21. At this point basaltic oceanic crust begins to form between the separating continental fragments. 22. The feature they apparently formed is a 180-degree structure contains young oceanic crust exclusively. 23. The island is made of oceanic crust that formed at the Macquarie Triple Junction. 24. The North American Plate includes both continental and oceanic crust . 25. The islands rise from Jurassic oceanic crust associated with the opening of the Atlantic. 26. Most oceanic crust in the ocean basins is less than 200 million years old. 27. The last rocks to be slid across were slabs of oceanic crust , mainly basalt. 28. That, anyway, is classical plate tectonic theory, and it works fine for oceanic crust . 29. The oceanic crust is made up of rocks much younger than the Earth itself. 30. The oceanic crust is 99 % basalt, which is an igneous rock of mafic composition.
