An ancient tree has been found in New Zealand, in the growth rings of which the variability of Earth's magnetic field can be "read". The kauri tree (as it is called by the Māori), or Agathis australis, was located on New Zealand's North Island. It was accidentally discovered by workers operating an excavator while expanding a geothermal power plant. The tree trunk was located about 26 feet underground, with a diameter of about 8 feet and a length of 65 feet. Carbon dating "revealed" that the tree "lived" for about 1,500 years – in the period approximately 42,500 to 41,000 years ago.