Definition
A cape is a piece of land that sticks out sharply into the sea. A bay is the opposite: a curve of sea that cuts inward into the land. When a coastline winds like the teeth of a gear or like interlaced fingers, the parts that reach out into the water are capes and the parts that tuck in are bays.
The Fist Reaching Into the Sea: Capes and Rough Waves
Travel along a coastline and you will meet land that juts into the sea like a rhino's horn or a fist. The tip of land that stretches out into the water like this is called a cape. In Korea, famous sunrise spots such as Homigot in Pohang and Ganjeolgot in Ulsan are capes. (The Korean word for cape is "got.")
Because of their shape, capes take the full force of the waves from every side. When water hits the protruding land, the waves' energy gets focused on one spot. So rock is constantly and violently broken down and worn away. That process is called erosion.
That is why capes usually have steep cliffs and tall rock pillars instead of soft sandy beaches. The rough water makes it dangerous to dock a boat. But the open view in every direction makes a cape the perfect place for a lighthouse that guides ships far out at sea.
The Gentle Embrace: Bays and Calm Sandy Beaches
Keep going between two capes and you reach a place where the sea curves in, hugged by the land on all sides. A sea that is hollowed out and surrounded by land like this is called a bay. In Korea, Suncheon Bay, Yeongil Bay, and Garorim Bay are well-known examples. (The Korean word for bay is "man.")
The capes on both sides act like breakwaters, taking the rough waves and storms head-on. Thanks to them, the water inside a bay is as calm and peaceful as a lake. As the waves lose their strength, they gently drop the fine sand and mud they carried from far out at sea. This is called deposition, and it happens a lot in bays.
That is why bays often have sandy swimming beaches or wide tidal flats, which are home to sea creatures. Because the water is calm, bays have also long been used as natural harbors where ships can safely drop anchor. But a shallow bay that has piled up lots of sediment, like a tidal flat, is hard for large ships to enter.
A Bit More Precisely: Coastlines Smooth Themselves Out
So will capes and bays stay exactly as they are forever? Actually, nature is always at work straightening out the bumpy coastline.
A cape, which faces the rough waves alone, loses rock over time and slowly retreats toward the land. Meanwhile, the rock fragments and sand worn off the cape are carried by the waves into the bay, where they pile up bit by bit and slowly fill in the hollow of the sea.
Over tens of thousands to millions of years, the jutting cape is worn down and lowered, and the tucked-in bay fills with sand and mud. So the longer the time that passes, the more the coastline changes from a jagged, gear-tooth shape into a smooth, nearly straight line.
Common misconceptions
Capes and bays have fixed rock and sand in fixed places, so their shapes never change.
Waves keep wearing down capes and filling bays with sand, so over tens of thousands of years a coastline gradually becomes a gentler, straighter line.
Where you meet it
Many of the famous sunrise spots on Korea's east coast, such as Homigot and Ganjeolgot, are capes that stick out into the sea.
The wide tidal flats of Suncheon Bay and calm trading ports sit in bays, where the sea tucks into the land.
In one sentence
A cape is land that sticks out into the sea and gets worn away by waves. A bay is sea that cuts into the land, where sand settles quietly.