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 special -ordinator of the INTAS project on Geomagnetism and Climate (1998-20 Head of Paleogeophysics & Geodynamics at Stockholm University, Swede [email protected]www.pog.nu
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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
November 2000: 1 month reseach/expeditionNorth Male, Guidhoo, Baa and Raa Atolls
Mörner, J.& F. Laborel, S. Dawson, S. Islam, et al.
February 2001: ”reef woman” investigationMörner, Tooley
November 2001: 1 month research/expeditionAddu, 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 researchLaamu, Guidhoo, Viligili Atolls
Mörner, S. Dawson, B. Lembke
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 during LGM and the subsequent periods
Nils-Axel Mörner
SeaLevel Changes in the last 130,000 years
THE MALDIVES:
No subsidence
No flooding
Just normal
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 todayimplying that
