A free, self-paced textbook in 8 chapters. Read a chapter, then drill it with the 102 companion flashcards using spaced repetition.
The Pacific Ocean is the largest body of water on Earth, covering approximately 165.25 million km² — more than all of the world's landmasses combined. It also contains the deepest...
Beyond the five major oceans, the planet is dotted with smaller seas — many of them partially enclosed by continents or chains of islands. The Philippine Sea is the largest by area...
A handful of narrow waterways carry an outsized share of global trade, and their geography makes them both strategically vital and politically sensitive. The Strait of Gibraltar se...
Rivers are the arteries of the continents, carrying freshwater from highlands to oceans and shaping civilizations along their banks. The Nile River in Africa is generally regarded...
The Great Lakes of North America form the largest system of surface freshwater on Earth, and their names — Superior, Michigan, Huron, Erie, and Ontario — are remembered by the acro...
Ocean currents are the great rivers of the sea, redistributing heat around the planet and shaping regional climates. The Gulf Stream is one of the most influential: it originates i...
The ocean is divided vertically into distinct zones based on how much sunlight reaches them. The uppermost layer is the epipelagic, or sunlight, zone, extending from the surface do...
The rules governing who can do what on the sea are mostly set out in the United Nations Convention on the Law of the Sea, or UNCLOS, which was adopted in 1982 and came into force i...