Bradyseism is the gradual uplift (positive bradyseism) or descent (negative bradyseism) of part of the Earth's surface caused by the filling or emptying of an underground

magma chamber A magma chamber is a large pool of liquid rock beneath the surface of the Earth. The molten rock, or magma, in such a chamber is less dense than the surrounding country rock, which produces buoyant forces on the magma that tend to drive it up ...

or hydrothermal activity, particularly in volcanic

calderas A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is ...

. It can persist for millennia in between eruptions and each uplift event is normally accompanied by thousands of small to moderate

earthquakes An earthquake (also known as a quake, tremor or temblor) is the shaking of the surface of the Earth resulting from a sudden release of energy in the Earth's lithosphere that creates seismic waves. Earthquakes can range in intensity, fro ...

. The word derives from the

ancient Greek Ancient Greek includes the forms of the Greek language used in ancient Greece and the ancient world from around 1500 BC to 300 BC. It is often roughly divided into the following periods: Mycenaean Greek (), Dark Ages (), the Archaic pe ...

words βραδύς ''bradús'', meaning "slow", and σεισμός ''seismós'' meaning "movement", and was coined by

Arturo Issel Arturo Issel (Genoa April 11, 1842 – Genoa November 27, 1922) was an Italian geologist, palaeontologist, malacologist and archaeologist, born in Genoa. He is noted for first defining the Tyrrhenian Stage in 1914. Issel was also renowned at th ...

in 1883.

Phlegraean Fields

The area of

Phlegraean Fields The Phlegraean Fields ( it, Campi Flegrei ; nap, Campe Flegree, from Ancient Greek 'to burn') is a large region of supervolcanic calderas situated to the west of Naples, Italy. It was declared a regional park in 2003. The area of the c ...

(Campi Flegrei), near

Naples Naples (; it, Napoli ; nap, Napule ), from grc, Νεάπολις, Neápolis, lit=new city. is the regional capital of Campania and the third-largest city of Italy, after Rome and Milan, with a population of 909,048 within the city's adm ...

, is a collapsed

caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is ...

, namely a volcanic area formed by several volcanic edifices, which includes the Solfatara volcano, well known for its

fumaroles A fumarole (or fumerole) is a vent in the surface of the Earth or other rocky planet from which hot volcanic gases and vapors are emitted, without any accompanying liquids or solids. Fumaroles are characteristic of the late stages of volcan ...

. The Campi Flegrei area is especially noted for bradyseismic uplift and subsidence. The

inflation In economics, inflation is an increase in the general price level of goods and services in an economy. When the general price level rises, each unit of currency buys fewer goods and services; consequently, inflation corresponds to a reduct ...

and deflation of this caldera is especially well documented due to its seaside location and a long history of habitation and construction in the area. In particular, the town of Pozzuoli features the Roman

Macellum of Pozzuoli The Macellum of Pozzuoli ( it, Macellum di Pozzuoli) was the macellum or market building of the Roman colony of Puteoli, now the city of Pozzuoli in southern Italy. When first excavated in the 18th century, the discovery of a statue of Serapis ...

in which three marble columns show bands of boreholes or ''

Gastrochaenolites ''Gastrochaenolites'' is a trace fossil formed as a clavate (club-shaped) boring in a hard substrate such as a shell, rock or carbonate hardground. The aperture of the boring is narrower than the main chamber and may be circular, oval, or dumb- ...

'' left by marine ''

Lithophaga ''Lithophaga'', the date mussels, are a genus of medium-sized marine bivalve molluscs in the family Mytilidae. Some of the earliest fossil ''Lithophaga'' shells have been found in Mesozoic rocks from the Alps and from Vancouver Island.Ludvigsen, ...

'' molluscs. These occur up to 7 metres up the columns, showing how bradyseism in the area lowered the land to at least this depth under the sea and subsequently raised it again. More recently, between 1968 and 1972, the Campi Flegrei area suffered an episode of positive bradyseism and rose by 1.7 metres. Another rise of 1.8 metres occurred between 1982 and 1984. This correlated with a shallow (4 km deep)

earthquake swarm In seismology, an earthquake swarm is a sequence of seismic events occurring in a local area within a relatively short period. The time span used to define a swarm varies, but may be days, months, or years. Such an energy release is different f ...

during the same period, which led to the evacuation of 30,000 people due to the perceived risk of imminent eruption.

References

{{Reflist Geomorphology Volcanology Seismology