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Difficulty: MediumOceans, Coastal Processes, and Coastal Landforms

Arrange the following sequential stages in the formation and development of a coastal spit via longshore drift, starting from initial wave action to the creation of a recurved tip.

  1. 1Prevailing winds drive incoming waves to carry beach sediment obliquely up the shore face as swash.
  2. 2Gravity pulls the retreating backwash and sediment straight down the beach slope at a right angle to the coastline.
  3. 3Repeated zigzag movement (longshore drift) carries sediment past a sharp turn or estuary mouth into sheltered water.
  4. 4Accumulated sediment extends outward into open water, forming a narrow linear ridge attached to the land at one end.
  5. 5Secondary wind directions and wave refraction around the distal end bend the extremity of the sand ridge inland.

Answer

The correct order of stages in spit development is: 1) Waves driven by prevailing winds carry swash obliquely up the shore face, 2) Gravity pulls backwash straight down perpendicular to the coast, 3) Continuous longshore drift moves sediment past a bend in the coastline into sheltered water, 4) Deposition extends a narrow ridge of sediment outward into open water, and 5) Secondary winds and wave refraction curve the distal end of the ridge inland to form a recurved tip.
The development of a coastal spit begins with prevailing winds pushing wave swash obliquely up the beach face, followed by gravity pulling backwash straight down the slope perpendicular to the shore. This repeated cycle creates longshore drift, which carries sediment laterally along the beach face. When the drift reaches a break in the coastline, such as an estuary mouth or sheltered bay, reduced wave energy causes deposition. A linear sand ridge builds outward into open water, anchored at one end. Eventually, secondary wind forces and wave refraction curve the free distal end inland, producing a recurved spit with a hooked end.

Step-by-Step Solution

1
Identify the primary mechanism initiating lateral sediment movement along the shoreline.
Prevailing winds push waves toward the beach at an angle, propelling swash and sediment diagonally up the shore face.
Swash direction directly reflects the prevailing wind direction relative to the coastline.
2
Determine the path of sediment return during wave recoil.
Gravity pulls water and sediment straight down the slope of the beach perpendicular to the shoreline.
Gravity acts vertically down the steepest beach gradient regardless of wind angle.
3
Trace the movement of sediment as it encounters a change in coast orientation.
Longshore drift moves sediment past the corner of a headland or river estuary into calmer, deeper water.
Deposition begins when wave energy decreases in sheltered inlet waters.
4
Follow the structural growth of the deposited sediment body.
Continuous accumulation extends a narrow linear ridge of sand or shingle into the water, anchored to the mainland at one end.
Sediment builds up along the original line of drift past the mainland break.
5
Analyze how the final curved morphology of the landform develops.
Changes in prevailing wind direction and wave refraction around the open end push sediment inland, forming a hook.
Refracted waves alter the orientation of deposition at the unattached distal end.

Key Concept

Coastal spit evolution through longshore drift and wave refraction
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Topics

Oceans, Coastal Processes, and Coastal Landforms

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