Research press release


Nature Geoscience

Bursting the bubble on the volcanic gas-magma relationship



Clive Oppenheimerたちは、ハワイの活火山であるキラウエアから放出されるガスの組成を、2013年の、脱ガスが穏やかな時期と活発な時期の両方について測定した。その結果、ガスの泡が地表に向けて上昇して大きくなると、温度が下がってガスの内側はマグマとの接触を失い、これによってガスの組成が急速に変化することが明らかになった。しかし、火山ガスの監視に基づいた災害と危険度の評価は、比較的長い時間にわたって平均化されたガスの組成に依拠している。Oppenheimerたちは、このように時間で平均化することで、災害評価の要因に含めるべき火山の振る舞いや脱ガスの力学的性質といった重要な情報が失われる可能性がある、と示唆している。

The link between magma and gases that rise out of volcanoes might be more complicated than previously thought, with the gas composition changing as it cools, reports a paper published online this week in Nature Geoscience. The findings may impact volcanic monitoring efforts, as gases injected into the atmosphere during eruptions are used to yield information about the magma source and the nature of volcanic activity.

As magma rises through a volcano towards the Earth’s surface its pressure decreases. This causes the gases dissolved in the magma to be released as bubbles. As the composition of the magma and volcanic gases are linked, studying the composition of one shines light on the other. The link, however, may be more complicated than previously thought.

Clive Oppenheimer and colleagues measured the composition of gases released from Kilauea, an active volcano in Hawaii, during periods of both gentle and more vigorous degassing in 2013. They find that when the gas bubbles rising to the surface get large, they cool down and the gas inside loses contact with the magma, resulting in rapidly changing gas compositions. Hazard and risk assessments based on the monitoring of volcanic gases, however, are based on gas compositions averaged over relatively long periods of time. The authors suggest that this time averaging may be missing important information about volcanic behaviour and the dynamics of degassing that should be factored into hazard assessments.

doi: 10.1038/s41561-018-0194-5


メールマガジンリストの「Nature 関連誌今週のハイライト」にチェックをいれていただきますと、毎週各ジャーナルからの最新の「注目のハイライト」をまとめて皆様にお届けいたします。