which in turn affects weathering)

Vegetation such as root wedge/root pry _____ weathering

enhance

Vegetation such as biological controls ____ weathering

inhibit

Most physical weathering processes result in...

jagged pieces

Most chemical weathering processes result in...

rounded pieces

What are some types of physical weathering processes?

-frost action/freeze-thaw

-root wedging

-crystallization

-pressure-release (exfoliation/spalling)

Root Wedging

a physical weathering process in which plant roots break rocks apart

Crystallization (aka salt wedging)

a physical weathering process in which salt crystals grow in pore spaces on a rock's surface and dislodge individual mineral grains within the rock

Pressure-Release (Exfoliation/Spalling)

the tremendous pressure rocks are exposed to at the surface causes them to break

Frost Action (aka Freeze-Thaw)

water that's between cracks in rocks freezes and thaws & causes the rock to shatter

What are some examples of chemical weathering processes?

-oxidation

-hydrolysis

-carbonation

-solution

Oxidation

commonly known as "rusting"; oxides in rock formations cause weakness and allow rocks to break down

Hydrolysis

the chemical breakdown of a compound due to reaction with water (water breaks down feldspar in granite)

Carbonation

process by which minerals reacts with carbonic acid; effective in attacking limestones

Solution

a mixture that forms when one substance dissolves another (carbonation is an example)

Karst Topography

a region in which a layer of limestone close to the surface creates deep valleys, caverns and sinkholes.

Limestone

a sedimentary rock consisting mainly of calcium that was deposited by the remains of marine animals

Tower Karst

large, rounded outcrops of limestone (aka Haystack Karst)

Pinnacle Karst

pinnacle-like remnants of an eroding limestone surface produced by accelerated carbonation in the humid tropics (very rugged terrain)

Sinkholes

a depression in earth's surface that results from the weathering of carbonate rock underground

Collapse (sinkholes)

surface material collapses into a cavern (empty areas below the ground)

Karst Valleys

short and small valleys that appear as stream valleys without streams; numerous sinkholes converging together

Disappearing Streams

streams that flow into a sinkhole and disappear

Caves/Caverns are both ___ and ___ in nature

erosional & depositional

Erosional Cavern

the empty space below earth's surface was originally limestone, but eroded over time

Depositional Cavern

created after the empty space below earth's surface emptied out

Dripstone

result of water dripping into caverns & depositing sediments

Stalactites

water dripping from above & results in deposits hanging down from the ceiling

Stalagmites

buildups of limestone deposits on the ground (build upwards from the ground)

Column

huge limestone deposits (stalagmites)

What are more examples of dripstones?

soda straws and drip curtains

Slope

a curve or incline surface that represents the boundary of a land created from weathered material

What's important in knowing how to deal with slopes?

Stability

How are slopes considered systems?

What are the inputs? Outputs?

Inputs: materials that have weathered out of the surface and tumbled down & becomes part of the slope

Outputs: materials that are carried out into the water

Angle of repose

the steepest angle that a slope can maintain without materials falling further (equilibrium)

What forces affect slope stability? (these cause angle of repose)

-driving forces (gravity & water)

-resisting forces (friction & cohesion)

What are the slope elements?

-waxing slope

-free face/fall face

-waning slope

-debris slope

Waxing Slope

portion of top of slope where angle of the slope is increasing (steepness increases); convex surface

Free Face/ Fall Face

steepest portion of slope

Waning Slope

portion of slope that angle is decreasing (steepness decreases); concave surface)

Debris Slope

zone of material accumulation

Mass Movement

movement of land that causes materials on slopes to move and change landscapes

What characteristics are used to classify mass movement?

Speed, water, and materials involved

What are the 4 major types of mass movement?

Rockfall/Avalanche, (Debris) Flows, Slides, Creep

Rockfall/Avalanche

fastest type of movement; Earth materials that move lose contact with slope completely & gain speed (water can cause these, but it'snot needed)

(Debris) Flows

Rapid (but not as fast as rockfall); Earth materials have some contact with the ground, which causes friction & speed to decrease (LOTS of water is needed)

Slides

Materials detach and move as a cohesive unit down the slope; huge amounts of friction; intermediate speed

Creep

Slowest type of mass movement; extreme friction; gravity causes the materials to slowly shift and move down the slope

Controls (slopes)

characteristics that influence how slopes change and develop over time

What are the controls of slope development?

rock strength, climate, and process balance

Weathering Limited

material is transported away as fast as it's being weathered; production rate is slower than transport rate

Transport Limited

weathering of materials is faster than carrying out of weathered materials

Slope Decline Theory

slopes get flatter over time; entropy occurs (things become less organized over time)

Parallel Retreat Theory

materials weather out and move parallel to themselves

Slope Replacement Theory

transport limited; cliff faces weather but materials pile up & replace a sheer slope with a debris slope

How much (%) of Earth;s surface does water cover?

70%

True or False: We are experiencing water shortages and quality of water is decreasing.

True

True or False: Water dams provide water to over 40 million people.

True

What's the global distribution of water on Earth's surface?

97% Ocean & 3% Freshwater

What's the breakdown of freshwater on earth's surface?

20% is groundwater

80% is on the surface

What's the breakdown of freshwater that's on the surface?

More than 99% of surface freshwater is in the form of ice; less than 1% is in the form of rivers, lakes, reservoirs, etc.

Hydrologic Cycle

the movement of water through larger earth systems & is driven by solar energy is an exogenic process

What are the four components of the hyrdologic cycle?

-changes in state

-movement/pathways

-reservoirs

-global balance/budget

Changes in state

changing from solid to liquid to gas (water is the only substance that can be all three states)

Evaporation

change in state of water from liquid to gas

Condensation

change in state of water from gas to liquid

Sublimation

the direct transition from a solid to a gas form & also the reverse transformation from a gas to solid form

movement/pathways

-vertical processes move water up and down (lifting & precipitation)

-horizontal processes move water horizontally (runoff & groundwater flow)

Global Budget/Balance

the amount of water on earth's surface is considered to be constant

Reservoirs

store water

residence time

the average amount of time that water spends in a particular reservoir (these are dependent on how large the reservoir is)

advection

horizontal transport of gases; this process helps maintain the balance of water in ocean & nearby land atmospheres

groundwater

very important water resource (about 1/5 of water in the US)

Aquifer

large bodies of porous rock/materials that store water (unconsolidated material)

Saturated Zone

the areas in an aquifer in which all pores & fractures are saturated with water (below the water table)

Water Table

portion of aquifer in which all surfaces are permanently saturated by water

Zone of Aeration

portion of water table not filled with water; at top of water table

Aquiclude

body of impermeable/nonporous material that won't allow water to penetrate

Recharge Rate

how fast groundwater systems refill with water

Confined Aquifer

partially covered by an aquiclude and don't allow very much inputs of water; slower recharge rates

Unconfined Aquifer

area above the system is fully open and can receive inputs of water; faster recharge rates

Groundwater as a system (what are inputs & outputs)

Inputs: precipitation

Outputs: natural & human processes (wells)

Groundwater Mining

the process of extracting water where there is little to no groundwater recharge

Cone of Depression

cone-shaped depression surrounding wells and other human-made uses of groundwater (b/c aquifers can't resupply water as fast as people pump it out)

Saltwater Intrusion

an infiltration of salt water in an area where groundwater pressure has been reduced from extensive drilling of wells (sea water has opportunity to push freshwater further inland)