The observer will also notice that Catharina, the huge pit at the
southeastern end of the chain, bears evidence of yet greater age. Its
original walls, fragments of which still stand in broken grandeur,
towering to a height of 16,000 feet, have, throughout the greater part
of their circuit, been riddled by the outbreak of smaller craters, and
torn asunder and thrown down on all sides.
In the vast enclosure that was originally the floor of the
crater-mountain Catharina, several crater rings, only a third, a
quarter, or a fifth as great in diameter, have broken forth, and these
in turn have been partially destroyed, while in the interior of the
oldest of them yet smaller craters, a nest of them, mere Etnas,
Cotopaxis, and Kilaueas in magnitude, simple pinheads on the moon, have
opened their tiny jaws in weak and ineffective expression of the waning
energies of a still later epoch, which followed the truly heroic age of
lunar vulcanicity.
This is only one example among hundreds, scattered all over the moon,
which show how the surface of our satellite has suffered upheaval after
upheaval. It is possible that some of the small craters, not included
within the walls of the greater ones, may represent an early stage in
the era of volcanic activity that wrecked the moon, but where larger and
smaller are grouped together a certain progression can be seen, tending
finally to extinction. The internal energies reached a maximum and then
fell off in strength until they died out completely.
Pages:
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174