Holocene paleointensity estimates of volcanic glass from the Big Island of Hawaii

Abstract:

Frequent volcanism on the Big Island of Hawaii allows researchers to take high-resolution measurements of ancient geomagnetic field intensity from lavas. Many laboratory and data analysis techniques are unable to consistently recover the intensity of lava flows erupted in known fields. Published paleointensity results from historic lava flows generally overestimate the expected field strength, suggesting that paleointensity data acquired from ancient lavas erupted in unknown fields are also biased high. A recent investigation of modern lavas on the Big Island of Hawaii was able to reproduce the expected field strength within 8% by collecting quenched volcanic material and applying strict selection criteria. We apply the same collection and analysis techniques to 67, ¹⁴C dated, lavas erupted during the last 10 ka on the Big Island and evaluate the long-term strength of the Holocene magnetic field in Hawaii. Preliminary results from our laboratory experiments show that 24 lava flows meet our rigorous selection requirements. The average field strength of these flows is 50.5 µT, a value substantially higher than the present day field (~36 µT), but similar to other paleofield estimates for the last few thousand years. Our methodology suggests that we can accurately recover the ancient field intensity, therefore we will compare the geomagnetic observations in our new dataset to previously published data from Hawaii, including some results from the same lava flows, and examine the differences in long-term field strength estimates, if any, between results with varying laboratory and sample collection techniques. This study will help constrain the variability of existing paleointensity results and offer an updated long-term field estimate for the Holocene in Hawaii.