Nature · Earth Science
Where land and ocean meet and battle
The coast is the dynamic frontier where land meets sea, constantly reshaped by waves, tides and currents. It hosts some of Earth's most varied scenery — from towering cliffs and sea stacks to sweeping sandy beaches and sheltered lagoons.
Coasts are shaped by two opposing processes. Erosion attacks headlands, prying open caves, arches and stacks and cutting cliffs back. Deposition builds the land up where waves lose energy, dropping sand and shingle to form beaches, spits and bars. The balance between them decides a coast's character.
Waves erode the cliff into a wave-cut platform on one side while depositing sand to build a beach and dunes on the other.
Gentle shores built by the waves
Where waves arrive gently, they drop their load of sand to build a beach. Wind then piles some of it into dunes that protect the land behind.
Where the sea attacks the land
On exposed coasts, waves undercut the rock until cliffs collapse and retreat, sculpting caves that become arches and, eventually, isolated sea stacks.
Ridges of sand reaching into the sea
Currents carry sand along the shore and drop it where the coast turns, extending a finger of land — a spit — that can grow to seal off a lagoon behind it.
Where rivers surrender to the sea
At the river's mouth, fresh and salt water mix over broad mudflats and marshes teeming with life — among the most productive habitats on Earth.