Major Lithospheric Plates of the Earth. CREDIT: USGS This Dynamic Earth
Scanning the map, you'll note that plate boundaries run across ocean basins, or along the edges of continents and ocean basins, and in places, across continents and islands. We'll learn more later about the nature of these boundaries. For now, appreciate that the mid-ocean boundaries are places where the sea floor spreads apart, and magma comes up along the seam to solidify into new sea floor. Other boundaries are places where plates collide. One type of collisional boundary happens where continental material crumples together in great mountain ranges. Along other collisional boundaries, which involve at least one side with ocean floor, volcanic activity flourishes where an oceanic plate subducts (dives down) under the other plate.
North American -- Includes North America, part of Siberia, and Greenland. Includes half the North Atlantic ocean basin, the Arctic ocean basin, and the ocean floor around Alaska and Siberia.
Pacific -- Includes no continents, only small islands like the islands of Polynesia and Hawaii.
Juan de Fuca -- Just a patch of sea floor off Washington and Oregon.
Cocos -- Includes the sea floor from Baja, Mexico down to central America.
Nazca -- Includes the sea floor on the Pacific side of South America.
Caribbean -- Includes the sea floor of the Caribbean Sea, hugging South America.
South American -- Includes South America and half the South Atlantic ocean basin.
Scotia -- A strip of South Atlantic sea floor off the tip of South America.
Antarctic -- Includes the continent of Antarctica and the surrounding sea floor.
African -- Includes Africa, except for Arabia, plus the sea floor in half the Atlantic ocean basin and half the Indian ocean basin, which includes the island of Madagascar off eastern Africa.
Arabian -- Includes the Arabian peninsula, which has the Red Sea along its southern border.
Indian -- Includes India, which is bounded by the Himalayas to the north, and the sea floor of the Indian ocean basin around India.
Australian -- Includes Australia plus a good bit of the Indian ocean basin and parts of the Pacific ocean basin.
Eurasian -- Includes Europe, most of Asia, and bordering areas of sea floor in the North Atlantic, the Mediterranean Sea, and the edge of the Pacific ocean basin.
Philippine -- Includes a diamond-shaped patch of the western Pacific ocean basin.