The eustatic sea level is the distance from the center of the earth to the sea surface. Eustatic changes refer to global variations in sea level. Eustatic changes can occur on a range of timescales, from decades to millions of years. Understanding the causes and effects of eustatic changes is important for predicting and mitigating the impacts of future sea level changes. One of the primary drivers of eustatic changes over geological time scales is the growth and retreat of ice sheets. Changes in the eustatic sea level lead to changes in accommodation.

1. ASSAM UNIVERSITY, SILCHAR
Department of Earth science
Eustatic changes with special reference to quaternary
period
Presented By-
SONIYA GHOSH
NIPEN SINGH
KUKI MONJORI BORUAH
BEDANTO CHUTIA
BRISTISHIKHA BURAGOHAIN
Under the Guidance of
Dr. URBASHI SARKAR

2. CONTENT
INTRODUCTION
EUSTATIC THROUGHOUT THE GEOLOGICAL TIME
CAUSES OF EUSTATIC CHANGES IN QUATERNARY PERIOD
GLACIAL-INTERGLACIAL CYCLE INFLUENCING EUSTATIC CHANGES IN
QUATERNARY
ANTHROPOGENIC IMPACT ON EUSTATIC CHANGES
QUATERNARY EUSTATIC CHANGES IN INDIA
CONCLUSION
REFERENCES

3. INTRODUCTION
 The eustatic sea level is the distance from the center
of the earth to the sea surface.
 Eustatic changes refer to global variations in sea
level.
 Eustatic changes can occur on a range of
timescales, from decades to millions of years.
 Understanding the causes and effects of eustatic
changes is important for predicting and mitigating the
impacts of future sea level changes.
 One of the primary drivers of eustatic changes over
geological time scales is the growth and retreat of ice
sheets.
 Changes in the eustatic sea level lead to changes in
accommodation.

4. EUSTATIC CHANGES THROUGHOUT THE GEOLOGICAL TIME
PALEOZOIC ERA
The most significant occurred during the
Ordovician Period, sea level rose to the
highest level.
During the Devonian Period, around 380
million years ago, dropping of sea level took
place.
PRECAMBRIAN
At least three significant eustatic event.
The first occurred around 2.3 billion years
ago when the first large-scale glaciation took
place.
The second event occurred around 1.8 billion
years ago
The third event occurred around 600 million
years ago.

5. MESOZOIC ERA
One of the most significant rises
occurred during the Jurassic period,
when sea levels were about 200 meters
higher than they are today.
During the Cretaceous period, sea level
drops
CENOZOIC ERA
During the Eocene epoch, around 50 million
years ago, sea levels were again very high .
During the Oligocene Epoch, around 30
million years ago, sea levels dropped
significantly.
Finally, during the Pleistocene Epoch,
around 2.6 million years ago, sea levels
fluctuated dramatically due to the repeated
cycles of glaciation and deglaciation that
occurred during this time.

7. CAUSES OF EUSTATIC CHANGES IN
QUATERNARY
1.GLACIO-EUSTASY
 A CHANGE IN SEA LEVEL DUE TO THE
UPTAKE OR RELEASE OF WATER FROM
GLACIERS AND POLAR ICE.
 TODAY, THE ONGOING PROCESS OF
GLACIO-EUSTASY IS CONTRIBUTING TO
THE CURRENT TREND OF RISING SEA
LEVELS , AS MELTINNG GLACIERS AND ICE
SHEETS RELEASE WATER INTO THE
OCEAN.
2.ISOSTASY
 EUSTATIC CHANGES DURING THE
QUATERNARY PERIOD BECAUSE THE
RISE AND FALL OF LAND MASSES DUE
TO ISOSTATIC ADJUSTMENTS.
 CAN CAUSE CHANGES IN THE VOLUME
OF WATER IN THE OCEAN .
 FOR EG. , DURING GLACIAL PERIOD ,
LARGE ICE SHEETS FORM ON LAND
,WHICH CAUSES THE LAND TO DEPRESS
AND SEA LEVEL TO DROP.

8. WHEN WATER IS ADDED TO THE
OCEAN , THE WEIGHT OF THE WATER
INCREASES, CAUSING SEA FLOOR TO
SINK , RELATIVE SEA LEVEL RISE.
4.HYDRO ISOSTASY AND RELATIVE SEA
LEVEL CHANGES
 Glacial isostasy is the process by which land masses that were depressed
or uplift due to the weight of ice sheets during glacial period slowly rebound
and readjust after the ice melts.
 It can also causes differences in relative sea level between different
regions.This can lead to variations in sea level rise and fall along coastlines.

9.  Different region of the earths surface exhibit different response to changes
in the earths gravity field , due to variations in the mass distribution of
the earths interior and its surface.
 Eg., equatorial ocean siphoning , phenomenon that occurs in the
equatorial region where the ocean is shallower and earths rotation
causes a centrifugal force that creats a slight bulge in the ocean surface.
 Equatorial ocean siphoning can have important implication for sea level
and ocean circulation patterns around the world.
6.GLOBAL VARIATION IN GEOPHYSICALl RESPONCE AND
EQUATORIAL OCEAN SIPHONING
• The Earth is not a perfect sphere.
• The melting of the glaciers and ice sheets , causes a redistribution of
mass on the earth’s surface , which can causes the geoid to shift and
change shape.
• Because the melting of ice sheets leads to a transfer of water from land
to ocean , causing a shift in the oceans mass distribution and altring the
shape geoid.
5.THE GEOID AND CHANGES ITS CONFIGURATION

10. GLACIALINTERGLACIAL CYCLE INFLUENCING EUSTATIC CHANGES IN
QUATERNARY
 The quaternary period is characterized by a series of glacial and interglacial cycles that have
had a profound impact on eustatic sea level changes.
 The glacial-interglacial cycles of the quaternary period have had a significant impact on the
earth's geography and ecosystems.
 The glacial period that peaked 21,500 years ago was only the most recent of five glacial
periods in the last 450,000 years. In fact, the earth system has alternated between glacial and
interglacial regimes for more than two million years, a period of time known as the
Pleistocene.
 The duration and severity of the glacial periods increased during this period, with a particularly
sharp change occurring between 900,000 and 600,000 years ago. Earth is currently within the
most recent interglacial period, which started 11,700 years ago and is commonly known as the
Holocene epoch.

11. THE LAST GLACIAL MAXIMUM (LGM)
 The last glacial maximum (LGM) occurred about 20,000 years ago, during the last phase of the
Pleistocene epoch. At that time, global sea level was more than 400 feet lower than it is today,
and glaciers covered approximately:
8% of earth’s surface
25% of earth’s land area
33% of Alaska
 Beginning about 15,000 years ago, continental glaciers retreated and sea level began to rise.
Sea level reached its current height about 8,000 years ago and has fluctuated ever since.
 Today, glaciers cover approximately:
3% of earth’s surface
11% of earth’s land area
5% of alaska.

12. THE LAST GLACIAL MAXIMUM DEFINED
 The last glacial maximum (LG) represents the latest phase in earth's recent geological history
when the planet's average temperature reached a minimum and the area of land covered by
Glaciers and ice sheets reached a maximum.
 During the LGM, (between 26,000 and 18,000 years ago), there was about three times More
glacier ice on the planet than there is now.

13. POST GLACIAL REBOUND
Due to eustatic sea level change over the past
20,000 years, there has been approximately 125 m of
eustatic sea level rise due to glacial melting. Most of
that took place between 15,000 and 7,500 years ago
during the major melting phase of the north American
and Eurasian ice sheets (fig). At around 7,500 years
ago, the rate of glacial melting and sea level rise
decreased dramatically, and since that time, the
average rate has been in the order of 0.7 mm/year.
The Sea level rise resulting
from the melting of glacial ice
over the past 24000 years .

14. ANTHROPOGENICIMPACTON EUSTATIC CHANGES IN QUATERNARY
PERIOD
 MELTING OF GLACIERS AND ICE CAPS
Human activities; burning fossil fuels.
Increases atmospheric concentration of
greenhouse gases.
Changes in ocean circulation pattern.
Leads to direct impact on sea level.
 LAND USE CHANGES
Conversion of natural ecosystems, such as forests and wetlands to
agricultural/urban land and industrial purposes.
Leads to increased erosion & sedimentation.
Which can alter the shape and volume of river channels and
estuaries.
In turn, these changes can impact sea levels by affecting the flow of
water from rivers into the ocean.

15.  GROUNDWATER DEPLETION
 Excessive use of groundwater for irrigation, drinking water, and
industrial purposes, often at rates that exceed the rate of natural
recharge.
 Results declines in groundwater level in many regions,
particularly In area with high population density and intensive
agriculture
 Weight of overlying land decreases, which can cause land
subsidence and, in some cases, lead to a relative increase in sea
level.
 RESERVOIR CONSTRUCTION
 For hydroelectric power generation or water supply Reservoirs
can store large volumes of water, which can lead to changes in
the distribution of water across the earth's surface.
 Evaporation from reservoirs increases in atmospheric moisture
which lead to changes in precipitation patterns and contribute to
eustatic changes.

16.  COASTAL DEVELOPMENT
Development for human habitation and industry can alter the shape & volume of estuaries, increase
sedimentation rates leads to destruction of coastal wetlands and other natural ecosystem can also exacerbate
the impacts of sea level rise by increasing the vulnerability of coastal communities to flooding and erosion.

17. QUATERNARY EUSTATIC CHANGES IN INDIA
 Available data for the early Pleistocene sea level along the west coast indicate that around
220,000 years before present (BP) the sea level was higher by 55 to 60 m than at present.
 By dating relict corals, Gupta (1972) and Gupta and Amin (1974) concluded that the sea levels on
the Saurashtra coast stood higher by 2 to 6 m around 120,000 years BP.
 Data on the changes in sea level between 120,000 years and 11,000 years BP are not available, a
period when sea level was substantially lower than at present.
 The sediment distribution map of the Arabian Sea (Geological Survey of India, 1975) shows a
linear band at water depths of 75 to 100 m. This sand body could represent an ancient beach and
shallow marine environment, which would indicate a lowering of sea level all along the west coast.

18.  Nair (1975) recognized several well-defined terraces off Ratnagiri at -65, -75, -85, -95 m.
Radiocarbon dating of the samples from these terraces has shown their ages ranging from 9000
to 11,000 years BP.
 This finding agrees well with the global picture in which sea level was at its lowest ( -100 to -150
m) between 15,000 and 18,000 years BP following the last glacial maximum.
 Therefore, the terraces and the sand body must have formed when the sea was transgressing.
During this transgressive phase, sea level rose rapidly at about 1 cm per year until 6000 years ago
(Hashimi and Nair, 1988).
 There is some evidence to show that 6,000 years ago, the sea level was a little higher than it is
today. For instance, the evidence reported by Verma and Mathur, the oyster beds on the Goa
coast, and the relict corals revealed along the Saurashtra coast (Gupta, 1972; Gupta and Amin,
1974; Somayajulu et al., 1985) are all examples (1979). These deposits suggest that around 6000
years ago, the sea level was around 2 m above present.
 The sea appears to have switched from a transgressive to a regressive phase 6000 to 3500 years
BP. A marine archaeological survey conducted off the Saurashtra coast by Rao (1987) revealed
the existence of a submerged port city of Dwaraka.

19. figure: Summary of the coastal cliff profiles studied and described from southern Saurashtra.

20. CONCLUSION
 Eustatic changes refer to global variations in sea level.
 The quaternary period is characterized by a series of glacial and interglacial cycles that
have had a profound impact on eustatic sea level changes.
 Around 125 m of eustatic sea level rise have occurred during the past 20,000 years as
a result of glacier melting. The majority of it occurred between 15,000 and 7,500 years
ago during the significant ice sheet melting in North America and Eurasia.
 There was a huge Eustatic change occur during quaternary period in India,basically in
west coast of india.

21. REFERENCE
 Valdiya, K.S, The Making of India Geodynamic Evolution, Second Edition
 Wadia, D.N, geology of india
 Tectonic, eustatic and isostatic changes along the indian coast | springerlink
 Https://www.Researchgate.Net/publication/290987159_quaternary_sea_level_changes_al
ong_indian_coast
 https://www.nap.edu/read/1345/chapter/9
 https://www.cambridge.org/core/books/abs/quaternary-sealevel-changes/causes-of-
quaternary-sealevel-changes/8D949BOAF418A6BC7206965CE64498DE