Prior to the Eocene Epoch (55.8 ± 0.2 to 33.9 ± 0.1 Ma), the convergence rate of the
Farallon and
North American Plates was fast and the angle of subduction was shallow. During the
Eocene, the Farallon Plate
subduction-associated compressive forces of the
Laramide orogeny ended, plate interactions changed from orthogonal compression to oblique strike-slip, and volcanism in the Basin and Range Province flared up. It is suggested that this plate continued to be underthrust until about 19 Ma, at which time it was completely consumed and volcanic activity ceased, in part.
Olivine basalt from the
oceanic ridge erupted around 17 Ma and
extension began. The extension resulted in roughly north-south-trending faults, the
Great Basin, the
Walker trough, the
Owens graben, and the
Rio Grande rift, for instance. ==List of large-volume eruptions in the Basin and Range Province==