The archaeologist would have to decide which one is the most likely based on other indicators such as finds or radiocarbon dates.
Magnetic particles are always oriented towards the magnetic north pole, and this is fixed at the time of burning.
When structures are repeatedly burnt, we can sometimes measure the date of separate burning episodes by sampling different fired layers.
Archaeomagnetic dating is based on the comparison of directions, intensities or polarities with master records of change.
Archaeomagnetic direction and archaeointensity dating are regional pattern-matching techniques, whereas magnetic reversal dating is a global pattern-matching method.
Magnetism occurs whenever electrically charged particles are in motion.
The Earth's molten core has electric currents flowing through it.The term that refers to changes in the Earth's magnetic field in the past is paleomagnetism.Any changes that occur in the magnetic field will occur all over the world; they can be used to correlate stratigraphic columns in different locations.This correlation process is called magnetostratigraphy. Lava, clay, lake and ocean sediments all contain microscopic iron particles.When lava and clay are heated, or lake and ocean sediments settle through the water, they acquire a magnetization parallel to the Earth's magnetic field.These differences in magnetic orientation, which can give us an accurate date, are compared to a known curve of the movement of the earth's magnetic pole.