Catastrophic Revelations - The Rocks Don't Lie - page 107

ley walls. Scrope's careful observations left no doubt that the lava had repeatedly filled a
valley that the river just as often reexcavated. The layers exposed in the cliffs were not de-
formed and there was no evidence of catastrophic disruption. The valley-filling lava flows
could be traced back to loose cinder cones sure to have been swept away by a flood capable
of carving into hard rock.
Lava flows emplaced over buried river gravels in Auvergne, France ( based on Charles Lyell's 1833 Principles of
Geology , volume III, figure no. 61, p. 267 ).
The following May, Lyell set off to explore the region firsthand, accompanying the in-
fluential Scottish geologist Roderick Murchison on an excursion through France. They vis-
ited Scrope's outcrops and studied the relationships between cinder cones, basalt flows, and
river terraces. It quickly became clear to Lyell that a single flood could not have carved
modern topography. Rivers slowly carved their own valleys.
From Auvergne, they traveled down the Rhone Valley to compare its rocks with those
of the Paris Basin. Proceeding south into northern Italy, they traveled from Bologna to
Florence and on to the Zoological Museum in Turin. Lyell realized that the rocks in the dif-
ferent parts of the regions they had just crossed had different fossils. Here was a formative
realization for one who had never set out to become a geologist.