Replying to LO26026 --
In this contribution I will retake the thread of At's heavy meal - LO26026
He asked us to try to go back into the past as far as possible. And as At
had written so clearly, that past could be for all of us different in
length or depth.
The present is the key to the past. A key to understand the past. But
opens this key the past to infinity?
At has asked me to expose some mindmines to you from the geological
discipline. I hesitated to do this, doubting if these examples will fit in
your mindframe and the frame of this list. The scope of this list is
broad, very broad but that does not mean that every subject fits in this
scope. The examples that I have in mind have same general implications,
also implications to learning organizations. However to see these links
and relationships an open mind is preferable. The examples could also
include some new mindmines. I hope that a warned person is able to
recognise and avoid these mines.
Geology is a science that is completely based on the present. What could
be observed now is the result of a history. A history based on
interpretations, deductions, presumptions, etc. And all this sophisticated
guess-work is the science of geology. I wonder why not all students have
chosen for such a fantastic study, where fantasy could play such an
important role. So, these observations of the present must be used as key
to the past. THE past? or A past?? Do you believe that a specific present
situation is the result of a unique and defined history? Is there only one
interpretation of the history that resulted in the present outcome?
Looking back to the growth of geology as a science we could consult the
written documents. These documents display several Mental Models (MM).
Let's not blame the persons who had these MMs, but let us learn from these
MMs.
Until circa 1700 the general picture of the MM of the Christian
interpretation of the origin of the Earth was based on the Bible. Until
then, the Bible was THE document that shaped the MM: the Earth was roughly
600 years old, especially created as home for man. And during these 6000
years the Earth has suffered from several supernatural catastrophes.
During the beginning of the 18th century some attacks on this model
happened: a heliocentric model (instead of the Earth as centre of
celestial orbits) slowly gained terrain in the MM of more and more
persons. Then in England James Hutton (1726-1797) published in 1788 his
'Theory of the Earth' and he proposed - based on numerous observations -
an important new insight: uniformitarianism. This uniformitarianism was
the articulation of tacit awareness that most probably was present within
the minds of several persons: the earth is part of several processes.
Physical, chemical, gravitational and geological processes. The Earth was
not a stable and fixed being of a creation, but it was alive. And the
supreme thought for that time was that all these processes of the present
are independant of time. They were active and identical in the past as
well. So the observation of ripple marks on the surface of a hard
sandstone could be interpreted with this insight as a beach sand with wave
action from a sea that has happened in the past. Completely comparable and
identical with observations of present beaches all over the world.
However, the MM of Hutton was not completely broken from the Biblical MM.
There were still several catastrophes in the past that interrupted all
these processes. There were so much observations that indecated these
interruptions that catastrophes are very understandable and phenomena that
are an integral part of the Earth's history. These catastrophes were still
supernatural happenings.
Later, Charles Lyell (1797-1875) build further on the frame work of Hutton
in his 'Principles of Geology'. Lyell made it even more clear that the
history of the Earth was composed of fairly long periods of continuous
geological and biological evolution (following the processes as observed
in the present), interrupted by sudden catastrophs. Lyell was the source
of inspiration of Charles Darwin. Darwin once wrote that Lyell produced a
revolution in science. Now, we could observe from documents that both
gentlemen have inspired each other. Darwin brought some nuances to the
catastrophes of Lyell. Particularly the fossil records were important
clues for both. It was already for long observed that several life forms
from the past disappeared completely. It was also often observed that some
life forms disappeared suddenly and were later 'replaced' by other
creatures. This strongly supported the catastrophic MMs. However, Darwin
has observed also that some life forms survived these sudden evolutionary
breaks and that it certainly was not the case that life on Earth has
started again and again after each catastrophic event (although after each
event on a higher level). There was some continuety observed. Lyell was
convinced of this at the end of his life.
In the rest of Europe (that part that the English used to call ' the
continent' ;-)) the idea of uniformitarianism never gained much support.
Possible because of the not so well chosen word. In France where also some
great geologists have shaped the evolution of the geological science, the
MM was somewhat different from Brittain. In France the famous George
Cuvier was in the beginning of 1800 a strong advocate of catastrophism.
This French medical doctor was also an important paleontologist. His
studies in the Paris Basin (a geological province composed of mainly
Mesosoic sedimentary rocks) on fossils convinced him again and again that
the Earth has been subjected to several catastrophes. The interrupted
succession of life forms from primitive in the past to complex towards the
present was for Cuvier a reason to think of a divine plan. This the
Biblical MM was still very important.
Back to England. In 1862 the famous William Thomson (Lord Kelvin) was the
first who seriously questioned the MM of uniformitarianism. Based on his
thermodynamic insights he concluded that it was impossible that present
processes were identical in the past. They cannot be the same because of
the gradual heat lost of the planet Earth. In the past the Earth was
hotter than now, so that fact influenced seriously all sorts of processes.
He concluded, based on his calculations on the cooling curve of the Earth
that the age of the Earth was around 100.000.000 years. At least it was
clear to him that at least the rate of processes was not the same in the
past. This age must be an enormous mental shock for a lot of persons who
were still living with the idea of the 6000 years age. A lot of MMs in
that century must have been incredably shaken and shocked. Other
calculations of the age of the Earth were based on thicknesses of
sedimentary sequences, relative ages (older/younger) and rates of
sedimantation. These calculations, and calculations based on the salinity
of ocean water came to less old ages, although much older than the 6000
yrs. Had all these people have lived in India, they would have found a
ready-made system of world chronology fully adequate for the needs of
geology at that time. According to the Hindu calender (recorded in ancient
books) the year 1800 corresponds to 1,972,948,901 since the present world
came to existence - a duration of the Earth with at least the right order.
Only a few decennia later, radioactivity was discovered. And it became
clear that from this discovery the heat production caused by the decay of
radioactive elements in the Earth's interior has seriously lowered the
cooling rate of the Earth. So already at the end of the 19th century an
older age than 100 million years came in the picture. Only a couple of
years later - in 1906 - it was Rutherford who made use of the constant
halftime of some radioactive elements to calculate the age of a single
chrystal: over 500 million years. End then things went fast. Within
another 10 years the age of the Earth became 4.6 Giga year. The Biblical
MM was smashed out of the minds. Meanwhile the fossilrecord increased too
and the beginning of life on Earth gradually shifted to older and older
ages (this is still going on).
But what happened with the catastrophic events that plagued the Earth?
Also this Biblical MM slowly disappeared in the modern minds of
scientists. Although there was and is still a large group of persons who
are creationists and catastrophists. In the late 1960's however,
catastrophic events regained popularity. The boundary betwen Cretaceous
and Tertiary (the C/T boundary) some 150 million years ago is now commonly
seen as a result of a worldwide catastrophe caused by a major impact of an
extraterrestrial object. It caused a mass extinction of 98% of all species
on Earth! The popularity of this theory is so high that lots of scientists
are searching for other clues for comparable events, much earlier. And
indeed there are at least some 'moments' in the history of the Earth were
mass extinctions are followed by an explosion of new life forms (as
happened after the C/T boundary).
Lord Kelvin was the first major scientist who questioned uniformitarianism
(present processes are idetical with processes of the past). A slight
change of this idea is actualism: modern processes give clues to processes
in the past, but are not necessarily identical. This actualism plays still
a very important role in the MMs of geologists and scientists from other
disciplines.
But slowly this actualism is loosing terrain as well. I give only some
examples:
*
the composition of the Earth's atmosphere changes dramatically from CO2
rich and oxygen depleted in the beginning (free oxygen was rapidly used
for oxidation and thus was extracted from the atmosphere). When plant life
started on Earth, free oxygen was introduced to the atmosphere by
photosynthesis. So there was a period of extensive oxidation of the
Earth's surface. About 500 million years ago animal life started. And
animals use the free oxygen and produce carbon dioxide. One can imagine
that the composition of the atmosphere has major implications for all
sorts of processes. But there is also another large difference between
present and past. That is vegetation. An Earth's surface bare and naked of
vegetation and free of bacterial activities reacts completely different to
erosional processes than a vegetated surface. Erosional processes in the
past certainly differ from the present.
*
And then there is plate tectonics, the process that plates of continental
and oceanic lithosphere move (with rates of more than 10 cm/year!) and
that oceanic crust disappear at certain places (subduction) to greater
depths. It is a process with large implications to lot of processes.
Present plate tectonics is certainly different from the past, maybe
completely other mechanisms were active in the past to cope with the heat
convection cells in the Earth's interior. Only one implication (there are
numerous) shall I mention.
The subduction of oceanic crust with oceanic sediments like carbonate
rocks, means that for very long periods (hundreds of million years) large
quantities of carbon (and thus carbon dioxide) are removed from the much
shorter carbon cycle at the surface (corbon dioxide in atmosphere ->
carbon used in life forms -> rotting -> atmosphere). Thus again, the
composition of the atmosphere is influenced, now by plate tectonics. How
was that in the past?
The MMs of lots of geologists begin to tremble and shocked. I expect in
the near future lots of new insights and changed MMs (after the two main
shocks of the last century: the age of the Earth, and plate tectonics).
Most geologists realise more and more how important it is to look as broad
as possible and holism is certainly embrased by lots of them. They call it
not holism but Gaia (the godess of earth). Unfortunately the name Gaia has
been used also by some unscientific New Age people. For those interested
in the holistic approach of earthsciences see: http://www.gaiasociety.org/
More and more scientists realise that all the processes on Earth form an
interconnected clockwork. That is why it is so extremely difficult to
understand processes like global warming and greenhouse effects. The
recent claims if ICCP that it is now proofed that recent climatic changes
are due and only due to human activities, is too simple. Apart from the
fact that it is not so interesting to judge who is guilty of this climatic
change. If after some years a new insight comes up, saying that global
warming is caused by nature itself, for instance by increased volcanic
activity; then the problem does not become less serious or less important.
A much more important question is 'how could the human race cope and adapt
to these climatic changes.
For me this whole story contains a strong lesson. MMs change and therefore
I am very careful with judgements. Another lesson for me is that the
present is a very, very complicated key to the past. For sure, the
processes of the past are different from those of the present. It is now
the time to study the evolution of processes (content). The time of
studying the evolution of forms is coming to an end.
dr. Leo D. Minnigh
l.d.minnigh@library.tudelft.nl
Library Technical University Delft
PO BOX 98, 2600 MG Delft, The Netherlands
Tel.: 31 15 2782226
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Let your thoughts meander towards a sea of ideas.
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--Leo Minnigh <l.d.minnigh@library.tudelft.nl>
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