The large green stain is clearly visible in the image to the right, taken on Oct. 13 by NASA’s Aqua satellite.
When the spacecraft passed over the region at 3:45 p.m. local time, the plume was streaming southwestward from the vents, located just off El Hierro’s southern tip.
Aircraft and boats have been advised to steer clear of the the area above the source of the plume — a zone of bubbling and upwelling that has killed fish and contains potentially hazardous gases.
Video of the water around the plume's source was released by the Canary Island government.
Volcanologists said it appeared the eruptions were slowly drifting toward El Hierro, but it could create a new island if it continued offshore for a long period of time.
Government scientific coordinator Ramon Ortiz said that should the eruptions reaches shallower water, the surface will start to steam, followed by explosions that could eventually build a new island.
The eruptions followed an unprecedented series of more than 10,500 volcanic tremors around El Hierro since July 17.
The frequency and intensity of those tremors have undergone a significant decrease since the new submarine vent began to spew.
El Hierro experienced its only eruption in recorded history in 1793, when one crater spewed for about a month.
Image: NASA MODIS Rapid Response System