Comment: 13:27 - 14:37 (01:10)
Source: Annenberg/CPB Resources - Earth Revealed - 7. Mountain Building
Keywords: subduction, accretion, mountain, orogeny, lithosphere, India, Asia, "ocean basin", collision, "sedimentary rock", "metamorphic rock", "igneous rock", "convergent plate margin", Madagascar, Fiji
Our transcription: Subduction of sea floor is the most common reason mountains form, but it is not the only way.
Another method is "accretion" the joining together of separate land masses.
When two masses of continental lithosphere, such as India and Asia are brought together by the complete subduction of an intervening ocean basin, the collision raises huge mountains.
Sea floor and sedimentary deposits caught in the squeeze are metamorphosed and converted in part to igneous rock.
This process glues the once separate land masses together.
The accretion of two such large bodies of lithosphere as India and Asia is not a common geological event, but there is evidence that much smaller bodies of land are frequently added to the margins of continents by subduction.
Small continental fragments, such as Madagascar and the Fiji Islands are scattered throughout the world's oceans.
Geology School Keywords