Dating lava flows for paleomagnetic

Key flows of unknown age are dated by comparison with the history of variation, and relative ages of other flows are determined from super position and vegetation development.

Paleomagnetic dating precision varies with time and depends uponthe rate of secular variation and dispersion in the data.

Kilauea's past behavior has varied in space and time.

The chief spatial variation is a decrease in typical eruption duration at increasing distances away from the summit magma reservoir.

Dating precisions are about 100 years during the past 500 years and about 250 years during the preceding millenium.

Precision should be increased to a few decades by reducing the dispersion, refining the history of variation, and adding paleomagnetic intensity to the record of variation.

However, at high-latitude volcanic islands, the paucity of soils severely limits C age determinations, refers to layers that rarely lie directly above lava flows to be dated.Type A eruptions last hours to days and leave open eruptive fissures and commonly a single lava flow consisting of surface-fed pahoehoe and aa.Type B eruptions last for days to weeks and produce pyroclastic central vents and multiple flows of surface-fed pahoehoe and aa.Other variations appear to be peculiar to particular localities.Changes have occurred over intervals of decades and centuries; some have been repeated and some may have occurred in evolutionary sequences.

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