Dalziel, Ian W. O. Department of Geological Sciences, University of Texas, Austin, Texas.
- Links to Primary Literature
- Additional Readings
The six major continents are Africa, Antarctica, Australia, Eurasia, North America, and South America. The high elevation of these discrete masses of rock, relative to the floor of the oceans, results from their low density. Each continent is embedded within denser rock forming one of the seven rigid 100-km-thick (60-mi) lithospheric plates making up the cold surface layer of the planet. The Pacific plate is purely oceanic. The plates, and therefore the continents, are moving relative to one another. Prior to the formation of the Atlantic, Indian, and Southern ocean basins over the past 180 million years by the process known as sea-floor spreading, the continents were assembled in one supercontinent called Pangea (literally “all Earth”; Fig. 1). Pangea came together by the collision, about 300 million years ago (MYA), of two smaller masses of continental rock, Laurasia and Gondwanaland. Laurasia comprised the combined continents of ancient North America (known as Laurentia), Europe, and Asia. Africa, Antarctica, Australia, India, and South America made up Gondwanaland (this name comes from a region in southern India). The term “supercontinent” is also applied to Laurasia and Gondwanaland; hence it is used in referring to a continental mass significantly bigger than any of today's continents. A supercontinent may therefore incorporate almost all of the Earth's continental rocks, as did Pangea, but that is not implied by the word. See also: Continent; Continents, evolution of; Plate tectonics
The content above is only an excerpt.
for your institution. Subscribe
To learn more about subscribing to AccessScience, or to request a no-risk trial of this award-winning scientific reference for your institution, fill in your information and a member of our Sales Team will contact you as soon as possible.
to your librarian. Recommend
Let your librarian know about the award-winning gateway to the most trustworthy and accurate scientific information.
AccessScience provides the most accurate and trustworthy scientific information available.
Recognized as an award-winning gateway to scientific knowledge, AccessScience is an amazing online resource that contains high-quality reference material written specifically for students. Contributors include more than 9000 highly qualified scientists and 43 Nobel Prize winners.
MORE THAN 8500 articles and Research Reviews covering all major scientific disciplines and encompassing the McGraw-Hill Encyclopedia of Science & Technology and McGraw-Hill Yearbook of Science & Technology
115,000-PLUS definitions from the McGraw-Hill Dictionary of Scientific and Technical Terms
3000 biographies of notable scientific figures
MORE THAN 19,000 downloadable images and animations illustrating key topics
ENGAGING VIDEOS highlighting the life and work of award-winning scientists
SUGGESTIONS FOR FURTHER STUDY and additional readings to guide students to deeper understanding and research
LINKS TO CITABLE LITERATURE help students expand their knowledge using primary sources of information