BBC:
A researcher in New Zealand is searching for abandoned Maori
steam ovens, called hangi, in order to gather data on Earth's
magnetic field. Gillian Turner of Victoria University in
Wellington spoke at the
annual meeting
of the American Geophysical Union, held this week in San
Francisco. The ovens, which date back to about AD 1200, were
pits in the ground filled with stones that were heated to very
high temperatures for cooking food. The stones the Maori used
tended to have a high concentration of magnetite, which became
demagnetized as they were heated past their Curie temperature.
As they cooled, they became remagnetized in the direction of
the local field, writes Jonathan Amos for the BBC. Using
radiocarbon analysis of the charcoal left by the firewood
burned, Turner and her team are working to gather data on
Earth's magnetic field in the South Pacific from the past 800
years. Her ultimate goal is to gather data that covers the past
10 000 years, but to go deeper in time, she will need to find
other sources, such as volcanic rocks and lake sediments.
