| This volcanism seemingly developed in an extensional setting near a shelf margin located in the eastern Neptune Range. |
| An active origin is suggested because volcanism and uplift appear to have preceded rifting, an active plume passing over a large area. |
| It was characterized by rhyolitic volcanism which appears to have been restricted to the Horn Graben area. |
| The volume, distribution and lithology of this volcanism, however, shows considerable differences between the two areas. |
| Geologically young, the Rockies exhibit faulting, glaciation, and volcanism, resulting in rugged, spectacularly scenic terrain. |
| This appears to contradict evidence from other areas, particularly Wales where subduction-related volcanism occurs in the late Tremadoc. |
