Spectacular was this outburst in its time, and profound was its influence upon later scenery, but short was its duration. Before weather could redden the lava surface, streams washed gravel over it; and only at the main centers between the Mount Holyoke Hotel and the Amherst-South Hadley road were the volcanoes able to hold out against the relentless activity of running water. The block east of the rift continued to move southward and to rise, while the streams draining it entrenched themselves in an effort to remain at grade with the basin floor. The moving mountain mass pushed the lava flow up on end and twisted its eastern edge around, dragging it along to the south. The rock splinters which were formed in the process sliced the basin sediments into small blocks, some of which can be seen north of Turners Falls and also at the Holyoke Range. Ultimately the upward and southwestward movement along the rift piled the eastern blocks against the more westerly ones, pushing the west side of each eastern block up on the east side of the adjacent western one, and depressing its eastern side more deeply into the basin floor. The many fractures which were made weakened the basalt lava sheet along certain zones where, in recent time, the elements have worn the notches in the Holyoke Range. [Illustration: Fig. 19. _Block diagram showing the main features of central New England at the opening of the Cenozoic era._] [Illustration: Fig. 20. _Block diagram showing the main features of central New England at the present time._] Streams from the eastern highland stubbornly filled up the holes and planed off the raised blocks during the entire period of intermittent movement. In the midst of the tussle between earth forces and fluvial agents the volcanoes again broke into explosive eruptions, and volcanic ash filled many of the block-like depressions all the way from Granby to localities south of Holyoke. Then the fiery vents cooled, and the earth movements diminished in their vigor. But they left a mountain front so steep that talus and landslide deposits accumulated at its base near Mount Toby; and the block mountain range was so high that glaciers may have wreathed its summit. The mountain mass descended southward, and it was penetrated by at least one low pass northeast of Granby.