The floor on which the ash came to rest was not everywhere the same. Where now it crosses the Northampton-Holyoke highway and the Amherst-South Hadley road it was a lava flow; but north of Granby and at numerous places between the Hockanum and Amherst-South Hadley roads the ash lies on conglomerate. Along the Amherst-Springfield power line, a block of the conglomerate floor was pushed up five hundred feet above the same beds farther west, forming a small block mountain which was entirely buried beneath the ash. Similar block mountains can be observed under the blanket of ash, especially on the south side of the Holyoke Range; and renewed movement subsequently affected many of the blocks north of Granby, where the ash deposit and even some of the sediments laid down in the earlier days of the dinosaurs were fractured and displaced. As a rule, along any one fault, the block on the east was pushed up and moved southward; and the block on the west was pressed down: as a group, the fractures may form the beginning of the great eastern border fault which bounds the basin farther south. The volcanoes which made the Granby tuff or ash bed erupted intermittently for a long period of time. Usually, the river which emerged from the eastern mountain range brought so much fluvial debris that ash is not in evidence except in the immediate vicinity of the craters located between the Notch and the summit of Mount Holyoke. Even though alluvial sands and gravels supplant the tuff here and there, the river did not succeed in closing or quenching those fiery vents. The rocks now present recount a struggle in which, at times, the river encroached upon the cinder cones; at others, the ashes choked the stream and buried its alluvial wash. While the volcanoes rumbled and erupted, earth forces intermittently thrust the eastern mountain range southward and upward, dragging the eastern margin of the lowland with it and upturning the sedimentary fill, much as a plow might upend a layer of snow at the roadside before shearing it off and pushing it out of the way. The relentless movement caused the entire eastern floor of the basin to be broken into blocks; the easterly ones were piled against the westerly, and their eastern edges were pushed down into the basin floor and the western borders rode up on their neighbors. Through all this tremendous disturbance the great stream pouring out of the mountain pass kept the elevated blocks cut down and the small basins filled in. Earthquakes, erupting volcanoes, and shifting rivers made life for the dinosaurs troubled and a bit uncertain.