Dom João de Castro Bank is a large submarine volcano

Submarine volcano

Submarine volcanoes are underwater fissures in the Earth's surface from which magma can erupt. They are estimated to account for 75% of annual magma output. The vast majority are located near areas of tectonic plate movement, known as ocean ridges...

 in the Azores

Azores

The Archipelago of the Azores is composed of nine volcanic islands situated in the middle of the North Atlantic Ocean, and is located about west from Lisbon and about east from the east coast of North America. The islands, and their economic exclusion zone, form the Autonomous Region of the...

 in the central Atlantic Ocean

Atlantic Ocean

The Atlantic Ocean is the second-largest of the world's oceanic divisions. With a total area of about , it covers approximately 20% of the Earth's surface and about 26% of its water surface area...

. The volcano lies midway between the islands of Terceira and São Miguel

São Miguel

-Brazil:* São Miguel, Brazil, Rio Grande do Norte* Barra de São Miguel, Alagoas, a municipality in the State of Alagoas* Barra de São Miguel, Paraíba, a municipality in the State of Paraíba* São Miguel do Aleixo, a municipality in the State of Sergipe...

 and rises to within 14 m (46 ft) of the sea surface. The volcano has a large fumarole

Fumarole

A fumarole is an opening in a planet's crust, often in the neighborhood of volcanoes, which emits steam and gases such as carbon dioxide, sulfur dioxide, hydrochloric acid, and hydrogen sulfide. The steam is created when superheated water turns to steam as its pressure drops when it emerges from...

 field and remains seismically active.

It last erupted in December 1720, forming an island of 1.5 kilometre (0.93205910497471 mi) in length and about 250 m (820.2 ft) in altitude. It remained above sea level for only two years, before rapid erosion

Erosion

Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...

 reduced its height.

Two parasitic craters, both about 90 x 45 m (300 x 150 ft) wide, are located on the northwest flank. The younger crater displays a floor consisting of a chilled lava lake

Lava lake

Lava lakes are large volumes of molten lava, usually basaltic, contained in a volcanic vent, crater, or broad depression. The term is used to describe both lava lakes that are wholly or partly molten and those that are solidified...

 with polygonal surface fractures, while the older, less distinct crater is obscured by tephra

Tephra

200px|thumb|right|Tephra horizons in south-central [[Iceland]]. The thick and light coloured layer at center of the photo is [[rhyolitic]] tephra from [[Hekla]]....

 deposits.

Don João de Castro is an important fishing ground for both demersal fish, such as the black seabream

Black seabream

The Black Seabream is a species of Sparidae fishes. They are recognisable by their oval compressed body and jaws containing 4-6 rows of slender teeth which are larger at the front. They are silvery in colour with blue and pink tinges and broken longitudinal gold lines...

 (Spondyliosoma cantharus) and blackbelly rosefish, (Helicolenus dactylopterus), as well as pelagic tuna

Tuna

Tuna is a salt water fish from the family Scombridae, mostly in the genus Thunnus. Tuna are fast swimmers, and some species are capable of speeds of . Unlike most fish, which have white flesh, the muscle tissue of tuna ranges from pink to dark red. The red coloration derives from myoglobin, an...

species (Thunnus and others).