Tectonic Earth:
The shape and geology of the Earth's surface is mainly the result of billions of years of slow shifting, making, and breaking of tectonic plates. Today, the plates are moving at 3/4 to 7 and 3/4 inches per year, the rate at which fingernails grow. The plates will continue to change throughout geologic time. This web page will cover seven major tectonic plates with information pertaining to their movement and formation throughout geologic time.
North American Plate:
The North American Plate covers 24 million square miles, but at one time, it was joined to the Eurasian, African, and South American plates until the former supercontinent of Pangaea started to break up and the Atlantic Ocean began to open. The relatively young mountains of western North America (Cascade Range) reflect ongoing subduction and collision with the Pacific Plate. Smaller active plates which surround the North American Plate are the Caribbean Plate, Cocos Plate, Rivera plate, and Juan de Fuca Plate. The Cocos and Rivera plates are currently subducting beneath the southern edge of North America to produce the active Mexican Volcanic Belt.
South American Plate:
The South American Plate covers 23 million square miles. Half of the plate is under the Atlantic Ocean. Down the west coast are the Andes which are thrust up as the South American Plate moves west over the subducting Nazca Plate that lies beneath the Pacific Ocean. The Nazca Plate is the fastest-moving of all plates, and as it dives steeply beneath South America, it generates earthquakes and volcanoes along the length of the Andes. Where these two plates collide (subduction zone), the 3,700 mile Peru-Chile trench has developed. The northern boundary of the South American Plate is covered by the waters of the Caribbean Sea, but its southern tip at Cape Horn is less than 600 miles from the Antarctic Circle.
Eurasian Plate:
The Eurasian Plate covers 35 million square miles and has the most complex history of its formation. To the west, the North American Plate is diverging away from the Eurasian Plate as the Atlantic Ocean continues to grow. To the east, both the Pacific and Philippine Sea plates are subducting beneath the Eurasian Plate. The two subducting plates have created an arc of volcanic islands that includes southern Japan and the Philippines. To the south, the Indian and Australian plates are moving north. The collision of the Indian plate with the Eurasian plate, some 60 million years ago, began pushing up the world's highest mountain range, the Himalayas. The Eurasian plate features geologic structures, such as the Mediterranean Sea, Tibetan Plateau, and Gobi Desert.
African Plate:
The African Plate covers 32 million square miles. Besides the African continent, the plate includes parts of the Atlantic, Indian, and Southern oceans. With the exception of the Atlas Mountain region in the northeast, much of the African continent has been warped into saucer-shaped basins and highlands. The north-western regions of the African continent is much lower in elevation and flatter. To the northeast lies the Arabian Plate. In more recent times, this plate split apart from the African Plate by the opening of the Red Sea, which is still growing wider at this time. Major geologic features for the African Plate include the Nile, Sahara Desert, East African Rift, and Mid-Atlantic Ridge.
Australian Plate:
The Australian Plate covers 18 million square miles. Australia, Antarctica, and New Guinea split apart from the other continents about 200 million years ago. Then Antarctica broke apart from Australia and New Guinea about 50 million years ago, leaving them both isolated. The gap between them is still growing. Due to its isolation, Australia is one of the most stable continents. The western plateau consists of ancient rocks known as the Precambrian shield. Many of these rocks date back anywhere from 570 to 3,500 million years ago. However, the oldest known rocks of Australia make up The Great Dividing Range, which formed hundreds of millions of years ago and is now extremely eroded.
Pacific Plate:
The Pacific Plate covers 42 million square miles, thus making it the largest of the tectonic plates. About 85 million years ago, the Pacific Plate was one of several in the Pacific Ocean, but as it widened and spread northwestward, the other plates were mostly subducted under the Americas. The plate's leading edge subducts sharply under the Eurasian, Philippine Sea, Australian, Caroline, and Bismarck plates, thus creating some of the world's deepest ocean trenches (e.g. Marianas Trench). The Pacific Plate is encircled by a string of active, often violently explosive volcanoes called the "Ring of Fire".
Antarctic Plate:
The Antarctic Plate covers 22 million square miles. The continent of Antarctica lies in the center of the Antarctic Plate. High mountain peaks are visible, but the continent is almost entirely covered with ice. Beyond the ice, the Antarctic Plate extends into the Southern Ocean for 1,000 miles or more in every direction. The Antarctic continent was once two plates (West Antarctica and East Antarctica); however, due to several surrounding spreading ridges, the two were joined together along a line joining the Ross and Weddell Seas. Geologic features include the Transantarctic Mountains, Ross Ice-Shelf, Crozet Islands, and Lambert Glaciers.