The Salt Lake herald. [volume] (Salt Lake City [Utah]) 1870-1909, 1899-07-12
POPULAR LECTURES
IN PHYSICAL SCIENCE.
III. CHANGES OF THE EARTH'S
SURFACE AND ANIMAL LIFE.
BY ALPHEUS SPRING PACKARD,
NJ. D., PHI. D.

| M. D., PHI. ID.
| Our earth is only less stable than the
\ sea- Its crust or outer layer of rocks
| has from the earliest ages been repeat
edly crumpled, folded and either raised
| into vast plateauS over certain regions
or depressed in other areGs, there
| forming the bottom of the oceans. AT
the outset it is probable thai the sea
covered the whole globe, with here and
there, especially in the northern hemis-
phere, islands destined TO form the nu-
clei of the continents now rising above
its surface. Since that early period
there has been a constant struggle be-
tween the terrestrial and oceanic
powers, but the land has steadily
gained upon the sea. There have, how
ever, locally been extensive and wide
spread invasions of the land by the sea,
though upon the whole the present
great oceans have from their earliest
times been confined to their present
portions, however, along the great
coast lines, the changes of level
have involved enormous eXtents of land
and sea, the elevation of certain re-
gions and the depression of others ex-
tending through thousands of feet.
1t can therefore be well imagined
what a profound influence these
changes must have had on the animals
Changes such as these in the physical
geography of the globe were evidently
the primary factors in the modifica-
ton and evolution of life forms.
Let US examine in some detail GER
tain of the great geological changes
and not the very probable effect they
must have had on the origin not only
of varieties and species but even Of
families and orders, as well as classes
Of mi &c tor hn
extinction of numerous important types
of life was with little doubt due to
widespread geological changes, such as
the gradual upheaval of mountain
chains, the ice period and other climatic
changes due to elevations and sinkings
of land, and why may not the origin Of
the new forms succeeding them have
been due to the same changes? We
know that throughout geological his
tory there have been progressive
changes in the building UP of the con-
tinents, and that throughout all time
there has been corresponding pro-
greSsive development of life forms-a
process of differentiation from the SIM
pie and generalized to the more COM
pick or specialized, a gradual evolution
from monad to man.
Our knowledge is very limited as to
what took place between the time when
our earth cooled down, assumed its
present size and shape and became fit
ted for life, and the period known as
the Cambrian, when the principal types
of animals, with the exception Of rep
tiles. birds and beasts, had appeared.
Indeed, we know almost nothing at all
definite about it. But it will be readily
seen that this was the most important
and productive period in the life of our
earth.
During this immensely long pre-
Cambrian age, including the Lauren
tian and Algonkian periods of geolo-
gists, what extent of land there was,
was subjected to the most radical and
widespread changes. We know little
of them, as their effects have only been
studied in limited spots near Lake Su-
perior and elsewhere, but there must
have been repeated revolutions. This
is proved by the highly contorted and
disturbed Archean (Laurentian) rocks,
GRANTEES and sneiss which have been
observed at different points in North
America, lying beneath the relatively
less disturbed Algonkian series.
At a later time between the pre-
Cambrian and Cambrian periods there
was, according to Walcott, a great up
lift and folding of strata; the elevated
plateau thus formed, with it's mountain
ranges, extending perhaps for thou
sands of miles over the then continent,
was carved into mountain peaks, chile
these were worn down by the idins,
and the rivers cutting through them
carried the debris into the sea.
One might think that the earth in
these primeval times was too much
disturbed and untitled for the existence
of life. But that plants and animals
did exist is suggested by the occurrence
of beds of graphite. which is altered
coal, by deposits of iron and of marble
in Algonkian rocks, themselves strait
fed, forming beds of sandstone, con-
glomerate, limestone, etc. Moreover,
the Algonkian (Huronian) strata be-
sides containing abundant carbon and
also coal gas, graphite and rocks
which will burn, have yielded frag
ments of sponges, shells, trilohites, etc,
which shows that in pre-Cambrian
times not only protozoans and sponges,
but also corals, shelled worms Gingu-
la), true worms and trilobites had
gained a foothold in the seas of that
time. In short, in the hay, dim, re-
mote ages before the Cam brian period,
the biological forces HAD gained the
victory, and the seas and even perhaps
the land masses of those times were
tenanted by comparatively highly or
ganiZed life forms. Chaos and darkness
had been succeeded by light and life,
and the very changes and vicisStudes
which were destructive to certain forms
unable to adapt themselves to such
forms and types better adapted TO such
new conditions of existence.
And so it has been ever since those
primeVal ages, of which we really know
so little The earths crust has again