Since the pole has wandered over time, comparing the alignment of the iron mineral particles to the master curve of the North Pole provides a usable date for reference. Howard 1991 Direct dating of prehistoric canal sediments using archaeomagnetism. The archaeological dating technique of archaeomagnetic dating was introduced to the field of archaeology in the 1960s by researcher Robert Dubois. The younger one was emitted in 1870 and used to validate the method, while the older one known as Ceboruco flow is of unknown age but probably younger than ∼1005 AD and older than 1528 AD.Each flow was sampled in at least four sites, in order to unravel between site variations.For the 1870 flow, between site differences were notable and additionally post-cooling block movements were important; therefore, two sites had to be rejected.Three sites from the vent area and one at the tip of the 1870 flow provided well-constrained directions.
On the earth's surface, when you hold a compass and the needle points to north, it is actually pointing to magnetic north, not geographic (true) north.
The Earth's magnetic north pole can change in orientation (from north to south and south to north), and has many times over the millions of years that this planet has existed.
The term that refers to changes in the Earth's magnetic field in the past is paleomagnetism.
This is also true for Ceboruco lava flow, and overall mean directions and palaeointensities were then used for palaeomagnetic dating applying the Matlab tool and the global palaeosecular variation model SHA. For the 1870 lava flow, the dating resulted in an age ranging between 17 AD (95 per cent probability level), which includes the real emplacement age.
In addition, the Ceboruco lava flow was dated between 10 AD, which is close to the large plinian Jala eruption producing the crater of Ceboruco volcano around 1005 AD.