teaching - Earth Science Teachers' Association

TEACHING EARTH SCIENCES ● Volume 31 ● Number 4, 2006
Reviews
Inventing the Earth: ideas on Landscape Development Since 1740. by Barbara A.Kennedy.
Blackwell Publishing Ltd. Oxford, 2006. 160pp. ISBN-13: 978-1-4051-0187-5 (Hardback),
ISBN-10: 1-4051-0188-1(Paperback)
In her Preface the author stresses that
this is not a text-book on the History
of Earth Science, but rather forms a
series of essays giving a personal
impression of the importance of key
episodes in the development of
geomorphology within an Anglo-
American perspective. Much of the
material is drawn from lectures,
seminars and tutorials given in the
Universities of Manchester and Oxford
towards the end of the twentieth century.
Nearly one third of the 126 pages of
text is devoted to examination of the
precepts by which scientific paradigms
are tested, exploring the impacts of the
Ruling Hypothesis and the Method of
Multiple Working Hypotheses. She
identifies four key constraints under
which the emerging eighteenth century
geomorphologists were forced to work.
First that the Bible contained Divine
Authority, second that the time
framework since creation as calculated
by Ussher was very limited, third that
the only major change to the Earth’s
surface since creation was due to the
divinely inspired Noachian flood of
2348BC, and fourth that the Almighty
followed the laws of Newtonian
mechanics.
After Buffon (1749) was heavily
criticized by theologians for stating that
there was a need for an increased
timescale to permit landscape
development, it was not until the work
of Hutton (1785) and later Playfair
(1805) who demanded indefinite time
scale to permit lithification, erosion and
later tilting before further burial by
sediments to allow for the development
of unconformities. Although initially
disputed by Cuvier and Lyell,the latter
came to recognise to need for vast
periods of time to allow many observed
phenomena to develop. Interestingly
Darwin (1859) entered the fray,
estimating the need for the passage of
300Ma for formation of the topography
of the Weald. Later Holmes (1913)
estimated the need for 2000Ma and the
latest figure of 4550Ma is from Patterson
(1953).
The third chapter is devoted to the
influence of Lyell on developing
acceptable ‘modern’ scientific methods
of assessing the main elements of
geology in the nineteenth century.
To the British geologist/
geopmorphologist the in-depth
assessment of the contributions of
French, German, Italian and Swiss
workers gives a welcome historical
context, for any advances in the science
must be seen within the framework of
knowledge of the time. Conflicting
views of the presence of polymict gravels
between lava flows and their relationship
to the biblical deluge or repeated
catastrophic events are presented with
valuable comments. The need for
mechanisms to produce landforms and
their distributions is introduced with
questions such as ‘Are the highest
mountains the oldest or the youngest?’
Kennedy points out development of
concepts through the eleven editions of
Lyell’s Principles of Geology which provide
insights into active processes. Although
essentially uniformitarian at heart, Lyell
collected evidence of earthquake impacts
and sea-level changes as at Serapis. It is
instructive to learn that Lyell not only
identified that climate change in one area
was accompanied by climate change
elsewhere, but also believed that the
distribution of mountain ranges also
exerted some controls on climate.
The fourth chapter opens with a list
of factors by which Huttonian concepts
failed to satisfy conditions in many
upland areas. In the Alps both
Charpentier and Saussure had identified
such problems before Agassiz provided
his comprehensive analysis of glacial
phenomena, suggesting interpretations
which Lyell initially found difficult to
accept, but later espoused.
The fifth chapter addresses advances
resulting from the increasing possibility
of scientists taking part in the major
exploratory expeditions, of which
Darwin on the Beagle is perhaps the
most familiar example. Although armed
with a copy of Lyell, Darwin made his
own observations of geomorphological
processes and products in many areas.
His original contributions in the study of
coral reefs, volcanic islands, and
extensive geological observations along
the coasts of south America have been
highly praised. His genius would have
been recognised for those works alone
irrespective of his evolutionary concepts.
It took over 180 years of investigation
before it was accepted that rain and
rivers are important in earth sculpture,
with wind, ice and the sea playing minor
or local supporting roles on landscape
development. Outside Europe, until the
end of the American Civil War, virtually
only the landscapes of the north and
north-east of America had been
examined. From his observations on the
U.S. Government Expedition of 1838-43
Dana believed that all major river
systems were post-Tertiary in origin,
largely on the basis of rapid fluvial
incision into Pacific volcanic islands.
In terms of landscape development
Kennedy identifies the problem facing
these geomorphologists, namely how a
narrow gorge or steep-sided valley could
open up to a shallow cross-section with
gently inclined slopes. It was the
pioneering work of Powell in the Grand
Canyon which showed the connection
between vertical and horizontal
denudation. His inspirational
recognition of the base level concept
linked uplift to valley development and
the role of tectonism in stimulating
subaerial denudation. Elevation above
base level, induration of the rocks, and
the amount of rainfall were identified as
principal factors, with vegetation cover a
further contributor. Like Gilbert, later,
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