Between January and February 1811 a prolonged period of seismic activity affected the settlements to the extreme southwest of São Miguel, in particular in the parishes of Ginetes and Mosteiros.

[1] The next morning, 13 June, HMS Sabrina landed in Ponta Delgada as Tillard had a pre-appointed meeting with William Harding Read, British consul general to the Azores.

Read informed Tillard of the multiple earthquakes felt on São Miguel, especially in Ginetes and Mosteiros, which had caused panic among the island's residents.

Tillard, even more enthusiastic, sailed HMS Sabrina toward the eruption area on the night of 15 June, but weak winds still kept him from approaching as closely as he hoped.

In an area where Sabrina's crew had previously measured a depth of 40 fathoms (240 ft; 73 m), they now observed rock formations just below the water's surface, as well as constant emission of ash and steam.

The following day, 19 June, Sabrina Island had grown to an estimated altitude of 20 metres (66 ft) above sea level and measured approximately 1 kilometre (0.62 mi) in diameter.

Despite being 5 kilometres (2.7 nmi; 3.1 mi) away from the island, Sabrina became covered in fine black ash and water thrown into the air by the eruption.

The ensuing four-way territorial dispute between Great Britain, France, Spain, and the Kingdom of the Two Sicilies ultimately resolved as the Sabrina Island conflict had.

At its largest, Sabrina Island was a circular volcanic cone with a perimeter of 2 kilometres (1.2 mi) and an altitude between 90 and 100 metres (300 and 330 ft) above sea level.