As you stand at this overlook, look west. The area you see before you is commonly called the "Mississippi Delta". But did you know that technically the area is not a delta? It's part of an alluvial plain, created by regular flooding over thousands of years. Read the definitions below and see if you can tell the difference.
- Delta: a landform that is formed at the mouth or at the source of a river, where that river flows into an ocean, sea, estuary, lake, or reservoir
- Alluvial Plain: a largely flat landform created by the deposition of sediment over a long period of time by one or more rivers coming from highland regions
You can see by the above map that you are in the very top of the green section. Although commonly called The Mississippi Delta, this land area is actually part of an alluvial plain. Standing at the posted coordinates, you will notice that you are at the edge of the bluff. As you survey the land in front of you, you should notice one defining feature. It's completely FLAT from here to the Mississippi River! The entire green section of the map shares this characteristic. The lands below you contain some of the most fertile soil in the world. Why is this so? As the lands upriver erode due to weathering and water flow, the sediment from the hills is transported to the lower plains you see here in front of you. The flooding river deposits sediment such as gravel, silt, minerals, sand, and rocks into the flood plains. These sediments are called alluvium. Although flooding of the Mississippi River can be partially controlled by man-made structures, flooding of this area still occurs. The last major flood took place in Spring 2011, causing the most damage seen since the 1927 flood.
Look back at the map above. Notice the pink area located on the western border of the Mississippi river. This is called the Mississippi River Embayment. This area is defined as a sedimentary basin. This means that these lands exhibit infilling by sedimentation. As these sediments are buried, they are subjected to increasing pressure and begin the process of lithification (which is the process whereby freshly deposited loose grains of sediment are converted into rock.)
Finally, look a the purple area on the above map. The true Mississippi River Delta is the area of land built up by alluvium deposited by the Mississippi River as it slows down and enters the Gulf of Mexico. The deltaic process has, over the past 5,000 years, caused the coastline of south Louisiana to advance gulfward from 15 to 50 miles.
To claim credit for this cache:
Please email the answers to the following questions to owner. Do this by clicking on my profile. Do not post your answers in your logs. Logs submitted without an accompanying email will be deleted. No "arm chair" logs please, you must physically visit the cache site.
1. Take an elevation reading at the posted coordinates located at the top of the bluff. How much higher is the top of the bluff when compared to the rich, flat farm land of the delta below? (Don't climb down the bluff to get the lower reading. Just drive down as you leave, and take an elevation reading anywhere in the delta. It's flat, so you can take that reading anywhere once you drop off the bluff)
2. Explain, in your own words, the difference between a true river delta, and the land you see stretched out before you.
3. (Optional) Please post a photo of you and your gps unit overlooking the fertile lands of the Mississippi Delta.