study of landforms – geomorphology – between the
1880s and 1930s.
Davis and Coral Reefs
William Morris Davis (1850–1934) was the dominant figure in the development and codification of geomorphology (the science of the study of landforms and
the processes that form them) from the last decades of
the nineteenth century, responsible for the concept of the
“cycle of erosion” whereby landforms pass progressively,
irreversibly, and predictably through the stages of
“youth”, “maturity”, and “old age”. Following his resignation from the Sturgis Hooper Professor of Geology at
Harvard University in 1912 (where he was succeeded by
R. A. Daly), his scientific focus became strongly reefbased; he published over 50 items on coral reefs between
1913 and 1934, including a major treatise, ‘The Coral Reef
Problem’, published in 1928. Much of this work was deskbased and theoretical, but he undertook a 9 month cruise to
Pacific reefs in 1914 (including visits to Hawaii, Fiji, New
Caledonia, the New Hebrides, New Caledonia, and the
Great Barrier Reef (where a visit to Green Island, Great
Barrier Reef was dismissed as “an entertaining experience, but, as might have been expected, entirely fruitless
as far as the origin of the reef is concerned” (Davis,
1928, p. 347)), Rarotonga and Tahiti) and a shorter visit
to the Caribbean in 1923. He was totally supportive of
Darwin’s subsidence theory, promoted J. D. Dana’s “principle” of the importance of the embayed shorelines as evidence for volcanic island subsidence and made useful
observations on the cliffs of volcanic islands on the margins of the reef seas, which he attributed to a lack of reefal
protection during glacial stages. As P. B. King perceptively pointed out (see King and Schumm, 1980), his analysis had most conviction when dealing with the relatively
simple tectonic settings of oceanic reefs but struggled elsewhere. Thus, as Stoddart (1994) has argued, he systematically misrepresented the geomorphic history of elevated
reef islands in Fiji, Tonga, the Loyalty Islands and the
southern Cook Islands, from no or very limited field
observations, erroneous assumptions on erosion rates
and the removal of limestone topography, and by ignoring
paleontological evidence for the antiquity of exposed
raised limestones.
Bibliography
Chorley, R. J., Beckinsale, R. P., and Dunn, A. J., 1973. The History
of the Study of Landforms or the Development of Geomorphology. Volume 2. The Life and Work of William Morris Davis.
London: Methuen.
Davis, W. M., 1928. The Coral Reef Problem. New York: American
Geographical Society (Special Publication No. 9).
King, P. B., and Schumm, S. A., 1980. The Physical Geography
(Geomorphology) of William Morris Davis. Norwich: Geo
Books.
Stoddart, D. R., 1994. Theory and reality: The success and failure of
the deductive method in coral reef studies – Darwin to Davis.
Earth Sciences History, 13, 21–34.
Cross-references
Daly, Reginald Aldworth (1871–1957)
Dana, James Dwight (1813–1895)
Darwin, Charles (1809–1882)
Stoddart, David Ross (1937–)
Subsidence Hypothesis of Reef Development
DENSITY AND POROSITY: INFLUENCE ON REEF
ACCRETION RATES
David Hopley
James Cook University, Townsville, QLD, Australia
Estimations of coral reef accretion rates can be undertaken using a number of techniques. Most tedious is
the use of growth rates from individual organisms
(Chave et al., 1972). More recent methods include the
measurement of total reef metabolism and calcification
(Kinsey, 1985) or estimates of rates during the Holocene
from dated drill cores (Davies, 1983; Davies and
Hopley, 1983).
Alkalinity anomaly measurements can be made for
different zones of the reef. However, in transforming
results, from kg m
2 /year into vertical accretion rates, differences in specific gravity (S.G.) of different elements
of the reef need to be considered. Elements such as
corals, molluscs, codiaceans and Halimeda are composed of aragonite (S.G 2.94) while coralline algae,
foraminifera and bryozoans are mainly magnesium calcite (S.G 2.72).
Producing even greater variability in the conversion is
the porosity of the reefal fabric. Coral colonies have bulk
densities of 1.0–2.2 g/cm
3
, (Buddemeir et al., 1974).
The reef fabric in drill cores has a wide range of porosities
from very low (where internal cavities have been infilled
with marine cements) to very high, in branching coral
framework. Nonetheless, the results from drill cores are
remarkably similar to those obtained from reef metabolism studies, where a porosity value of 50% is normally
assumed, (Smith, 1983).
Vertical accretion rates (Figure 1) vary up to 16 m/
1,000 years with the mode around 7–8 m/1,000 years
obtained from both alkalinity studies and drill cores. Reef
fabric porosity plays an important role in both framework
and detrital deposition. Higher rates in framework are
mainly from open branching corals, lower rates from head
corals and algal crusts. Within detrital facies two distinct
groupings occur:
(a) 1–9 m/1,000 years representing steady, mainly
fine grained accumulation during normal stormy
weather.
(b) Extremely high rates of 13–18 m/1,000 years from
coarser more porous gravel sheets deposited during
short periods of cyclonic weather.
DENSITY AND POROSITY: INFLUENCE ON REEF ACCRETION RATES
303
1880s and 1930s.
Davis and Coral Reefs
William Morris Davis (1850–1934) was the dominant figure in the development and codification of geomorphology (the science of the study of landforms and
the processes that form them) from the last decades of
the nineteenth century, responsible for the concept of the
“cycle of erosion” whereby landforms pass progressively,
irreversibly, and predictably through the stages of
“youth”, “maturity”, and “old age”. Following his resignation from the Sturgis Hooper Professor of Geology at
Harvard University in 1912 (where he was succeeded by
R. A. Daly), his scientific focus became strongly reefbased; he published over 50 items on coral reefs between
1913 and 1934, including a major treatise, ‘The Coral Reef
Problem’, published in 1928. Much of this work was deskbased and theoretical, but he undertook a 9 month cruise to
Pacific reefs in 1914 (including visits to Hawaii, Fiji, New
Caledonia, the New Hebrides, New Caledonia, and the
Great Barrier Reef (where a visit to Green Island, Great
Barrier Reef was dismissed as “an entertaining experience, but, as might have been expected, entirely fruitless
as far as the origin of the reef is concerned” (Davis,
1928, p. 347)), Rarotonga and Tahiti) and a shorter visit
to the Caribbean in 1923. He was totally supportive of
Darwin’s subsidence theory, promoted J. D. Dana’s “principle” of the importance of the embayed shorelines as evidence for volcanic island subsidence and made useful
observations on the cliffs of volcanic islands on the margins of the reef seas, which he attributed to a lack of reefal
protection during glacial stages. As P. B. King perceptively pointed out (see King and Schumm, 1980), his analysis had most conviction when dealing with the relatively
simple tectonic settings of oceanic reefs but struggled elsewhere. Thus, as Stoddart (1994) has argued, he systematically misrepresented the geomorphic history of elevated
reef islands in Fiji, Tonga, the Loyalty Islands and the
southern Cook Islands, from no or very limited field
observations, erroneous assumptions on erosion rates
and the removal of limestone topography, and by ignoring
paleontological evidence for the antiquity of exposed
raised limestones.
Bibliography
Chorley, R. J., Beckinsale, R. P., and Dunn, A. J., 1973. The History
of the Study of Landforms or the Development of Geomorphology. Volume 2. The Life and Work of William Morris Davis.
London: Methuen.
Davis, W. M., 1928. The Coral Reef Problem. New York: American
Geographical Society (Special Publication No. 9).
King, P. B., and Schumm, S. A., 1980. The Physical Geography
(Geomorphology) of William Morris Davis. Norwich: Geo
Books.
Stoddart, D. R., 1994. Theory and reality: The success and failure of
the deductive method in coral reef studies – Darwin to Davis.
Earth Sciences History, 13, 21–34.
Cross-references
Daly, Reginald Aldworth (1871–1957)
Dana, James Dwight (1813–1895)
Darwin, Charles (1809–1882)
Stoddart, David Ross (1937–)
Subsidence Hypothesis of Reef Development
DENSITY AND POROSITY: INFLUENCE ON REEF
ACCRETION RATES
David Hopley
James Cook University, Townsville, QLD, Australia
Estimations of coral reef accretion rates can be undertaken using a number of techniques. Most tedious is
the use of growth rates from individual organisms
(Chave et al., 1972). More recent methods include the
measurement of total reef metabolism and calcification
(Kinsey, 1985) or estimates of rates during the Holocene
from dated drill cores (Davies, 1983; Davies and
Hopley, 1983).
Alkalinity anomaly measurements can be made for
different zones of the reef. However, in transforming
results, from kg m
2 /year into vertical accretion rates, differences in specific gravity (S.G.) of different elements
of the reef need to be considered. Elements such as
corals, molluscs, codiaceans and Halimeda are composed of aragonite (S.G 2.94) while coralline algae,
foraminifera and bryozoans are mainly magnesium calcite (S.G 2.72).
Producing even greater variability in the conversion is
the porosity of the reefal fabric. Coral colonies have bulk
densities of 1.0–2.2 g/cm
3
, (Buddemeir et al., 1974).
The reef fabric in drill cores has a wide range of porosities
from very low (where internal cavities have been infilled
with marine cements) to very high, in branching coral
framework. Nonetheless, the results from drill cores are
remarkably similar to those obtained from reef metabolism studies, where a porosity value of 50% is normally
assumed, (Smith, 1983).
Vertical accretion rates (Figure 1) vary up to 16 m/
1,000 years with the mode around 7–8 m/1,000 years
obtained from both alkalinity studies and drill cores. Reef
fabric porosity plays an important role in both framework
and detrital deposition. Higher rates in framework are
mainly from open branching corals, lower rates from head
corals and algal crusts. Within detrital facies two distinct
groupings occur:
(a) 1–9 m/1,000 years representing steady, mainly
fine grained accumulation during normal stormy
weather.
(b) Extremely high rates of 13–18 m/1,000 years from
coarser more porous gravel sheets deposited during
short periods of cyclonic weather.
DENSITY AND POROSITY: INFLUENCE ON REEF ACCRETION RATES
303