magma
Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natural sa ...
tic activity in volcanically active regions. They may occur as a result of underthrusting of
hinterland
Hinterland is a German word meaning "the land behind" (a city, a port, or similar). Its use in English was first documented by the geographer George Chisholm in his ''Handbook of Commercial Geography'' (1888). Originally the term was associated ...
lithosphere
A lithosphere () is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust (geology), crust and the portion of the upper mantle (geology), mantle that behaves elastically on time sca ...
beneath a
volcanic arc
A volcanic arc (also known as a magmatic arc) is a belt of volcanoes formed above a subducting oceanic tectonic plate,
with the belt arranged in an arc shape as seen from above. Volcanic arcs typically parallel an oceanic trench, with the arc lo ...
, changes in
subduction
Subduction is a geological process in which the oceanic lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, the ...
parameters such as relative velocity, direction and
slab
Slab or SLAB may refer to:
Physical materials
* Concrete slab, a flat concrete plate used in construction
* Stone slab, a flat stone used in construction
* Slab (casting), a length of metal
* Slab (geology), that portion of a tectonic plate tha ...
dip (e.g.
flat slab subduction
Flat slab subduction is characterized by a low subduction angle (<30 degrees to horizontal) beyond the
), arc-arc collisions and subduction hinge advance. Individual magmatic lulls may last tens of millions of years between periods of volcanicity.
A volcanic gap is a magmatic lull that separates two distinct volcanic zones. For example, the
Andean Volcanic Belt
The Andean Volcanic Belt is a major volcanic belt along the Andean cordillera in Argentina, Bolivia, Chile, Colombia, Ecuador, and Peru. It is formed as a result of subduction of the Nazca Plate and Antarctic Plate underneath the South Americ ...
of
South America
South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the southe ...
has three major volcanic gaps: the Peruvian flat-slab segment (3 °S–15 °S), the
Pampean flat-slab
The Pampean flat-slab is the low angle subduction of oceanic lithosphere beneath Northern Argentina. The Pampean flat-slab is one of three flat slabs in South America, the other being the Peruvian flat-slab and the Bucaramanga flat-slab.
It is ...
segment (27 °S–33 °S) and the Patagonian Volcanic Gap (46 °S–49 °S).