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Comment: 23:35 - 24:36 (01:01)
Source: Annenberg/CPB Resources - Earth Revealed - 7. Mountain Building
Keywords: continent, "ocean basin", craton, mountain, accretion, margin, rift, collision, "Jason Saleeby"
Our transcription: Through geologic time, the amount of continental material on Earth has slowly grown in size at the expense of the ocean basins.
But tracing the history of growth on individual continents is a great challenge for each continent today has been joined to other continents in the past.
The general pattern in continents is to find the oldest material in the interiors of the cratons, and this is because the cores of the continents formed and then successive mountain belts and continent-edge accretions occurred around their margins.
But geologists find that pattern to be imperfect because continental masses tend to break and rift apart during their growth.
And so if they break apart, they may break apart across older interiors of continents across younger mountain belts, and then subsequently they may form a new mountain belt across a broken edge.
So that leaves us with a competing series of processes of marginal growth, and breaking apart and drifting, and then colliding back together and growing again.
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