Research press release


Nature Geoscience

Volcanism amid falling seas in the Mediterranean



Pietro Sternaiたちは、地質学的データと数値モデル化を組み合わせてこの考えを検証した。彼らはこの地域のマグマ貫入と火山噴火の時期に関する既存のデータを収集し、メッシニアン塩分危機の終わりに向かってパルス的に火山活動が増加したことを示している。研究者は、海水面がキロメートル規模で低下したことにより生じる地表荷重変化を、塩分濃度が極めて高い残った塩水と堆積した塩分の密度上昇による平衡錘を考慮に入れて計算した。彼らは数値モデルを用いて、海水面のそのような変化は荷重を取り除きマントルを減圧して、地中海の火山活動を増加させる引き金となるために十分であることを実証した。


関連するNews & Viewsの記事で、Jean-Arthur Oliveは、「この提案された関連性は、地中海地域の火山活動の時期により良い拘束条件を与える高分解能野外データを収集し、リソスフェアとマグマのダイナミクスを連結した革新的手法を開発するためのきっかけを与えるだろう」と述べている。

A fall in the level of the Mediterranean Sea about 6 million years ago may have triggered volcanic eruptions in the region, according to a study published online this week in Nature Geoscience.

Vast salt deposits exist beneath the Mediterranean seabed. These deposits are thought to have formed when the Mediterranean Sea became isolated from the Atlantic Ocean about 5 to 6 million years ago, leading to evaporation and sea-level fall in an event known as the Messinian salinity crisis. The rate and amount of sea-level fall in the Mediterranean during this time is debated. However, if the sea-level drop was dramatic and rapid, it could have unloaded Earth’s surface, decompressing the mantle below. Such mantle decompression can enhance magma production and, in turn, lead to volcanic eruptions at the surface.

Pietro Sternai and colleagues test this idea using a combination of geological data and numerical modelling. They compile existing data on the timing of magma intrusions and volcanic eruptions in the region, and show that there was a pulse of increased volcanic activity towards the end of the Messinian salinity crisis. The researchers calculate changes in the surface load caused by a kilometre-scale drop in sea level, taking into account the counter weight of the increased density of the remaining highly saline water and accumulating salt deposits. They then use a numerical model to verify that such changes in sea level would have been sufficient to unload and decompress the mantle, triggering increased volcanism in the Mediterranean.

The results provide independent support the idea that sea-level fall during the Messinian salinity crisis was rapid and occurred on a dramatic scale, and also highlight the sensitivity of Earth’s solid interior to changes at the surface.

In an accompanying News & Views article, Jean-Arthur Olive writes that “This proposed link will motivate the collection of high-resolution field data that better constrain the timing of volcanism in the Mediterranean, along with the development of novel approaches for coupled lithosphere-magma dynamics.”

doi: 10.1038/ngeo3032


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