Transcript Document

THE MALDIVES PROJECT IN THE INDIAN OCEAN
MULTIPLE INTERACTING PARAMETERS
Nils-Axel Mörner
.
President (1999-2003) of the INQUA Commission on
Sea Level Changes and Coastal Evolution
Leader of the Maldives Project (from 2000 on);
an international research project among sea level specialists
Co-ordinator of the INTAS project on Geomagnetism and Climate (1998-2003)
Head of Paleogeophysics & Geodynamics at Stockholm University, Sweden
[email protected]
www.pog.nu
Some
1200
islands
Welcome to the Maldives
Grouped
in
some 20
larger
atolls
The Maldives International Sea Level Project
March 2000: setting up the project
Mörner
November 2000: 1 month reseach/expedition
North Male, Guidhoo, Baa and Raa Atolls
Mörner, J.& F. Laborel, S. Dawson, S. Islam, et al.
February 2001: ”reef woman” investigation
Mörner, Tooley
November 2001: 1 month research/expedition
Addu, Foammulah, North Male, Guidhoo, Baa Atolls
Mörner, J. & F. Laborel, Tooley, Collina, Allison, et al.
December 2003: ”Doomsday called off” (TV)
Mörner, Mortensen, Petersen
February 2005: post-tsunami research
Laamu, Guidhoo, Viligili Atolls
Mörner, S. Dawson, B. Lembke
The Maldives during LGM and the subsequent periods
Nils-Axel Mörner
The Maldives, is a group of about 1200 small atoll islands grouped in about 20 larger atolls.
The Holocene reefs seem largely to be a thin apron upon older reef bodies (>40,000 BP).
The atolls are surrounded by shore-marks from the LGM low-stand and several subsequent
sea levels from a punctuated sea level rise.
The old reef structures, exposed for sub-aerial weathering during lower sea level stands,
are extensively karstified with systems of submarine caves.
This calls for a completely new history of the islands not only with respect to sea level changes
but primarily with respect to their environmental conditions during LGM to Younger Dryas.
The post-LGM sea level rise was rapid but punctuated by a number of steps (submarine shores).
At 4000 BP, the present sea level was reached. It was followed by a series of rapid sea level
oscillations up to the present (our new sea level curve). Six paleo-tsunami events are recorded.
THE MALDIVES:
No subsidence
No flooding
Just normal
SeaLevel Changes in the last 130,000 years
At LGM (~20 ka), sea level was at about –150 m, indicating that the geoid trough was
even deeper then. The Maldives now consisted of 20 large islands, around their edges
being surrounded by reef “chimneys” of about 150 m height and with a flat inland
depression at around 100 m above sea level. Climate was warm and wet judging from
the strong karstification. The inland depressions must have been crossed by river
systems and covered by a dense rainforest. Surely many land animals and birds lived
in the forest; but which ones, we have no records of at present. The strong karts
weathering contributed to the global carbon budget.
There is a prominent sea level halt with deltas and shore cuts at around –65-70
m. This may represent the Younger Dryas period. The inland lowlands, now
only some 10-20 m above sea level, were crossed by rivers debouching between
the coastal rim of reef “chimneys”, now about 60-70 m high. The environment
must have changed significantly. But rain forests may still persist.
After this stage, sea level rose rapidly with some consistent levels of distinct
marks of more stationary sea level positions. When the inland basins were
flooded, flora and fauna diminished drastically and only the coastal
“chimneys” remained above sea level. Time ~9000 C14 yrs BP.
Finally, today, there remain some 1200 islands
primarily formed by coral rubble and coral sand.
The new sea level curve of the Maldives; present level reached ~4000 BP, sea
level strongly oscillating for regional dynamic reasons, a drop in sea level
~1970, no rise in the last 30 years.
Example of records of short high sea levels.
This coral, today 5-10 cm above mean zero,
and “in situ” requites a water depth of ~60
cm (according to Laborel), implying a
higher sea level of about +70 cm.
The coral is cut and dated
at 2 levels.
(2) = 1585 +35 BP
(1) = 1635 +35 BP
Sea level oscillations in the last millennium (cores from two fens)
The 2 swamps became lakes in ~1790 and both dried up in ~1970
NB. Peat and shell dates differ by 350 years, a good measure of the local “sea correction”
Queen’s Bath
(4) +0.6 m ~400 BP
(3) +20-30 cm >1970
(2) Present HTL
(1) Present MTL
The higher ”pre-1970 shore” is recorded in a map of 1922.
At ~1970
Sea Level fell some 20 cm
Causing erosion
with sand deposition
outward, downward
Leaving an old fossil shore and
an old owergrewing surface of
grey weathered corals.
The present shore
has remained stable
for ~30 years
This is our Maldives story up to today
“The Maldives Sea Level Research Project”
originally by the INQUA Commission on “Sea Level Changes and Coastal Evolution”
The most important conclusions are:
the -150 m LGM level with strong karst weathering
and likely rain forests in the inland areas
and
the total absence of any on-going sea level rise today
implying that
“the flooding concept must be called off”
Today I launch a short book
entitled:
The Greatest Lie Ever Told
unfortunately I have to charge
15 Australian dollars for it