What Is a Bay? Definition, Formation & Examples

A bay is a body of water partially enclosed by land, connected to a larger ocean, sea, or lake. Bays are typically smaller than gulfs and feature sheltered waters, making them ideal for harbors, recreation, and ecosystems.

Formation Processes

• Coastal Erosion: Waves and currents wear away softer rock, leaving harder headlands that frame a bay.
• Glacial Carving: Retreating glaciers carve U-shaped valleys that flood as sea levels rise (fjords are a type of bay).
• Tectonic Subsidence: Land sinking along fault lines creates coastal indentations.
• Sea-Level Rise: Post-glacial flooding of river valleys forms drowned coastlines (rias).

Key Features

• Calmer waters than open ocean
• Often rich in biodiversity (estuaries, wetlands)
• Natural harbors for ports and settlements
• Popular for swimming, fishing, boating, kayaking

Famous Examples

• San Francisco Bay, California, USA
• Bay of Bengal, Indian Ocean
• Hudson Bay, Canada
• Bay of Fundy, Canada (highest tides)
• Guanabara Bay, Rio de Janeiro, Brazil