"On human time-scales, continental rifting
is extremely slow at spreading rates of mm's per year but, on geologic time-scales, rifting
can be considered a catastrophic continental breakup event."
Thus, the continent--ocean transition is more complex than previously thought, and depth-dependent stretching and/or simple shear have been invoked to explain how mantle could be exhumed during the rifting
process, and lead to asymmetrical conjugate margins.
Finding the rift extension led the team to propose that the mountains are actually the result of multiple orogenies, or mountain building episodes, involving a unique combination of continental collision, rifting
and uplift processes not previously seen together in other mountain ranges.
The reappearance of banded iron is more likely related to episodes of continental rifting
in the Neoproterozoic and deposition in enclosed or restricted rift basins close to hydrothermal vents along incipient mid-ocean ridges.
He notes that some flood basalts might be related to continental rifting
, but he says the eruptions cause rifting
-- an idea in direct opposition to the theory that rifting
causes flood basalts.
"This work is a breakthrough in our understanding of continental rifting
leading to the creation of new ocean basins," said Ken Macdonald, professor emeritus in the Department of Earth Science at the University of California, Santa Barbara, and who is not affiliated with the research.
The age and style of rifting
describe the nature of the continental breakup phase preceding orogeny.
Previously, scientists seeking to explain the origin of this break have been unable to choose between two rival rifting
theories, but geophysicists recently pulled up evidence from the ocean floor that they say settles the debate.