Abstract
Accurately estimating the paleomagnetic field intensity recorded in terrestrial and planetary materials is the key to understanding dynamo processes. Thellier‐series stepwise‐heating methods with partial thermoremanent magnetization (pTRM) checks for alteration are considered the most reliable technique even though pTRM checks are shown to be incapable of detecting the entirety of thermal alteration. We utilize a recently developed multidomain‐correction experiment (or RESET) to monitor thermally induced magnetic property alteration that may happen to the very specimen used in Thellier‐series experiments. We also use rock magnetic property changes to track the physicochemical alteration of fresh companion specimens of Galapagos lavas that were previously used for paleointensity determinations. Our results show that laboratory heating induced thermal alteration of a typical Galapagos lava sample starts to occur at around 500°C. It escaped detection by pTRM checks but was caught by our RESET method.