A Snowball Earth or......?
Barry and Helen Setterfield
May 16, 2003
Some creationists argue that the entire geological
column is a construct which cannot be found on the real earth. It needs to
be stated clearly that there are four major divisions of geologic strata
which are present everywhere around the earth, and in the same order. The uppermost, or the one we
live in and on is referred to as the Cenozoic. There are three major
divisions under it, in the same order all around the world. The next
division, or era down, is the Mesozoic. The one below that is the
Paleozoic. The deepest era, or division we are aware of before we hit
basement rock is referred to as the Archaeozoic ‘era’.
Mammals, flowering plants dominant
Large reptiles, birds, palms and pines dominant
Insects, amphibians, algae, mosses, ferns dominant
Begins with Cambrian
Archaeozoic (in more detail below)
Ediacara fossils present in some areas, below which are only bacteria
Within each of these four
general eras there are a number of subdivisions. Not every place on earth has
each of the subdivisions belonging to each of the major eras, but the major
eras are always present. Where a given subdivision is present, it has the
same characteristic rock and fossil types worldwide, however.
Also world-wide is the evidence
of three separate catastrophes of major proportions separating the four major
divisions shown above.
-- Cretaceous/Tertiary Extinction
-- Permian Extinction
Earth” – or….?
Although there are many things
which can be said about the different eras and their associated catastrophes,
the one being dealt with here is the catastrophe which has been called by some
the “Snowball Earth”. This is a hypothesis attempting to explain some unusual
characteristics found in the rock formations in the upper part of the
Archaeozoic era strata around the world. The material for this paper is being
taken from the formations associated with these strata found in South
First of all, to help picture
the material being referred to later, here is a slightly more detailed chart of
the Archaeozoic strata.
Below the Cambrian Strata are the "Precambrian" or Proterazoic
'eras'. The top two major divisions, the Marinoan and the Sturtian are the areas which have
given rise to the theory of an earlier "Snowball Earth".
||"Cambrian explosion" of fossils, mainly limestones and sandstones
In a few places around the world there is an extra strata here containing the Ediacaran fossils
"upper glacial sequence"
Nucaleena Formation – dolomite (a kind of
Elatina Formation – includes Reynella siltstone (finely-layered,
red-colored sediments with dropstones embedded)
and Whyalla sandstone, as well as other slates and quartzites.
Purple, gray, and green slates and shales
"lower glacial sequence"
Brighton limestone – a carbonate capping to the rest of the Sturtian sequence below.
Tapley Hill Formation – finely laminated siltstone
Diamictites -- debris of various sorts and
sizes of rock in a cement-like matrix
Belair subgroup quartzites, slates, and shales
Dolomites – a sort of limestone
Geologists have become very aware of a suite of rocks
that occurs almost worldwide near the Proterozoic/Cambrian boundary. The
designation of this grouping of rocks is sometimes given as the
Infra-Cambrian or, more often, as the Neo-Proterozoic. On the atomic or
radiometric timescale used by geologists, these strata date from around
750 million atomic years down to something less than 600 million atomic
years. The strata shown in this article all come from the southern suburbs
of Adelaide, South Australia. This area is known as one of the
type-sections showing the strata at this level, as evidenced by the fact
that both the Sturtian and Marinoan sequences get their names from this
part of Australia even though they are found around the world. The photographs in Part 1 are of rocks that
are all dated towards the higher end of this timescale, while the photos
from Part 2 are from the lower end.
In the first major sequence below the Cambrian, there
are finely layered strata containing something called dropstones.
These stones were somehow 'dropped' into the strata, causing interruptions
or small deformations in the steady series of lines which indicate the
layers of strata. One way we know this can happen is through the
movement of glaciers. Glaciers will pick up material and, as they
recede during a melt, will drop material, including rocks, into the mud it
is leaving behind. So when these dropstones were found in strata
that deep, one of the first suspicions was perhaps a glacier did this.
Something else caused many to wonder about some kind
of large glaciation all over the earth's surface when stones found in the
Flinders Ranges north of Adelaide in South Australia showed up with
paleomagnetic readings indicating they originated at the equator.
One would not suspect to find a lot of material which originated at the
equator in South Australia. Did ice do this?
The third bit of evidence that started some thinking
very strongly about the possibility of an ice-covered world was finding
something called 'diamictites' even below the sequences which contained
the dropstones. Diamictites are what we refer to as a cement-like
matrix of material which contains rocks of all different sizes and shapes
embedded within it. "A debris layer" is a good description of the
kind of material it reminds one of.
The dropstones, the paleomagnetic indications, and
the diamictites all together have given rise to a theory referred to as
the "Snowball Earth" theory. Knowing that there is almost nothing
which could result in all three of these things showing up as we go
through the layers of the earth, there has been a fairly strong case
presented for the possibility that the entire earth was once covered in
ice. It would have to be the entire earth, for if there were
glaciers at the equator which could recede to the south, carrying
equatorial rocks to Australia, then there must have been glaciers
everywhere. What else besides glaciers could have done this?
There is something else, and that is what all this is about.
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