Arrange the following stages of coastal deposition and feature evolution in the correct chronological order, from the initial sediment transport mechanism to the final development of a sheltered wetland ecosystem.
- 1Longshore drift moves littoral sediment laterally along the shoreline until reaching a sudden change in coastal orientation, such as an estuary or bay mouth.
- 2Sediment drops out of transport into deeper water, extending a long, narrow sand ridge outward from the mainland.
- 3Wave refraction and secondary wind directions curve the outer end of the extending ridge inland toward the coast.
- 4Fine silt and organic debris settle in the low-energy lagoon trapped behind the protective feature, forming a salt marsh.
Answer
The correct sequence begins with longshore drift carrying sediment along the coast, followed by the extension of a spit into open water, the curvature of the spit terminus into a hook due to wave refraction, and finally the settlement of fine silt behind the sheltered spit to form a salt marsh.
The formation of a coastal spit and its associated salt marsh follows a strict chronological sequence. Longshore drift first transports sand and shingle along the shoreline. As the sediment reaches an estuary or bay where wave energy drops, deposition occurs, causing a narrow landform (spit) to project into open water. Subsequent wave refraction or prevailing wind shifts curve the tip of the spit inland into a hook. Finally, in the quiet, low-energy water trapped behind the spit, fine silt and mud settle out, eventually colonizing with vegetation to form a salt marsh.
Step-by-Step Solution
Key Concept
Coastal Depositional Processes and Spit Evolution