As the Mississippi River enters the Gulf of Mexico, it loses energy and dumps its load of sediment that it has carried on its journey through the middle of the North American continent. This pile of sediment, or mud, accumulates over the years building up the delta front. As one part of the delta becomes clogged with sediment, the delta front will migrate in search of new areas to grow. The area shown in this false-color image is the currently active delta front of the Mississippi. The migratory nature of the delta forms natural traps for oil. Most of the land in the image consists of mud flats and marsh lands. There is little human settlement in this area due to the instability of the sediments. The main shipping channel of the Mississippi River is the broad stripe running northwest to southeast. This scene covers an area of 54 by 57 km, and was acquired on May 24, 2001 by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) aboard NASAs Terra satellite.
Time, weather, and human intervention have all shaped the Mississippi Delta in Louisiana, a giant bird’s foot shape protruding into the Gulf of Mexico. The Mississippi River deposits sediment into the ocean, and over 25 years, NASA Landsat satellites observed changes in the delta’s shape.
The Ebro River Delta, located along the eastern coast of Spain, is one of the largest wetland areas (320 km²) in the western Mediterranean region. The Ebro delta has grown rapidly—the historical rate of growth of the delta is demonstrated by the city of Amposta. This city was a seaport in the 4th Century, and is now located well inland from the current Ebro river mouth. The rounded form of the delta attests to the balance between sediment deposition by the Ebro River and removal of this material by wave erosion. This astronaut photograph, taken in partial sunglint, also shows the Ebro’s fresh water lens—the water density boundary between the upper layer of fresh water issuing from the Ebro River mouth and the saltier, denser Mediterranean Sea water.