On 19 December 2011 fishermen on the Red Sea reported seeing an eruption on Saba Island about 60 km to the southeast of Jebel Zubair Island, with lava fountains rising 20-30 m above the island. The same day the Ozone Monitoring Instrument (OMI) on the Aura satellite recorded a rise in Sulphur Dioxide (SO₂) levels above the southern Red Sea. The next day (20 December) the Moderate Resolution Spectroradiometer on the EOS Satellites detected a volcanic plume rising from a submarine eruption roughly 1.5 km southwest of Haycock Island, or 12 km northeast of Jebel Zubair. This is the first eruption in the Zubair Archipelago since at least 1846.
Satellite image of the plume near Jebel Zubair.
The Zubair Archipelago are a group of volcanic islands off the southwest coast of Yemen; they are essentially a shield volcano on the Red Sea Rift with a number of vents. A shield volcano is a broad, low profile volcano made up of successive layers of lava; it lacks the cone shape of a stratovolcano, but can grow far larger. The Hawaiian Islands are massive shield volcanoes, as are the vast volcanoes of Mars.
The Red Sea Rift is a spreading boundary between two tectonic plates, the African Plate and the Arabian, where new oceanic crust is being formed. Arabia was formerly part of the African Plate, but split away about 30 million years ago. The Great Rift Valley of Africa is a continuation of this rift, that is slowly splitting Africa in two from the north to the south.
Diagram showing a cross section through the rocks beneath the Red Sea.
The same rift system is also responsible for the nearby Jabal al-Tair volcanic island, which erupted unexpectedly in 2007, after 124 years of inactivity, killing 8 people, as well as the volcanoes of the Afar Triagle in Eritrea and Ethiopia and the volcanic fields of southern Yemen and Saudi Arabia.