Rias:
A ria is a coastal inlet formed by the partial or complete submergence of an river valley that was not formed by glaciers. It is a drowned river valley that remains open to the sea. Typically, rias have a treelike outline although they can be straight and without significant branches. This pattern is inherited from the dendritic drainage pattern of the flooded river valley. The drowning of river valleys along a stretch of coast and formation of rias results in an extremely irregular and indented coastline. Often, there are islands, which are summits of partly submerged, pre-existing hill peaks. The sea level change that caused the submergence of a river valley may be either eustatic (where global sea levels rise), or isostatic (where the local land sinks). The result is often a very large estuary at the mouth of a relatively insignificant river (or else sediments would quickly fill the ria).
Estuary:
An estuary is a geomorphological designating one of the possible forms the mouth of a river, when a coastal valley is submerged by rising sea water level. It is an arm of the sea, which flows into the sea and which is subject to tidal action.
Local Geology:
Delaware Bay is the estuary outlet of the Delaware River it is 782 square miles in total area. The shores of the bay are largely composed of salt marshes and mud flats. Besides the Delaware, it is fed by numerous smaller streams which give it a tree like outline on the map. The bay is for the most part shallow with some deeper parts.
So what happened to this valley? Was it a valley protected by a mountain/cliff of rock along the shoreline where coastal erosion eroded away the rock or was it the river that eroded it away? Was it a rising of the ocean? Well it is not 100% known, but with resent history of the coast line we can hypothesis what did happen. The ocean is rising but slowly. The main effect here is the coastal erosion that has drastic effects on the coast line over a short time period. And if we combine that with the erosional effect of a river well you get the picture. It is estimated, that this area was dry about 21,000 years ago. The effects of coastal erosion can be measured throughout the history in this area. The Ocean is washing away at the shore lines along the peninsula of Cape May and along the shorelines around the areas on both sides of the Delaware Bay area.
What is Erosion?
Erosion is the process by which soil and rock are removed from the Earth's surface by natural processes such as wind or water flow, and then transported and deposited in other locations.
Types of Erosion:
Source: http://102supercoastswiki.wikispaces.com/file/view/headlands_and_bays7.jpg/232666296/headlands_and_bays7.jpg
Splash Erosion: Small soil particles are detached and sent airborne through the impact of raindrops on soil.
Sheet Erosion: Raindrops break apart the soil structure and it's moved down-slope by water that flows overland as a sheet rather than definitive channels. This occurs frequently during cloud bursts.
Rill Erosion: This process develops small, short-lived, concentrated flow paths. These paths create a sediment source and delivery system for hill-slope erosion. Areas where precipitation rates exceed soil infiltration rates are more prone to this type of erosion.
Gully Erosion: Water flows in narrow channels during or directly following heavy rains or melting snow. The gullies can erode to considerable depths.
Valley or Stream Erosion: Continual water flow alongside land (along a linear feature) creates this type of erosion. It extends downward, deepening a valley, and head-ward, extending the valley into the hillside. This occurs most frequently in times of flooding.
Bank Erosion: Over time, banks of rivers and streams are naturally worn down.
Freezing and thawing: Cold weather causes water trapped in tiny rock cracks to freeze and expand, breaking the rock into several pieces.
Wind erosion: is of two primary varieties: deflation, where the wind picks up and carries away loose particles; and abrasion, where surfaces are worn down as they are struck by airborne particles carried by wind.
Urbanization: has major effects on erosion processes—first by denuding the land of vegetative cover, altering drainage patterns, and compacting the soil during construction; and next by covering the land in an impermeable layer of asphalt or concrete that increases the amount of surface runoff and increases surface wind speeds.
Shoreline erosion primarily occurs by the actions of the currents and waves.
Hydraulic action happens when the force of moving water currents rushing into a crack in the rock. The water compresses the air in the crack. As the wave retreats, the highly pressurized air is suddenly released with explosive force, capable of chipping away at the rock over time. Thus, the crack is gradually widened so the amount of compressed air increases, and hence the explosive force of its release increases.
Wave pounding is when the sheer energy of the wave hitting the cliff or rock breaks pieces off.
Abrasion or corrasion is caused by waves launching seaload at the cliff. It is the most effective and rapid form of shoreline erosion (not to be confused with corrosion).
Corrosion is the dissolving of rock by carbonic acid in sea water. Limestone cliffs are particularly vulnerable to this kind of erosion.
Attrition is where particles/seaload carried by the waves are worn down as they hit each other and the cliffs. This then makes the material easier to wash away. The material ends up as shingle and sand.
Sources
- Myers, Albert Cook, ed. Narratives of Early Pennsylvania, West New Jersey, and Delaware, 1630 -1707. (New York, NY: Charles Scribner's Sons. 1912)
- Ward, Christopher. Dutch and Swedes on the Delaware, 1609 – 1664 (University of Pennsylvania Press. 1930)
- Leiby, A. C. The Early Dutch and Swedish Settlers of New Jersey (Princeton: D. Van Nostrand Co. 1964)
**Logging requirements**
DO NOT POST ANSWERS IN YOUR LOG.
Send the following answers to me via email.
- The text "GC5EJ6R Ria" on the first line
- How wide is this Ria? (see waypoint "Other side")
- Looking up the bay at 330 degrees what is seen on the horizon which is using the water, and do you think it is affected by the tidal action of the bay?
- Do you think this ria is “eustatic” or “isostatic”? (see depth chart above)
At waypoint "Control"
- Humans are trying to control erosion, how?
- What size makes up the general size of this erosional control feature?
At waypoint "Nature"
- Nature is starting to take over erosion control here, how?
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