MEA 250 Notes

Waves- causing erosion and deposition

The nearshore and shore

Foreshore and backshore

The area from the coastline to the high-tide shoreline

Well developed cliffs, tectonic activity, headlands, wave-cut cliffs with sea caves

Beach, spit, bay barrier, barrier islands, deltas

Steep, rugged shorelines and narrow continental shelf, active continental margin(tectonic activity)

Gently sloping shorelines, wide continental shelf, passive continental margin(no tectonic activity)

Similar to Atlantic Coast, but smaller wave size and tidal range. Dominant feature is Mississippi River Delta

Extension of rock placed perpendicular to the beach to trap sand from longshore drift

They usually make erosion worse on the down-drift side of the groin

Built to protect coastal cliffs and bluffs(the entire slope between a marine terrace or upland area and the sea) from eroding

They end up eroding the beach by reflecting wave energy back onto the beach

Offshore sand is often finer (made up of smaller particles), so it erodes away within a short period of time

Crust, lithosphere, asthenosphere, mesosphere, outer core, inner core

In order from outer to inner: Lithosphere, asthenosphere, mesosphere

Thicker than the crust, described as rigid. Includes crust and upper portion of mantle

Described as plastic (can be depressed or molded)

Iron (Fe) and Nickel (Ni)

Where two plates separate. Example: mid-atlantic ridge

Where two plates overlap. Example: Pacific ring of fire, Western Andes mountains in South America

Where two plates slide against each other. Example: San Andreas Fault

At ridges where plates diverge. Oldest ocean is the farthest from the ridges

Passive margin is where there is no subduction or convergent plate boundary. Active margin is where two plates meet and subduction occurs

South and East Asia contribute ~70% of sediment to the ocean. This is due to tectonic activity and human activity in this area

The solid material that is transported by a natural agent, especially a stream or the mass of sediment passing through a stream cross section in a specified period of time, expressed in millions of tons.

Sediment load per unit of drainage area. Total sediment discharge from a watershed relative to the watershed area, expressed in units of mass per unit time per unit area.

Take the total sediment load divided by the total area

Greater rainfall/runoff, larger basin size (and larger basin size also causes decreased sediment yield, because yield is a function of total basin area)

Distance from crest to crest

Distance from trough to crest

Number of waves that pass a certain point in a period of time

Waves that occur where the water depth is >1/2 the wavelength

Waves that occur where the water depth is <1/2 the wavelength

When their height to wavelength ratios are 1/7 or more

Wind speed, wind duration, and fetch(distance traveled)

= (gd)^1/2 where g is the gravity constant and d is water depth

Orbital motion- Circular motion of water as wave movement passes through

Whenever waves approach the shore and enter shallow water

On headlands and cliffs

The process by which wave energy spreads perpendicularly to the dominant direction of wave propagation

Wavelength: 100 km. Wave height: 1 m

The movement of material along a coast by waves which approach at an angle to the shore but recede directly away from it.

A relatively strong, narrow current flowing outward from the beach. Caused by convergence of longshore currents and wave set up.

Welded barriers, barrier spits, and barrier islands

Long, narrow, few inlets, wave-dominated, overwash common

Short and well developed, tide-dominated

Barrier is moving forward(away from the land), or ‘prograding’, over time. Occurs when there is abundant sediment supply.

Barrier is moving back(towards the land), or ‘retrograding’, over time. Occurs when the supply of sand is inadequate.

When sand builds upward due to rising sea level

Overwash is when storm-induced waves exceed the height of the dune, sand is transported over top of the dune and deposited inland. The two shapes that can form are a washover fan and a washover apron.

A long, narrow structure that intends to keep sand from flowing into a channel; intended to protect an inlet.

After a wave breaks, sediment moves toward the land

Sediment moving away from the shore

Light waves with low energy, long wave periods, sand is transported shoreward and piles up on berm

High energy waves, flatter and rockier beach, sand is stored as sandbar which will be swashed shoreward in summer

Wave refraction causes water and sand to move parallel to shore

The balance between erosion and deposition, and the angle of wave approach

Saltation, suspension, creep

Elongated, asymmetrical dune. Form at a right-angle to the wind

Have a single isolated dune lobe formed downward from a blowout

Horn shaped dune pointing downwind. No vegetation

Vegetation covered horn-shaped dune pointing upwind

The downward side of a dune that has a steep angle of 30-34^o. It faces away from the direction the wind comes from

Coastal plain, fjords, bar-built, tectonic

These estuaries were formed at the end of the last ice age when rising seawater flooded (or "drowned") existing river valleys. Example: The Chesapeake Bay

Glaciated, U-shaped valleys with steep walls. Example: Common Norwegian and Canadian coasts

These most commonly are barrier islands that are separated from land by a shallow lagoon. They are formed by the creation of sand bars parallel with the shore, usually adjacent to slow flowing rivers that discharge freshwater into the coastal waters. Wave action plays a pivotal roll in the creation of these sand bars. Example: Outer banks, NC

These are caused by earthquakes, where folding or faulting may create bays with narrow inlets to the sea. Example: San Francisco Bay

Wind-driven, tidal mixing, estuarine circulation(salt water goes under freshwater and pushes it out away from land when salt water rises)

Salt-wedge, partially mixed, well-mixed

The zone of highest turbidity resulting from turbulent resuspension of sediment. ETM is an important nursery area as many organisms use transport and retention within ETM.

Strong tidal forces, large density difference between river and ocean, long and narrow. Estuaries can be classified based on topogrophy or physics

Scientific Definition: A process by which a body of water progresses from its origin to its extinction. This process happens in stages(image). When lakes, streams and estuaries are over fertilized, excessive production of aquatic organic matter can become a water quality problem and as a result the eutrophication process can be enhanced.

This measures the rate of oxygen consumption by a sample of water, and therefore gives a good indication of eutrophication. A high BOD means lots of organic material and aerobic microbes, i.e. eutrophication.

Shallow water bodies separated from the ocean by a barrier, connected at least intermittently to the ocean by one or more restricted inlets, and usually oriented shore-parallel

Lagoons have little or no interchange with the open ocean or with fresh water and high evaporation rates

180 ppm and 280 ppm

2013

A coastal accumulation of riverborne sediment extending both above and below sea-level close to a river mouth. Examples: Mississippi River Basin, Amazon River Basin, Mackenzie River Basin

Smaller river, absence of large drainage systems preventing it from generating the amount of sediment needed. Also located on narrow and steep margins, meaning there is no proper site for sediment accumulation

From landward to seaward: Delta plain, delta front, prodelta

High water and sediment discharge, with small waves and low tidal ranges. A broad gently sloping continental shelf

Strong tidal currents, without substantial wave climate and strong river influence

Don’t really look like a delta, relatively small, and depends on longshore current patterns

The vertical rise and fall of the surface of a body of water caused primarily by the differences in gravitational attraction of the moon, and to a lesser extent of the sun, upon different parts of the earth

M is the mass of the Sun, m is the mass of a planet (i.e., Earth), and r is the distance between them.

Centrifugal force causes water to be bulge away from the center of mass of the earth-moon system when the earth-moon system rotates. These two forces(centrifugal+gravitational) combined cause the bottom photo, a bulge of water on both sides of earth.

Moon’s period: 27.3 days. Every 24 hour, Moon has traveled 13.2^o.

• After 24 hours, the moon has moved so the same spot on the earth would not be facing the moon exactly. This is why high tide in the same location occurs 50 minutes later each day, because it takes 50 minutes for the earth to rotate and catch up with the 13.2^o that the moon has moved from its initial position at the beginning of the 24 hours

Two tidal cycles daily with a period 12 hours 25 minutes. Common in majority of the world.

One tidal cycle daily, with a single high and low tide, period: 24hrs, 50min

during a lunar cycle: a small semi-diurnal inequality and a very pronounced one

They occur twice a month and are when the moon is between the Sun and Earth or is behind the Earth. Tides at these times are abnormally high and unusually low.

When the moon is located at right angles to the Earth-Sun line, occurs twice a month. At these times, high tides are lower and low tides are higher than usual.

An amphidromic point is a point within a tidal system where the tidal range is almost zero, and around which the tidal crest rotates through one tidal cycle.

An accumulation of sand on the seaward side of an inlet formed by the ebb tidal current

An accumulation of sand on the shoreward side of an inlet

The total volume of water moving past a fixed cross section of the estuary during each flood tide or ebb tide is referred to as the tidal prism. The larger the tidal range within the estuary and the greater the dimensions of the estuary, the larger the tidal prism. On average, the ebb and flood tidal prisms are equal.

Breaching- can occur during storms from waves destroying foredune ridge

Spit building(see image)- Spits naturally forming can create an inlet by partially closing off bodies of water

Drowned river valleys- many inlets can form in these valleys

Ephemeral inlets- Develop when lake levels overtop a barrier