Coastal Landforms: Formation and Characteristics

Coastal Formations

• Outward Flows: These extend from the coast to the deep sea, including gulfs and deep-sea starters near the coast.
• Cliffs: These are coasts that meet the sea with a steep drop. Sea erosion forms caves in the lower sections, wearing away areas of lower hardness to create sea arches. When the bottom of the cliff is pierced, or the top of the arch detaches, it can form sea stacks (Needle rock on the sea).
• Beaches: These are flat expanses with gentle slopes composed of sand, gravel, or pebbles, situated at the coast level. They consist of continental and marine sediments.
• Marine Terraces (The Shallow): These are marine erosion platforms parallel to the coast that have been elevated above lower sea levels. The flatter shapes represent the highest levels.
• Rias: These are coastal inlets formed by the sea invading the final stretch of a fluvial valley. This can result from a rise in sea level or the lowering of the continental crust.
• Wetlands: These are muddy plains found in bays, filled with sediment supplied by rivers flowing through them and by the sea during high tide, which covers and uncovers them at low tide.
• Coastal Arrows (Spits): These are sandbars that extend rectilinearly along the sandy coastline into the interior of a usually curved bay. Their landward end is often curved (hooked arrows). Arrows form due to the transport of sand along the coast into the bay. If an arrow completely closes off the bay entrance, it is called a coastal bar.
• Lagoons: These are salty coastal lakes separated from the sea by a sand cordon that closes off the bay. They often become clogged by salt marsh deposits and terrestrial inputs over time.
• Bars (Tombolos): These are sandbars joining the coast to a rocky islet. They can be double if two sandbars form, leaving a gap between them.
• Deltas: These are coastal outflows formed when a river deposits more sediment than the sea can redistribute, typically because the receiving body of water is calm, lacking strong currents or excessive waves.
• Dunes: These are sand mounds typical of sandy coasts. They form from the accumulation of sand transported by wind, which is then stabilized by vegetation. The profile of a dune is asymmetric: the windward face has a gentle, convex slope, while the leeward (sotovento) face is abrupt and concave. Dunes are oriented toward the prevailing wind.