Sandy stripes
Do many layers mean many years?
by Don Batten
Early one morning in August 1995, I went surfing with my son at Greenmount Beach
on the Gold Coast, QueensIand Australia. I took my camera just in case anything
interesting would tempt me to finish off the loaded film. Walking along the beach,
noticed where the high tide and waves during the night had eroded sand from the
beach (Photo 1). To my surprise I saw what looked like clear laminations, or layering,
in the sand—formed by the separation of normal silica sand-grains and smaller,
denser mineral sand-grains such as rutile, which are dark in colour (Photo 2). The
layering was present along the whole sand mass exposed.
Photo 1. The cliff scarp on Coolangatta Beach, formed by a storm
surge.
Layers which look similar to these are often believed to be evidence for huge periods
of time. For example, they may be interpreted as being the result of periodic floods
depositing material. In some rocks there are pairs of dark and light layers which
are regarded as the material deposited in annual floods. In such a concept, material
is washed into settles slowly to the bottom, the fine material settling after the
coarse, giving one pair of bands of fine and coarse material for each flood. If
it happened this way, and there are thousands of laminations, this would represent
thousands of years of floods. Using this sort of reasoning, rocks are sometimes
assigned ages of many millions of years.
However, many laminations have been found to form quite rapidly—within a few
hours on June 12, 1980—in mud/ash flows following the Mount St Helens eruption
in Washington state in the North-west of the United States.1 Also, the
experiments of Pierre Julian, Yongqiang Lan and Guy Berthault using flow tanks showed
how, with a mixture of sand particles of different sizes and densities, many laminations
can form almost instantaneously in rapidly flowing water.2 The type of
lamination—whether it was fine on coarse or coarse on fine—depended
on the relative density and size of the particles.
Some detective work
How did the sand on the beach come to be laminated? Beach sand is not often layered
like this. This sand had been put there recently in a beach restoration project
of the Gold Coast City Council. The beaches along this part of the coast lose sand,
apparently because of breakwaters built to protect the Tweed River mouth for shipping
purposes. These breakwaters stop the natural drift of sand northward to the Gold
Coast beaches, which occurs because of prevailing ocean currents. When the supply
of sand from the south is impeded, sand lost is not replaced so the beaches lose
sand—which is not good for the beaches or the tourism industry.
Photo 2. Laminations in the cliff scarp sand. The height is about
650 mm (2 feet).
The beach restoration project involved the dredging of sand from the sand bar in
the Tweed River and carrying it by ship several kilometres north to the southern
Gold Coast beaches, where it was pumped ashore as a water/sand slurry through a
large pipe to the beach. As the sand was restored to one section of beach, the pipe
was extended by sections to supply sand to the next section of beach (see diagram
below: shows plan view of ship, pipe to beach and slurry discharge on beach).
According to Dr Tom Conner of Kinhill, Cameron and McNamara, the engineering company
which managed the project, the ship carried 8,000 cubic metres of sand at a time.
It took only an hour to pump the sand to the beach in a slurry of approximately
30 per cent sand and 70 per cent water. This amounts to over 400,000 litres of water
and sand (equivalent to about 10 private swimming pools of water) per minute. This
created what Dr Conner described as quite a fast flowing little ‘river’
back towards the sea, with the sand being deposited as the water flowed. In other
words, the sand was deposited in quite a fast-flowing, turbulent environment. The
amount of sand pumped in one hour is enough to cover a football field to well over
a metre deep. The sections in the photographs would have been formed in less than
an hour, since the area covered at one time was much less than a football field
in size.
Guy Berthault and his co-workers, in their controlled experiments in flow tanks,
were able to obtain layering like this using particles with different sizes—here,
they were different densities, as well as different sizes. It appears that there
are different ways to get many alternating bands of layering rapidly, without millions
of years.
In fact, many evolutionist geologists would themselves acknowledge this, if pressed.
In any case, the idea that thousands of perfectly formed laminations can form slowly
and gradually has other problems. For example, how does a lamination on a lake bottom
from a flood remain undisturbed for many months until the next flood comes to deposit
the next lamination? One would expect that biological activity and even mild currents
would disturb the neat laminations, which, in the Green River Formation in the United
States, for example, average only about 0.1 millimetre thick. Each such thin lamination
is supposed to have remained undisturbed for about a year before the next influx
of sediment was deposited on top. Also, there are many fish beautifully preserved
as fossils in the Green River rocks—how could this happen with a mere 0.1
millimetre per year of sediment being deposited? There is now ample evidence that
fine layering and laminations can form rapidly in flowing water—in the sorts
of conditions that one could expect during various phases of the biblical Flood.3
How it’s done
References and footnotes
- Ken Ham, I got excited at Mount St. Helens!, Creation
, 15(3):4–19, June 1993.
- Pierre Julien, Yongqiang Lan and guy Berhault, Experiments
on stratification of heterogenous sand mixtures, Journal of Creation, 8(1):37–50,
1994.
- Strictly speaking, true laminations require desiccation (drying) planes between
layers, which are not present here—yet. Also, some of the patterns in this
beach example merge, as they do in some sandstones (sand which, under right conditions,
has dried and hardened). The Berthault example (Ref. 2) is thus more potent for
the formation of true laminations than that shown here.
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