Archaeomagnetic Dating

On December 18, 2023, a technical paper was published in the prestigious Proceedings of the National Academy of Sciences of the USA, which received a lot of publicity in the popular science press. The paper was titled “Exploring Geomagnetic Variations in Ancient Mesopotamia: Archaeomagnetic Study of Inscribed Bricks from the 3rd–1st Millennia BCE.”1 So why all the fanfare?

The 2023 Published Study

The paper reported the results of a study by an international team of researchers on 40 inscribed bricks that are conventionally dated as from the third through first millennia BC (or, as they report, BCE, before the common era) to identify the strength of the earth’s magnetic field when the bricks were made. By analyzing this archaeomagnetism (“fossil” magnetism), archaeologists believe they can identify changes in the earth’s magnetic field strength over time and then compare those results with the levels recorded in excavated objects, such as pottery. They claim this can establish a relative chronology for the objects. However, to create an absolute chronology, archaeologists must check their results against objects that they believe are already accurately dated. Pottery fragments or standard mudbricks cannot be dated precisely, so this is where the inscribed clay bricks came into their objectives. This is one of the first large-scale studies ever conducted for Mesopotamia.

Throughout Mesopotamia, bricks were stamped with royal inscriptions that mention the kings associated with specific building projects. Among the inscribed bricks used in this study were nine bricks likely looted from quay walls constructed by Adad-Nirari I at Ashur and bricks inscribed with the names of well-known Mesopotamian kings, including Nebuchadnezzar II, Shulgi, and Tukulti-Ninurta I. Utilizing established king lists, scholars believe they already have accurate dating for most Mesopotamian kings’ reign, with only a few short periods of uncertainty. This paper’s research team, then, was able to take the “fossil” magnetic results provided by the chosen bricks to “create a precise baseline of the magnetic field at specific points in time.”2 Minor variations in the magnetic field occur regularly, so the archaeomagnetism dating method would appear to allow excavated objects to be dated to within a few decades.

Writing of the significance of their study, the authors suggested that reconstructing the behavior of earth’s magnetic field during archaeological periods is crucial for both achieving a better understanding of the field and related natural phenomena and for providing a basis for absolute dating of archaeological materials. Having analyzed the inscribed baked bricks from Mesopotamia from the third–first millennia BC, which they claimed are well-dated based on their association with well-known regional kings, they concluded that they had provided accurately dated and highly precise archaeomagnetic intensity data for the region. Furthermore, they claimed their results demonstrated the potential of this archaeomagnetic analysis of baked bricks and facilitated a better understanding of the field, including insights regarding the length of the Babylonian “dark ages,” that is, from the end of the Old Babylonian period to the Kassite period (c. 2004–1155 BC) in the standard chronology and the so-called Levantine Iron Age geomagnetic anomaly (1050–550 BC). Thus, their results provided a basis for archaeomagnetic dating in a key region (that is, Mesopotamia) in the history of complex societies. Additionally, they stated that based on a comparison between their results and the well-established archaeomagnetic curve for the Levant, they were carefully suggesting that the magnetic data support the low (that is, shorter) chronology for Mesopotamia.

What Is Archaeomagnetic Dating?

Archaeomagnetic dating utilizes the change in earth’s magnetic field to potentially date objects.

Archaeomagnetic dating utilizes the change in earth’s magnetic field to potentially date objects. Ancient artifacts, such as ceramics, pottery, or mudbricks, may include tiny particles of iron oxide (often the mineral magnetite, Fe₃O₄) which, when heated to high temperatures (>1400°F or 765°C), act like a compass needle, aligning internally to the direction and intensity of the magnetic field when the clays were baked with heat. Similarly, when such objects were set on fire during the destruction of a city, the magnetic conditions at the time were then locked in as their magnetic particles subsequently cooled below what is known as the Curie temperature, which for magnetic iron oxide is ~1085°F (585°C). This is known as thermal remanent magnetization.

The earth’s magnetic field has two main components. The stronger component, polarity, which indicates whether the magnetic north pole is aligned more closely with the geographical north pole or with the geographical south pole, has alternated at irregular intervals in the past (primarily during the Genesis flood). The weaker component is known as the magnetic secular variation. This component varies regionally and the changes tend to be gradual. A compass needle does not actually point to the true North Pole but to a direction that is a function of the North Magnetic Pole. And the local secular variation yields a magnetic declination, which is the angle between magnetic north and true north at a particular location on the earth’s surface. As already discussed, the magnetic declination at any given time can be “frozen” into clay that contains magnetite and has been heated above the Curie temperature. Thus “fired” ancient artifacts such as pottery and bricks can yield the magnetic declination from the last time they were fired or used.3

By reconstructing the pattern of these changes of the earth’s magnetic field over the last few millennia, archaeologists claim they can use these data “to pinpoint, with relative certainty, the date of these [ancient artifacts].”4 It is claimed that archaeomagnetism appears to provide a far more accurate method of dating than supposedly more common “absolute” methods, such as radiocarbon dating, which often has an uncertainty of a century or more, and the standard ceramic typology method. Indeed, archaeomagnetism appears to be “particularly useful when it comes to remains from 800–400 BC, a period for which radiocarbon dating does not enable high resolution dating”5 (see below).

Archaeomagnetic dating requires undisturbed objects, like bricks, that have a high likelihood of containing remanent magnetism from the last time they had cooled through the Curie temperature. There must be sufficient masses sampled from the objects to include adequate magnetite to preserve the remanent magnetism. In addition, the objects need to have been in an area for which a secular variation curve (SVC) of measured “fossil” magnetic declinations exists. Once the paleodirections of enough such archaeological objects (that have also been independently dated) are determined, they can be used to compile a secular variation record for a particular region. This is exactly what this recently published study on inscribed bricks was endeavoring to do for Mesopotamia.

Keep in mind that ancient, inscribed objects like the bricks used in this Mesopotamia study are usually part of museum exhibitions or valuable collections. Although damage is minimal, sampling for magnetic analysis is destructive, so permission had to be obtained for this inscribed brick study from the Iraqi government. Normally, a number of samples are removed from each archaeological object by encasing them in nonmagnetic plaster within nonmagnetic molds, marked for true north at the time of collection, and then sent to an archaeomagnetic laboratory. In the Mesopotamia brick study, samples were sent to the Scripps Institution of Oceanography Paleomagnetic Laboratory, University of California San Diego, La Jolla, CA. Each of the samples was measured in a specialized, very sensitive magnetometer known as a SQUID (superconducting quantum interference device), capable of measuring extremely weak magnetic fields, to determine the thermal remanent magnetism of each sample. The results were statistically processed to generate vectors showing the three-dimensional magnetic declination, which yields the location of the north pole at the time of the last thermal event (“fossil” magnetism) recorded in each sampled object. Data from each object are usually compared to the regional SVC to determine the best-fit date range for the object’s last firing.

Previous Successful Studies

It is helpful to know that there have been previous very successful archaeomagnetic dating studies that provided anchor points in the SVC for Israel. Two such studies involved the accurate archaeomagnetic dating of archaeological materials burnt during the destruction of cities by conquering armies.

The first study was of the destruction of Jerusalem by the Babylonians in August of 586 BC.6 The researchers analyzed 54 well-preserved floor segments from a monumental structure that had served as an elite or public building that had collapsed while it burned. From the reconstructed paleomagnetic directions, the authors concluded that the segments had originally been part of the second-story floor. They firmly connected the time of the magnetic acquisition recorded in the floor segments to the date of the destruction. Furthermore, the authors’ objective was to demonstrate how archaeomagnetic data derived from a historically dated destruction can thus serve as an anchor point for archaeomagnetic dating.

The second study also used the approach that applied archaeomagnetic investigation to the remains of ancient towns that were destroyed by fire.7 Many biblical sites have destruction layers associated with famous conquerors’ military campaigns. Such catastrophic events created these layers, which are now invaluable to archaeologists when dating these sites. An international team used archaeomagnetism to analyze 21 destruction layers at 17 different sites to establish the dates of their destructions. They reportedly were able to “pin down the dates for several biblical wars and campaigns, including those of Shishak (1 Kings 14:25), Hazael (2 Kings 12:1), Jehoash (2 Kings 14:11), Tiglath-Pileser Ill (2 Kings 15:29), Sennacherib (2 Kings 18–19), and Nebuchadnezzar (2 Kings 25).”8

Although most of the destruction layers they studied corresponded to conflicts recorded in the Bible and other sources, determining precisely when they occurred or which layers correspond to which campaign is tricky, particularly for several conflicts during the period c. 1000–586 BC that occurred over a relatively short period of time. This had led to some disagreement, such as with the Israelite city Beth Shean, whose destruction layer has been attributed to either Shishak or Hazael. Through the application of this new archaeomagnetic dating framework, the authors found that it can be confidently attributed to Shishak around 920 BC, nearly 100 years before the campaign of Hazael.

Similarly, the archaeomagnetic dating framework they constructed dated the destruction of the Judahite city of Beth Shemesh to early in the eighth century BC, which agrees with the biblical account of its destruction by the Israelite king Jehoash (2 Kings 14:11–13). Several other destruction layers were linked to biblical battles, including at Tel Zayit and Tell Beit Mirsim. This archaeomagnetic dating framework also allowed the archaeologists to distinguish between the Babylonian campaigns of 600 and 586 BC, showing that the Philistine city of Ekron was destroyed in the earlier rather than the later campaign.

Highlighting the Problems: Objective Calibration

The archaeomagnetic data from both these previous studies provide chronological insights that help link archaeological finds with military campaigns, corroborating the history of the biblical kingdoms of Israel and Judah contained in Scripture. These interdisciplinary studies have also reconstructed the behavior of the earth’s magnetic field during a unique period—when it was changing rapidly and more than double the intensity of today. But can the recently published study of the inscribed bricks from Mesopotamia be accorded the same degree of certainty for extending the archaeomagnetic timescale back into the third millennium BC?

To create an absolute chronology, archaeologists need to test their results against objects that are already securely and precisely dated.

The answer is no! What is not adequately emphasized in all these studies is that for archaeomagnetic dating to work objective calibration of these “fossil” magnetic data with anchor points to known historical dates is essential. In other words, to create an absolute chronology, archaeologists need to test their results against objects that are already securely and precisely dated. Doing so was very easy in the cases of the two previous studies that analyzed destruction layers for their archaeomagnetic signatures, especially in the first study which focused on the destruction of Jerusalem by the Babylonians in August of 586 BC.

As the authors of that study commented, it is important to note that all historical and archaeological data show that there was no major destruction event in Jerusalem for centuries before or after the Babylonian destruction in 586 BC. The archaeological data they reported and the strong evidence of the destruction of that monumental structure by fire correspond exactly with the biblical description of the conquest and the systematic destruction of Jerusalem by fire in August 586 BC. According to the Bible’s description, this destruction was executed by professional “city destroyers,” under the command of Nebuzaradan, a highly ranked Babylonian official:

In the fifth month, on the seventh day of the month–that was the nineteenth year of King Nebuchadnezzar, king of Babylon–Nebuzaradan, the captain of the bodyguard, a servant of the king of Babylon, came to Jerusalem. And he burned the house of the Lord and the king’s house and all the houses of Jerusalem; every great house he burned down. (2 Kings 25:8–9)

This detailed biblical description of the destruction of Jerusalem by the Babylonians in 586 BC is considered historically reliable by the vast majority of researchers, who really only affirm what God’s inspired Word records. It’s hardly surprising to us that the above description and other biblical references to this event enable dating of the destruction almost to the day. Besides emphasizing the burning of the temple and the king’s palace, the biblical record emphasizes the destruction of elite houses.

Furthermore, that study’s authors discuss the significance of this destruction of Jerusalem event extending beyond its historical context. From the perspective of the behavior of the earth’s magnetic field, 586 BC was believed to follow a period of an intense high-field “anomaly” identified in the Near East and in Western Europe. From the viewpoint of establishing an objective standard chronology for ancient history, the destruction of Jerusalem in 586 BC took place during a 400-year-long flat portion in the conventional radiocarbon calibration curve (the so-called Hallstatt Plateau, during which atmospheric radiocarbon was nearly constant). This leads to a huge uncertainty in the radiocarbon dates within this interval. Thus, in their study, the authors had to show how the radiocarbon calibration curve of a synthetic radiocarbon age of 2485±25 BP (Before Present) for the Babylonian destruction of Jerusalem corresponds (by reverse calibration) to ca. 586 calibrated BC (cal. BC). The 95.4% confidence interval of the calibrated age spans more than 250 years (771–517 cal. BC), and the 68.2% confidence intervals range over 216 years (756–545 cal. BC).

This admission that radiocarbon does not accurately date this well-attested Babylonian destruction of Jerusalem without subjective manipulation means that radiocarbon dating cannot be the objective absolute method it is so often claimed to be. Worse still, recent Egyptological scholarship has proven that dates known from historical-archaeological evidence to be earlier than 1400 BC appear older when associated organic material is radiocarbon dated and that this offset increases steadily when going back further in time. For example, radiocarbon dates for material from around 1500 BC are 100–120 years older, while material from the so-called Early Bronze Age (which ended around 2000 BC) is about 150–300 years older than conventional archaeological assessments.9

However, a truly shocking discovery made over the past 40 years is that organic materials that are conventionally dated at up to 500 million years old, such as coal, oil, and fossils, all still contain measurable ¹⁴C and yield radiocarbon ages on the order of 50,000 years.10^,11 Indeed, samples from US coal beds conventionally dated from 40 to over 300 million years old all yielded similar measurable ¹⁴C levels, with an average radiocarbon age of ~49,600 years. These radiocarbon results thus strongly imply that the plant life which formed the coal and the animals which were fossilized were all alive only thousands of years ago. From a biblical standpoint these organisms correspond to plants and animals that perished in the flood cataclysm of Noah’s day, only ~4,500 years ago. That implies something happened at the time of the flood to cause grossly inflated early post-flood radiocarbon ages.

Now it needs to be remembered that all radiocarbon ages are based on assuming that the past rate of ¹⁴C production in the upper atmosphere has always been the same as the current measured rate. Thus, the grossly inflated early post-flood radiocarbon ages calculated from the measurable ¹⁴C levels in archaeological materials could be due to the ¹⁴C production rate in the upper atmosphere being lower in that period relative to today’s measured production rate. And the most likely cause for that would be the earth’s magnetic field being stronger in the past, which has even been confirmed by these archaeomagnetic studies of destruction layers of conquered cities in Israel that revealed the magnetic field was twice as intense as today’s measured magnetic field intensity even back in the 1000–500 BC period.

This finding that around 1000–500 BC the earth’s magnetic field was twice the intensity as today’s measured field is fully consistent with the evidence from measurements over the last 200 years that the earth’s magnetic field moment (its energy and strength) is decaying exponentially.12 This limits the age of the earth to <10,000 years, rather than the >4.5 billion years claimed by secular geologists, based on their assumption that the earth’s magnetic field is generated by a dynamo in the earth’s core. However, all the evidence points to the earth’s magnetic field instead being generated by decaying electrical currents in the earth’s core. Furthermore, the decline in the magnetic field strength and energy was increased during the flood due to mantle flow above the fluid outer core that caused magnetic reversals. The instabilities this caused explains the field fluctuations the archaeologists are finding in these bricks and other archaeological artifacts.

Alternately, another likely cause of the grossly inflated flood and post-flood radiocarbon ages is change in the decay rate of ¹⁴C atoms during the global flood and then after the flood as the earth was recovering and stabilizing. Several lines of evidence have demonstrated that radioisotope decay rates were grossly accelerated by six orders of magnitude during the flood catastrophe,13 but then rapidly decelerated at the end of the flood into the early post-flood period. There was also a systematic pattern in the evidence indicating that the acceleration of the decay rates varied according to the atomic weights of the parent radioisotopes: the heavier parent radioisotope, the greater the acceleration of the decay rate. Thus, since the half-life of ¹⁴C at 5730 years is very fleeting, its decay rate during the flood would have only been minimally accelerated. But there would still be the re-stabilizing period in the early years after the flood.

Thus, if one seeks to utilize these radiocarbon results to calibrate the radiocarbon curve between the flood and, say, 1400 BC, one is faced with a daunting challenge. The challenge is that over that relatively brief interval of time, the radiocarbon level in fossils increased by a factor of about 200! Until recently no one had offered a conceivable way to add radiocarbon to the atmosphere and biosphere at a sufficiently high rate to increase the radiocarbon level so quickly and dramatically. However, recently it has been pointed out that if a temporary reduction of the strong nuclear force that serves to hold together atomic nuclei were the cause of the accelerated nuclear decay documented to have occurred during the flood,14 then that temporary reduction in the strong nuclear force probably would have increased the rate of nuclear fusion in the core of the sun.15 The extra heat thus produced would have temporarily increased the sun’s production of high energy particles and led to a significant increase in radiocarbon production in the earth’s atmosphere during the ice age after the flood.

Is there evidence that the radiocarbon level during the ice age increased rapidly? Perhaps. In 2001, radiocarbon measurements were reported from a marine clam Spisula subtruncata in an ice age core from northwestern Germany.16 Measurements were made both on the inside and outside of the shell. The average radiocarbon value for the outside of the shell was 0.3 percent modern carbon (48,000 yr), whereas for the inside it was 0.67 percent modern carbon (41,500 yr). At face value, this potentially indicates the radiocarbon level more than doubled in the lifetime of this clam. Further similar analyses are needed to confirm this possibility.

Nevertheless, the assumption that archaeomagnetism can be calibrated against radiocarbon much beyond 1500 BC is mistaken.

Nevertheless, the assumption that archaeomagnetism can be calibrated against radiocarbon much beyond 1500 BC is mistaken. The errors currently associated with radiocarbon, especially beyond 2000 BC, become extreme.

A further assumption in archaeomagnetic dating of the Mesopotamia inscribed bricks is the accuracy of the archaeological chronology secularists have constructed, which diverges markedly in its earliest stages from the biblical chronology. There is solid evidence that those Mesopotamian king lists were inflated with years of reigns to make some kings look more important.17 Furthermore, the archaeological evidence for those kings has been assigned dates based on radiocarbon and other dating methods such as pottery styles. And in the Egyptian chronology, it is maintained by many biblical scholars that it is likely parallel reigns in various parts of Egypt at different times are not considered by secular archaeologists, so instead, all the pharaohs are listed as though they reigned sequentially, thus inflating the Egyptian archaeological chronology.18

Therefore, there are no objective, independent physical parameters or secular historical certainties against which the archaeomagnetic data can be calibrated. This guarantees that archaeomagnetic dating is not the reliable yardstick as it is claimed to be in the Mesopotamia inscribed brick study. Furthermore, these various assumptions, as discussed above, are interwoven so that to use the various methods built on them involves inherent circular reasoning. This also makes the claims of archaeometric dating being so accurate very dubious.

God’s Word Is the Authority

So is there an authoritative document that gives us a reliable account of human history against which we can calibrate all dating methods, including the radiocarbon, archaeological, and archaeomagnetic methods? Yes, it is God’s Word, the God-inspired Bible (2 Timothy 3:16; 2 Peter 1:20–21), His eye-witness account of human history beginning in Genesis. And God never lies (Titus 1:2), so His Word can be trusted.

Beginning in Genesis 5 and 11, God provides for us a detailed chronology from the creation of the first man Adam through the subsequent generations to Abraham after the flood and Babel. This chronology is based on direct father-son relationships, the years calculated from the birth of a patriarch’s eldest son to the subsequent birth of that eldest son’s eldest son. Then from Genesis 12 onward through the Old Testament, we are provided with copious chronological details that allow the biblical chronology of human history to be fleshed out meticulously.

The only absolute standard for calibrating archaeomagnetic, radiocarbon, and archaeological dating methods is the biblical chronology, because it comes to us with the authority of God’s Word.

Indeed, both the two previously published archaeomagnetic dating studies described above were based on archaeological materials from destruction layers of cities in Israel where the dates of the destruction were already known from the biblical text! In other words, even these secular published studies acknowledged the absolute reliability of the Bible. Yet the recently published study of the archaeomagnetic dating of Mesopotamia inscribed bricks ignores the biblical chronology. If the researchers had similarly calibrated their archaeomagnetic dating results against the biblical chronology instead of against the faulty secular chronology based on king lists with inflated reigns, then their derived archaeomagnetic dates would have been much lower.

In conclusion, the only absolute standard for calibrating archaeomagnetic, radiocarbon, and archaeological dating methods is the biblical chronology, because it comes to us with the authority of God’s Word.