A preliminary age calibration for the post-glacial-maximum period


Figure 1. Long-age uniformitarian sea-level curve for the post-glacial-maximum period (after Rohde 2 )

In the past 20 years a number of studies have been published on the rise in global sea level since the last glacial maximum. The dates of the last glacial maximum and the change of sea level with time were based on long-age dating assumptions using a variety of methods, and fitted into the uniformitarian timeline.1 Given that the glacial maximum occurred toward the end of the post-Flood Ice Age, these curves allow us to develop an age calibration to convert secular, long-age dates into dates within biblical history.

Figure 1 shows the current secular view on sea-level rise since the end of the last glacial maximum. This graph was prepared by Robert Rohde from several published papers2 that included data assembled from numerous other sources. The actual sea levels had been adjusted for vertical geologic motions such as continental rebound, connected with the removal of continental ice, and hydrostatic rebound, due to the increased weight of water in coastal areas. However, it is the dates on the chart rather than the sea levels that are primarily needed for an age calibration.

Developing the calibration curve

Figure 2. Fitted calibration factors to convert uniformitarian ‘age’ to biblical age for the post-glacial-maximum period. Biblical age is obtained by multiplying the secular age by the relevant calibration factor. Diamonds are calibration points from table 1.

An analysis of the magnitude of the sea-level fall needs to be evaluated, but this is outside the scope of this article. The graph shows the last glacial maximum occurring at 22,000 years ago, when sea level was at its lowest, and the sea-level rise reaching the present level at about 7,000 years ago, all within the secular timescale.

It was the biblical Flood that provided the conditions on Earth that caused the Ice Age immediately after the Flood. The primary driver was warm oceans and a secondary factor would have been volcanic dust and aerosols high in the atmosphere.3 In his monograph on this topic Oard discusses the timing of the Ice Age, namely the time to reach glacial maximum, and the time for the ice sheets to melt back to their present size.

His ‘best estimate’ for their buildup to glacial maximum, based on a 25% depletion of solar radiation and a 12.5% decrease in the current values of the atmospheric and oceanic heat transports, is 500 years.3 From energy balance considerations he found only a short time was required for the oceans to cool, and the ice sheet to melt back. The periphery of each sheet would melt first, and quickly, and the interiors more slowly. He concluded that the best estimate for the melt-back time to present size was 200 years.3

Table 1. Calibration points and factors for post-glacial-maximum period.

The timing of the Ice Age is tied to the timing of the Flood, which, in round figures, can be taken as about 4,500 years ago.4 The Ice Age maximum would thus have been about 4,000 years ago and the oceans would have reached their current level about 3,800 years ago.

Hence we equate the secular date for the last glacial maximum (22 ka ago) to the biblical date of 4,000 years ago. And we tie the secular date when the oceans reached their present level (7 ka ago) to the biblical age of 3,800 years ago. The 200-year period of ice melt-back results in a very tight compression of the major part of the secular timescale. This gives us three points for our calibration curve (table 1).

Figure 3. Calibration curve to convert secular, long-age ‘dates’to biblical dates for the postglacial-maximum period. Biblical age is obtained from the secular age by reading from the graph

We would expect the secular dates to better match historical dates (and thus biblical dates) for recent history over the last 2-3 ka, and for the calibration factor to be close to 1.0 in this range. Further, we would expect the separation between the two scales to increase with increasing age due to the effects of the Flood and the Ice Age, and thus the calibration factor would diverge more greatly from 1.0. As the secular time increased into multiple tens of thousands of years we would expect the calibration factor to become smaller and smaller, tapering off into an exponential decay type of shape. Based on this we can fit by eye a reasonable calibration curve for the period, as shown in figure 2.

From the calibration factors of figure 2 we can calculate a calibration curve as shown in figure 3, which allows us to read the biblical age for the post-glacial-maximum period when we have the uniformitarian age.


This is a broad-brush approach to adjusting secular dates to fit in with ages based on the historical reports in the Bible. It may be claimed that the method is circular, that we have massaged the figures to get the answer that we want. This is correct, but this is the way that all dating methods work.5 All methods begins with researchers making careful measurements on samples in the present. Then they must make assumptions about the past to calculate an ‘age’. But no one stops there. All researchers compare results with other age information, and adjust assumptions and interpretations until the calculated age makes sense within its context. So, this exercise of converting secular ages to match biblical history simply follows the normal practice of geochronology, but with the great advantage that biblical history is reliable.

The carbon-14 (C14) method is the one most widely used for the period of time back to about 40,000 years ago, and so this calibration curve would reflect the sorts of adjustments that would need to be made to C14 ‘dates’ in order to obtain actual dates. The need for significant correction to C14 dates beyond a few thousand years has been long recognized even by secular geochronologists, as Pilcher discusses:

“It is most likely that at the end of the last glaciation there were considerable perturbations of the global carbon cycle with the release of old carbon from ice, and an increase in biomass as temperatures rose. … It is hard to believe that these changes would not have had dramatic effects on the radiocarbon levels in the atmosphere.”6

Secular geochronologists already have calibration curves for the C14 method to make the results agree with other methods and other information, such as dendrochronology. However, we would anticipate even larger corrections would be needed for C14 dating than those used by secular geochronologists because they ignore the dramatic effects of the Flood.

The Flood would impact many factors, including non-equilibrium levels for C14 in the atmosphere immediately after the Flood, the burial of low C14 preFlood vegetation, increased volcanism after the Flood producing ‘old carbon’ in the atmosphere, revegetation of the earth after the Flood, and changes to the earth’s magnetic field affecting C14 production in the upper atmosphere. A useful discussion of the factors affecting C14 dates as they would have been impacted by the biblical Flood and the post-Flood recovery is presented by Batten.7


The calibration curve (figure 3) would have general application to all dates published within the secular long-age scheme because all dating methods are compared with, and calibrated against, each other in order to obtain a consistent suite of dates. While figure 3 can be considered a general calibration curve, we would anticipate that there would be temporal and regional anomalies depending on the dating method and the study location. We will need to consult more reliable sources and obtain other information in order to refine and test the curve.

Figure 4. Sea level curve of figure 1 adjusted to the biblical timescale using the calibration factors of figure 2.

Update 16 May 2017

Following several requests by those who commented on this article, we publish here the sea level curve related to the biblical timescale (the calibration curve of figure 2 applied to data of figure 1). The sea level changes are based on the timing of the Ice Age published by Oard (ref. 3). Notice that in this figure 4, sea level rises rapidly after 4000 years ago (Ice Age Maximum) and remains very stable since. The Flood is taken at 4,500 years ago, so there would have been a similarly rapid sea-level drop after the Flood to the glacial maximum. Oard has argued that the ice sheets during the ice age were much thinner than the thickness assumed by long-age geologists. Consequently, he concludes that the sea level drop was only some 55 m rather than the 130 m shown in the diagram.

References and notes

  1. Yokoyama, Y., Lambeck, K., De Decker, P., Johnston, P and Fifield, L.K., Timing of the Last Glacial Maximum from observed sea-level minima, Nature 406(6797):713–716, August 2000 | doi:10.1038/35021035. Return to text.
  2. Rohde, R., Post-glacial sea level, Global Warming Art, globalwarmingart.com, accessed July 2014. Rohde collated information from:
    (1) Fleming, K., Johnston, P., Zwartz, D., Yokoyama, Y., Lambeck, K. and Chappell, J., Refining the eustatic sea-level curve since the Last Glacial Maximum using far-and intermediate-field sites, Earth and Planetary Science Letters 163(1–4):327-342, 1998.;
    (2) Fleming, K.M., Glacial Rebound and Sea-level Change Constraints on the Greenland Ice Sheet, Australian National University, PhD Thesis, 2000.
    (3) Milne, G.A., Long, A.J. and Bassett, S.E., Modelling Holocene relative sea-level observations from the Caribbean and South America, Quaternary Science Reviews 24 (10–11):1183-1202, 2005. Return to text.
  3. Oard, M.J., An Ice Age Caused by the Genesis Flood, Institute for Creation Research, El Cajon, CA, 1990. Return to text.
  4. Hardy, C. and Carter, R., The biblical minimum and maximum age of the earth, J. Creation 28(2):89–96, 2014, conclude that the Flood probably occurred between 2600 BC and 2300 BC. Return to text.
  5. Walker, T., How dating methods work, Creation 30(3):28–29, 2008; creation.com/dating-flaws. Return to text.
  6. Pilcher, J.R., Radiocarbon dating; in: Smart, P.L. and Frances, P.D. (Eds.), Quaternary Dating Methods—A User’s Guide, Quaternary Research Association, Technical Guide No. 4, Cambridge, pp. 16–32, 1991. Return to text.
  7. Batten, D. (Ed.), The Creation Answers Book, (4th edn.) Creation Book Publishers, pp. 68–73, 2012. Return to text.

Helpful Resources

What about the Ice Age?
by Dr Don Batten
US $0.60
Life in the Great Ice Age
by Michael J Oard, Beverly Oard
US $16.00
The Creation Answers Book
by Various
US $15.00
Rock Solid Answers
by Michael J Oard, John K Reed
US $20.00
Missoula Flood Controversy
by Michael J Oard
US $19.00

Readers’ comments

Matthew B.
Christian R. raises a good point: what connection did the Ice Age have with Abraham and Ur? By Ussher, the Flood ended in 2348 BC and Abraham was born in 1996 BC. If the Ice Age lasted about 700 years, he lived in it.
If Ur was in S. Iraq problems arise with this creationist Ice Age model (which I think is accurate). Christian referred to the ARJ; in that journal in v. 4 is “Where in the World is the Tower of Babel,” (search it online). Anne Habermehl reasons that Babel must be in N. Mesopotamia. She talks of a ridge north of Ur and Babylon that cuts across the valley between the Euphrates and the Tigris. This escarpment, 6-15 m high, is about 76 m (249 ft) above sea level and is thought to be an ancient ocean shoreline- the post-flood shoreline. The ocean (Persian Gulf) level dropped during the Ice Age, exposing a valley that the rivers would go down. Habermehl says “what was in south Iraq before this post-Ice Age meltdown was a deeply folded trough…. The alluvium in the south of Iraq that we see today would not yet have been there at the time of building the Tower. This alluvium is a delta that was formed later on, well after the Babel dispersion, by vast amounts of materials washed down... during the catastrophic period of the Ice Age meltdown.” Babylon sits on 30 m of this Ice Age strata, and the deposit under the popular Ur is even deeper (up to 270 m).
Logically, Abraham (1996 BC) could not have lived in Ur during the Ice Age if Ur was built after it brought the land it was on (c.1700 BC). Therefore Ur must be in northern Mesopotamia (not long covered in water and silt). In fact, there is historical, linguistic, and geographical evidence to place Ur in SE Turkey. Until Sir Leonard Wooley came along in 1922, tradition placed Ur at modern Sanliurfa (Urfa), Turkey.
Robert O.
I am 67 years old. I grew up on St Petersburg Beach, Florida only one (1) block from the Gulf of Mexico. As a young boy I would go swimming, fishing, and crabbing everyday. I remember when they built the seawalls at the end of our street. As a young fisherman I noticed the high and low tide events. Recently I returned to that same seawall (50+ years later). I was there for both the high and low tides. I have a pretty good memory, yet I could not see any differences in sea levels of the tide events of 50 years ago with today. If you think the sea levels are going to change significantly in the next 50 years ... your being deceived.
Dave F.

Just posted your info on two creation / evolution Facebook pages.
Matthew B.
I would like to see a diagram where the calibration is applied to figure 1. Or maybe a chart with the sea levels during the ice age can be found elsewhere on your site?
The methods used in this article are similar to those of Watt and Hansen, in Secrets of Polar Ice. While their main task was to use delta oxygen 18 to determine the relative climate of the ice age, they also included data on the Nile and Lake Chad levels. A spike in their water levels followed by a sharp drop around 1700 BC suggests Joseph's famine.
From your calibration curve, am I correct in estimating that water levels may have been 2-8 meters lower than present around 3500 BP? That would indicate that the Red Sea geography would have been similar to that of today in 1500 BC, around the time of the Exodus. Thus, even though the sea levels were still rising, the crossing site does not need to placed as if the water was much lower then.
Pharaoh's army could have drowned in either gulf of the Red Sea because they were nearly as deep as today. On the other hand, the rising sea levels damage the Bitter Lake crossing theory, because they would have been further above sea level, thus likely shallower than required. The hypothesized channel between the lake and the gulf would have been above the erstwhile sea level, causing the water to drain from the shallow lakes into the Red Sea, making it doubtful that Pharaoh's army could have perished in the Bitter Lakes.
Thanks for the introduction to the subject! I hope to see more on it.
Tas Walker
I'll publish the figure you ask for as an update to the article.
Joseph B.
It would be interesting to see figure 1 plotted again using the Biblical dates.
Tas Walker
Hi Joseph, There have been a few requests for this so I will upload a figure. The sea level changes rapidly after glacial maximum based on the Oard's timing (ref. 3). The Flood is taken at 4,500 years ago, so there would have been a similarly rapid sea-level drop after the Flood to the glacial maximum.
Edward P.
So, it would seem that "global warming" is nothing more than an inadvertent correction to the geologic timescale putting it in line with the Flood's timescale. If one were to use long ages, it would make sense that it would look like a corresponding acceleration in the global temperature over the last 100 years or so when real time measurements have been used.
Jim B.
So, if the Maximum of the Ice Age is ~4000 BC, that is about 2000 after Creation, or 344 years after the Flood. Can we assume that the IceAgeMax might have been the lowest ocean levels? During these 3+ centuries animals would have been dispersing, and after a 2 century period of defiance humans finally scattered after Babel. So, the period of relatively lower sea levels there would have been kingdom building and the establishment of coastal cities in many locations around the globe from the time of the Flood (~2344BC) until the IceAgeMax (~2000BC). But then in the next ~150 years (till ~1800BC) due to melt, run-off, mountain-building (Ps. 104:7-8), there may have been a bit of a scare in many mini-floods (Like the Jishi Gorge Flood of Yao, Black Sea Flood), that resulted in inundations of Coastal cities and various water-gaps between continental land masses (Gibraltar, English Channel, Bosporus, Bering Sea, Australia).

These Ice Age time-frames seem to me to have a significant contribution to our understanding of post-flood animal dispersion, and human migration and the advance of human populations and civilizations globally. Interesting Article. Thanks.
Christian R.
In 2013, Dr. Andrew Snelling and Mike Matthews published an article in Answers Magazine in which they gave a date of roughly 2000 BC for the end of the Ice Age, primarily because it was only until after the glaciers started to melt that the cities like the one of of Abraham's birth, Ur, we're founded (correct me if Im wrong but I think Abraham lived around 1800 BC). Obviously, Ur existed before Abraham's birth. So if Abraham lived 3800 years ago, and glacial maximum was 4000 year ago, was there enough time for the Persian Gulf to fill with water and for Ur to be founded all before Abraham's birth?
Tas Walker
This is a preliminary calibration which assumes the Ice Age Maxumum was 2000 BC. Babel was well before Abraham and that was a significant city. The other cities would have been build after the dispersion from the Tower of Babel and that was before Abraham. Your date for Abraham is too late. Search for "Ussher Timeline" on this site to get a useful chart of the chronology.
Gert P.
I do not follow the whole global warming debate, but I still recall all the claims about rising oceans and the claims that we as humankind are facing end of life as we know it. Yet the post glacial sea level chart paints a very different story, sea levels have reached a plateau and seems to be very stable for the past 8000 long-age uniformitarian years. Maybe it is simply my lack of knowledge on this subject, but it seems like a lot of "monster in the cupboard" stories when it comes to global warming and sea level changes.

On a different note, I was hoping to see you applying the calibration to figure 1 and have it redrawn to the biblical time scale.
John A.
Fascinating. I find it intriguing that Fig 3 looks almost like a first-order step change response. Almost. I wonder why that might be?
Tas Walker
Looks like you have found an interesting project to explore!

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