| Northwestward movement of Baja California, with accompanying
distortion of the Sierra Nevada and Klamath blocks, exerted
tensional stress on the Basin and Range province
between 10 MYA and recent time. Twisted by
northward pressure, the Sierra Nevada tilted more to the
west. Released from horizontal confining forces,
previously fractured Basin and Range blocks rotated to form
ranges and valleys. At the northern extreme of the
Basin and Range, Columbia Plateau flood basalts were
released, possibly where Basin and Range blocks detached from
relatively unfractured crust. |
