Progradation
In sedimentary geology and geomorphology, the term progradation refers to the growth of a river delta farther out into the sea over time. This occurs when the mass balance of sediment into the delta is such that the volume of incoming sediment is greater than the volume of the delta that is lost through subsidence, sea-level rise, and/or erosion.
Progradation can be caused by:
- Periods of sea-level fall which result in marine regression. This can occur during major continental glaciations within ice ages, be caused by changes in the rates of seafloor spreading that affects the volume of the ocean basins, or tectonic effects on the regional mantle density structure that can change the geoid elevation.
- Extremely high sediment input, such as by the Huang He (Yellow River) in China, which drains the Loess plateau, or from high sediment loads in proglacial rivers.
See also
- Retrogradation – Movement of the front of a river delta inland over time
- River delta – Silt deposition landform at the mouth of a river
- Aggradation – The increase in land elevation due of the deposition of sediment
- Marine transgression – Geologic event in which sea level rises relative to the land
- Marine regression – A geological process of areas of submerged seafloor being exposed above the sea level.
- Sedimentology – The study of natural sediments and of the processes by which they are formed
- Stratigraphy – The study of rock layers and their formation
- Sequence stratigraphy – Study and analysis of groups of sedimentary deposits
- Sediment transport – The movement of solid particles, typically by gravity and fluid entrainment
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