Glacial Origin of Jars at Plain of Jars, Laos - PDJ Jars Origin Theory - HoboMaps.com - Go to Plain of Jars Info Page - - Home

Since the discovery of stone "quarries" that were used as source material for the carving of the magalithic jars found at the Plain of Jars (PDJ), many people assume that all of the jars in the the area have been carved from quarried stone and that some form of transport was required to get these jars from the quarry to where we see them today. The Author believes this may be true for the majority of jars found at the PDJ but that some jars may have been carved from naturally-situated boulders where early people found them lying about on the surface and that no transport was involved. These naturally-situated boulders may have come to their positions by a variety of natural geologic events including the possibility of being carried to where they are by glacial activity in the distant past. Jars carved from these naturally-situated boulders would likely be scattered about in no regular pattern and be of irregular shapes and sizes.

3 likely sources of stone material used for the carving of jars

1. Stone boulders already at the jar site lying on the surface

2. Stone boulders lying on the surface at a remote location (a boulder field) such as at Phou Keng "Quarry"

3. Blocks of stone cut away from a larger mass of rock

The effort and tools needed for carving jars out of stone varies greatly between these 3 sources and it seems logical the carvers would have preferred using boulders already at a jar site since no transport is needed. When these are used up they would probably look for boulders at other places that could be carved and moved to the jar site and as a last resort make the big effort to cut blocks of stone away from a big mass, carve them into jars and transport them to the jar site.

When you visit Phou Keng "Quarry" you can see stone boulders lying on the surface that were partially carved into jars and never completed. It often looks like there was some fault line in the boulder that caused breakage during the carving or that the carver discovered the boulder was unsuitable to become a finished jar only after some wasted effort. It's just a ravine that had natural boulders lying about suitable for carving into jars. No large mass of rock is seen there where blocks of stone were cut out for removal.

The carving of jars from boulders lying where humans found them does provide an explanation of why some jars cannot yet be attributed to quarried stone and why some "missing" quarries may never be found. The surveyor James McCarthy who visited a jar site in 1884 and measured the largest jars is quoted as saying "these vessels are such as could not possibly have been carried to their present position but must have been made in situ". See our web page HERE for more of his comments.

Glacially-deposited Jars
The Author believes that some boulders (called glacial erratics) may have been brought down from the surrounding mountains in a prior Ice Age embedded in slowly moving rivers of ice and deposited to where they are now in moraine mounds (glacial debris deposits) when the ice melted (see examples HERE). Some of these boulders may have been partially buried in the finer glacial debris (glacial till) but became more exposed and ended up lying on top of the surface as this finer material washed away over time from rains.

Humans may have come by much later (possibly tens of thousands of years later) and wondered at this unique scene of big rounded boulders scattered about on hilltops with no clear source of where they came from or how they got there. Big rounded boulders like these are usually seen in low lying areas such as streambeds or at the base of a hill where they could have rolled down from. If there also happened to be a lake covering much of the PDJ at the time humans arrived some of these hilltops may have been islands in the the lake and the flatlands of the PDJ we see today would have been the bottom of that lake. This amazing scene of big boulders lying on islands in a lake may have seemed rather mystical and may havew inspired the custom of carving them into hollowed-out funeral jars.

Likely examples of jars carved from glacially-deposited boulders seem to be the jars found at the upper level of Site 1, Site 2, the outer-lying satellite areas of Site 3 and the scattered jars found along the walk path between Sites 2 & 3. It's also possible these naturally-situated boulders may have come to where they are by other geologic events but glacial deposition seems the most likely.

Former Lake at PDJ
A former lake that could have existed at the PDJ in former times may have been formed by an ice flow that temporarily blocked the single outlet river which drains the plain watershed but it could also have been a more permanent lake that was blocked by glacial debris left behind after the ice flow melted. (see map showing PDJ drainage and the single outlet HERE). There are ponds of water on the PDJ today that could be the remnants of a former lake. A good example is the low area near Ban Latsen at grid code MR190 on THIS MAP. See the map HERE for a hypothetical illustration of what areas a former lake may have covered at the PDJ. The depiction is based on elevation readings derived from Google Earth in 2014.

Sources of Ice Flows
It does seem that the PDJ is too far south to have been covered by large glacial ice sheets but it may have had smaller isolated ice flows such as those coming down from higher mountains on north-facing and tree-covered slopes. When visiting the areas around Jar Sites 1, 2 & 3 you can see in the surrounding hills for each site nearby higher mountains that could be the source of a former river of ice that could flow unimpeded to the jar site area. The higher areas of these source mountains are on average about 10 to 20 km distant from the sites and the elevation drop between their peaks and the jar sites ranges from 300 to 500 meters.

We can imagine a natural stream freezing over in a cold era and growing in size as it remains below freezing until this river of ice begins to move down plucking the rounded boulders from the streambed, carrying them down to the plain and dumping them in a moraine mound at the end of the ice flow. This river of ice may only have been a few meters thick and not very wide but sufficient to carry the boulders and other glacial till. All we need is a single cold era in the past at the PDJ to account for them.

There have been official Thai government tourism reports of prehistoric glacial activity at Phu Prabhat Park in Thailand which has left boulder fields. This area is south of PDJ and the boulder fields seem similar to those seen at Jar Site 2 and Site 16 near Mouang Khoun.

Moraine Mounds
Most of the hills or mounds that dot the PDJ seem scattered about in no pattern or logical scheme, just helter skelter. They don’t have ridges and gullies cascading down from their tops as most hills do after years of erosion. These mounds are just softly-rounded masses with some having faint concentric lines encircling them like the remnants of former terracing for crops.

If glacially-deposited boulders are theorized to have been on these mounds then the interior composition of the mounds should reveal glacial till, loose and inconsistent rounded rocks and finer clay materials. If these mounds have solid seams of rock or bedrock inside them or significant organic materials, it would refute a moraine theory.

Examples of terminal moraine mounds may be those arrayed in an arc ridge on both sides of Jar Site 2. The UXO-cleared path from Jar Site 2 to just north of Jar site 3 follows along this ridge going west. This arc shape may indicate the end of the ice flows as they changed courses annually, advancing and retreating seasonally and from year to year. It seems possible that all of the jars seen at the satellite (outer area) sites A, B, C & D at Jar Site 3 are on moraine mounds.

The jars at the satellite sites are very few in number and of varying sizes, with some uncarved smaller boulders lying among them. See a map HERE showing the location of Site 3 and it's satellite sites at map grid code NV200 and pictures HERE of the jars found at these sites. See the PDJ Mounds section of this website HERE for a more detailed discussion of these strange mounds and to view recent excavations that reveal the interior composition of them.

The illustration below shows possible sources and routes of rivers of ice that may have carried boulders to places where we find carved megalithic jars today. This is a very unscientific and speculative depiction based on the Author's personal observation and elevation readings.