Rocks of different origins and ages occur in three fundamentally different geological provinces
Bulk chemical composition of continents difficult to determine accurately, but we estimate:
Taking the elevation of 1 km below sea level as edge of continents, roughly 40% of earth’s crust is continental
Ocean basins
Ocean floors are so dominated by basalts that the bulk chemical composition of oceanic rock is relatively easy to estimate:
Oceanic rocks are uniformly younger than 200 Ma old
Unique geomorphologic features in ocean basins
Continental shelves, slopes and rises are dissected by submarine canyons
The remaining geomorphic features in ocean basins (found in the abyssal plains) correlate with and correspond to three distinct geological provinces
Mid-ocean ridges (MORs)
Mid-ocean ridges (MORs), continued
Email: steven.wojtal@oberlin.edu
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