Gegn 101 Exam 2 Oceans/Shorelines/Floods/and Streams

Be able to reproduce the hydrologic cycle and the formula for

the hydrologic budget of a watershed

The continuous movement of water between the atmosphere, land, oceans, and groundwater through evaporation, transpiration, condensation, precipitation, infiltration, runoff, and groundwater flow.

Equation: P=Q+ET+DeltaS

P=percipitation

Q=Runoff/streamflow (leaving watershead)

ET=Evapotrasperation(evapration and plant transpriation)

Delta S= Change in water storage

What percent of the Earth's surface is covered by ocean, and

what percent of the total water on Earth is contained in the

oceans?

71% about is ocean 97% of water is ocean and 3% is fresh water

What percent of ocean water is dissolved salt?

3.5% of ocean water is dissolved salts

Which is most dense: a) salty or fresh water/ b) warm or cold water?

Salt water is more dense and colder the water is the denser it is

What is the chemical reaction when CO2 dissolves in water, and what happens if this chemistry reacts with Ca or Mg?

CO2->carbonic acid ->H+ and bicarbonate HCO3-

When it meets Ca or Mg it promotes dissolution forming calcite and dolomite so limestone

What two common gasses and one common mineral dissolve better in cold water?

O2 CO2 are the gases and Calcite CaO3

What drives surface currents, and what drives deep ocean

currents?

Surface currents are driven mainly by the wind but deep ocean currents are driven by thermohaline circulation which is differences in water density due to salinity and temperature.

What effect do these currents have on the heat distribution of the planet, and what would happen if these currents slowed down or were not as efficient at this process?

Ocean currents redistribute heat around Earth, moving warm water toward the poles and cold water toward the equator. If currents slow down, heat distribution becomes less efficient, potentially causing regional climate changes, including cooling in some regions and warming in others.

What causes tides? When do you get the highest and lowest amplitude tides, what are they called, and what astronomical configuration gives rise to each?

Cause: The gravitational pull of the Moon (primarily) and the Sun, combined with the effects of the Earth-Moon system's motion.

Highest-amplitude tides — Spring tides: Occur at new moon and full moon, when the Sun, Moon, and Earth are aligned.

Lowest-amplitude tides — Neap tides: Occur at first-quarter and third-quarter moons, when the Sun and Moon are at roughly 90° angles relative to Earth.

What effect do tides have on the Earth's rotation, and the Moon's revolution around and distance from the Earth?

Earth's rotation: Tidal friction gradually slows Earth's rotation, making days longer.

Moon's revolution: The Moon gradually moves farther away from Earth as it gains orbital energy, and its orbital period increases.

Earth slows down -> moon moves 3.8cm away

Know what factors affect the size and power of waves.

1. Wind speed — stronger winds produce larger waves.

2. Wind duration — winds blowing longer produce larger waves.

3. Fetch — the distance wind blows across open water; longer fetch produces larger waves.

On a picture showing a series of waves, be able to label the following features: crest, trough, wavelength (L), wave base.

Crest: peak

Trough: dip

Wavelength: distance between crests

Wave Base: The depth below the surface where wave orbital motion becomes negligible; approximately half the wavelength for a typical deep-water wave.

Know what happens to a wave as it approaches a shoreline.

As a wave enters shallow water, it interacts with the seafloor. Its speed decreases, wavelength shortens, and wave height generally increases until the wave becomes unstable and breaks. This is called wave shoaling and breaking.

What is the difference between a primary and secondary coastline?

Primary coastline: Shaped mainly by nonmarine processes, such as river deposition, glaciers, volcanic activity, or changes in sea level. (not boundry)

Secondary coastline: Shaped mainly by marine processes, such as wave erosion, tides, and coral reef growth. (plate boundry)

Understand the concept of wave refraction and its importance to coastal erosion.

Wave refraction is the bending of waves as they approach shore at an angle because different parts of the wave slow down at different rates in shallow water. It concentrates wave energy on headlands and spreads it out in bays, causing greater erosion of headlands and more deposition in bays.

Know the difference between longshore current and beach drift, and know if they go in the same or opposite directions.

Longshore current: Water flowing parallel to the shoreline, driven by waves approaching the beach at an angle.

Beach drift (longshore drift): Sediment transported along the beach by angled swash and backwash.

Direction: They generally move in the same direction along the coast.

How do humans attempt to control beach erosion?

Humans use hard stabilization structures and beach nourishment to reduce erosion:

Beach nourishment: Adding sand to replace eroded beach material.

Seawalls: Walls built along the shore to protect land and buildings.

Groins: Structures extending perpendicular to the shore that trap sediment moving along the beach.

Breakwaters: Offshore barriers that reduce wave energy.

Jetties: Structures built near inlets to stabilize navigation channels and trap sediment.

Between what two latitudes can hurricanes form?

between 5° and 20° latitude north and south of the equator.

What two factors compete against each other regarding hurricane formation in a warming world, and what prediction results from this?

1. Warmer ocean temperatures provide more energy and moisture, favoring stronger hurricanes.

2. Increasing wind shear can disrupt developing hurricanes, making formation more difficult.

Prediction: Hurricanes may become more intense and produce heavier rainfall, even if the total number of hurricanes formed does not increase and could potentially decrease.

Historically, what has been the main cause of damage when a hurricane hits shore, and is it getting better or worse?

Storm surge (katrina) it is getting worse as sea level rises

What are three ways to change global sea level, and which, if any, are we concerned about today?

1. Glacial ice growth or melting: More land ice melting raises sea level; more ice accumulating lowers it.

2. Thermal expansion or contraction: Warming seawater expands and raises sea level; cooling seawater contracts and lowers it.

3. Changes in the amount of water stored on land: More water stored in lakes, groundwater, and ice lowers sea level; water moving from land into the ocean raises it.

(SEA LEVEL RISE IS SCARY!!!)

What does the term "stream" mean to a geologist?

A stream is a body of flowing water that moves downhill through a channel, ranging from a small creek to a large river.

Know how the mouth, head, and base level of a stream are spatially related to the stream's longitudinal profile

-Head: High elevation, near the beginning of the stream.

-Mouth: Usually lower elevation, where the stream empties into a lake, ocean, or another stream.

-Base level: The lowest level a stream can erode down to; sea level is the ultimate base level for most streams.

-Longitudinal profile: A side-view graph of the stream's elevation from head to mouth. It is generally steep near the head and gentler near the mouth.

Know what will happen if the land a stream runs through should rise above (uplift), or fall below (subsidence) the longitudinal profile.

Uplift: The land rises above the stream's existing longitudinal profile, causing the stream to erode downward and form a deeper channel or valley.

Subsidence: The land sinks below the stream's existing profile, potentially causing the stream to deposit sediment as it adjusts to the new, lower landscape.

Why might a stream have to adjust to a new longitudinal

profile?

A stream adjusts to a new longitudinal profile when its base level changes, the land undergoes uplift or subsidence, or its water flow or sediment load changes.

Know the difference between a young, middle aged, and old aged stream.

Young — downcutting

Cuts deeply into the land, creating steep valleys.

Middle-aged — widening

Erodes sideways and begins forming meanders.

Old-aged — deposition

Flows across a broad, flat floodplain and deposits sediment.

Identify the following on a diagram: flood plain

Broad, flat area beside the river that floods periodically.

Identify the following on a diagram: cut bank

Steep, eroding outer bank of a meander.

Identify the following on a diagram: point bar

Gently sloping sediment deposit on the inner bank of a meander.

Identify the following on a diagram: oxbow lake

Crescent-shaped lake formed when a meander loop gets cut off from the main river

Identify the following on a diagram: meander scar

Crescent-shaped mark left behind by an abandoned river bend, often on the floodplain.

Identify the following on a diagram:yazoo stream/tributary

Smaller stream flowing parallel to the main river because natural levees prevent it from joining directly.

Identify the following on a diagram: terrace

Step-like, elevated flat surface along a river valley; an older floodplain left above the river's current level.

Identify the following on a diagram: levee

Raised ridge along the riverbank formed by sediment deposited during floods; can be natural or human-built.

Identify the following on a diagram: crevasse splay.

Fan-shaped sediment deposit formed when floodwater breaks through a natural levee and spreads across the floodplain.

Know the definitions of a watershed (drainage basin) and a drainage divide.

-Watershed (drainage basin): The area of land where all water drains into the same stream, river, lake, or other outlet.

-Drainage divide: The ridge or high ground that separates neighboring watersheds, directing water into different drainage basins.

What are the biggest drainage basin in the U.S. and the world?

Largest drainage basin in the U.S.: Mississippi River drainage basin.

Largest drainage basin in the world: Amazon River drainage basin in South America.

Know the difference between stream capacity and stream competence

Stream capacity: The maximum amount of sediment a stream can carry.

Stream competence: The largest sediment particle (by size) a stream can transport.

What form does a stream take on if its sediment load is greater than its capacity

A braided stream channel

Too much sediment for the stream to carry → sediment builds up → the stream divides into multiple channels

What is the name of the sediment feature created by a mountain stream that discharges onto a relatively flat plain?

alluvial fan

What is the name of the sediment feature created by a stream discharging into a larger body of water?

A delta like the Mississippi river delta

Know the definition of, and how to calculate, stream discharge.

volume of water flowing past a point in a stream per unit of time

equation: Q=A*V

discharge(m^3/s)=cross section ares(m2)* average velocity

Know what a hydrograph is. Know what is plotted on the x-axis and what is plotted on the y-axis

A hydrograph is a graph showing how a stream's discharge changes over time

X-axis: Time (hours, days, etc.).

Y-axis: Stream discharge

Know the definition of stream stage, how it differs from gauge height, and what a graph relating stage to discharge is called.

-Stream stage: The height of the water surface in a stream relative to a chosen reference elevation.

-Gauge height: The water level measured relative to a fixed reference point on a stream gauge. It is a measured reading and may not equal the stream's actual depth.

-Stage-discharge curve (rating curve): A graph showing the relationship between stream stage and discharge.

Know what is meant by flood probability and flood recurrence interval, and be able to compute both given flood records

Flood probability: The chance that a flood of a given size or larger will occur in any given year.

Flood recurrence interval (return period): The average number of years between floods of a given size or larger. It does not mean floods happen on a fixed schedule.

T=N+1/m interval in years=number of years/rank of flood 1=largest

What are two main causes for streams to become flashy, and how do these affect the hydrologic budget?

Urbanization: Pavement, roads, and buildings reduce infiltration, so more water becomes surface runoff and reaches streams quickly.

Deforestation: Removing vegetation reduces interception and often reduces water uptake by plants, increasing runoff and allowing water to reach streams faster.

What is the name of the event that caused the third largest loss of life in the U.S.A., and what caused it?

Johnstown Flood of 1889

Heavy rain + dam failure → sudden, catastrophic flooding.

What causes some of the biggest floods we see in the geologic record?

Some of the largest floods in the geologic record are caused by the sudden release of enormous amounts of water, especially from glacial lakes when ice dams break or glaciers retreat.

Spring Tide

everything in stright line

neap tide

everything 90 angle