The magma supply rate measures the production rate of magma at a volcano. Global magma production rates on Earth are about .

Definitions

Magma supply rate is also known as the Armstrong unit, where 1 Armstrong Unit = . Armstrong unit can also refer to volcanic flux rate per length of arc in discussions of volcanic arcs, in that case km2/year.

Sometimes in discussion of large volcanic systems such as volcanic arcs the volcanic flux rate is normalized to a surface area, similar to Darcy's law in hydrodynamics. It is often easier to measure magma supply rates when they are normalized for an exposed surface area as it is often difficult to delimit an intrusion.

Measurement difficulties

Estimating the volcanic flux rate or magma supply of a volcanic system is inherently difficult for a number of reasons, and different measurements can come to different conclusions about the volcanic flux rate of a given volcanic system. Not all volcanic bodies are equally well exposed, and it is often impossible or difficult to measure magma supply rates exactly. Furthermore, volcanic flux rates often vary over time, with distinct lulls and pulses. Wall rocks may be assimilated by magma or magma may undergo differentiation such as crystallization. Magma contains vesicles and volcanic edifices are often eroded. The sizes of volcanic edifices and plutons are difficult to estimate, especially in intrusions which are mostly buried.

Applications

The magma supply rate is used to infer the behaviour of volcanic systems which erupt periodically, as well as to describe the growth of the continental crust and of deep-seated magmatic bodies such as plutons. Magma output is usually larger in oceanic settings than in continental ones, and basaltic volcanic systems produce more magma than silicic ones.

Table of selected flux rates Name Rate Timespan Method Reference Aegina volcanic field Altiplano-Puna volcanic complex extrusive, intrusive 10 mya Total volume/Duration Altiplano-Puna volcanic complex, first pulse extrusive, intrusive 200 ka Total volume/Duration Altiplano-Puna volcanic complex, second pulse extrusive, intrusive 600 ka Total volume/Duration Altiplano-Puna volcanic complex, third pulse extrusive, intrusive 600 ka Total volume/Duration Altiplano-Puna volcanic complex, fourth pulse extrusive, intrusive 350 ka Total volume/Duration Altiplano-Puna volcanic complex, after 4th pulse extrusive, intrusive 2400 ka Total volume/Duration Arenal 7,000 years Total volume/Duration Aucanquilcha, Angulo 600-200 ka Total volume/Duration Aucanquilcha, Azufrera 1040–920 ka Total volume/Duration Aucanquilcha, Cumbre Negra Over 150 ka Total volume/Duration Aucanquilcha, Rodado 950–850 ka Total volume/Duration Aucanquilcha, edifice building phases Over 200 ka Total volume/Duration Aucanquilcha, later phases 800 ka Total volume/Duration Broken Ridge Between 88 and 89 million years ago Total volume/Duration Camargo volcanic field Total volume/Duration Caribbean large igneous province Between 89 and 91 million years ago Total volume/Duration Cascades A single pluton plumbing system Volume/Duration Central Volcanic Zone Last 28 million years Cerro Toledo, Jemez Caldera, intrusion Over 0.33 million years Magma supplied/duration Chimborazo A single pluton plumbing system Volume/Duration Chimborazo, Basal Edifice 120-60 ka Volume/Duration Chimborazo, Intermediary Edifice 60–35 ka Volume/Duration Chimborazo, Young Cone 33–14 ka Volume/Duration Cook Islands-Austral Islands 25 million years Total volume of edifices/age, neglecting subsidence and eroded material El Chichon Past 8,000 years Volume/Duration El Hierro > Juvenile stage Total volume including sector collapses/Duration El Misti Last 350 ka Total volume/Duration Emperor Seamounts 80 to 45 million years ago Volume/Duration Farallon Negro Interpolated volume/Duration Hawaii Volume including subsidence/Duration Hawaiian Islands 6 to 0 million years ago Volume/Duration Hawaiian Ridge 45 to 0 million years ago Volume/Duration Imbabura Past 35,000 years Minimum total volume/Duration Klyuchevskaya Sopka Last 6800 years Total volume/Duration Lesser Antilles Volcanic Arc Last 100 ka Total volume/Duration Marquesas Islands 7 million years Total volume of edifices/age, neglecting subsidence and eroded material Meidob volcanic field, whole edifice Between 7 and 0.3 million years ago Total volume/Duration Menengai Methana Morne Jacob, whole edifice During, 3.7 ± 0.03 Myr Total volume/Duration Morne Jacob, J1T 5.14 ± 0.07 and 4.10 ± 0.06 Ma Total volume (assuming basis at sea level)/Duration Morne Jacob, J2T Between 3.2 and 1.5 Ma Total volume (subtracting J1T)/Duration Mount Adams volcanic field Postglacial Mount Etna 330,000 years Estimated volume/timespan Mount Etna, Timpe phase 110,000 years Estimated volume/timespan Mount Etna, Valle del Bove phase 50,000 years Estimated volume/timespan Mount Etna, Stratovolcano phase 60,000 years Estimated volume/timespan Mount Etna Based on the carbon dioxide output Mount Pelee, Mont Conil Ia ±0.01 543±8-189±3 ka Edifice volume/Duration Mount Pelee, Mont Conil Ib ±0.09 Edifice volume/Duration Mount Pelee, Paleo-Pelee ±0.08 126±2–25 ka Edifice volume/Duration Mount Pelee, Saint Vincent stage ±0.20 25–9 ka Edifice volume/Duration Mount Pelee, longterm Edifice volume/Duration Mount Pelee Past 13,500 BP Average eruption volume*Eruptions per lifespan Mount Sidley Nevado Tres Cruces 1.5-0.03 mya Volume/Duration Parinacota Since Late Pleistocene. Volume/Duration Parinacota Last 8,000 years. Volume/Duration Parinacota, Young Cone prior to 8.1 ka 1000–2000 years long. Ruapehu 250,000 years Total volume/Lifespan Ruapehu, Mangawhero formation Ruapehu, Te Herenga formation Ruapehu, Waihianoa formation Ruapehu, Whakapapa formation Samoa 3 million years Total volume of edifices/age, neglecting subsidence and eroded material San Francisco Mountain ≤ 400 ka Total volume/Duration, including landslide removals San Francisco Mountain, main shield building stage ~ 100 ka Total volume/Duration, including landslide removals San Pedro de Tatara Total volume/Duration, including glacially eroded volumes Santa Maria 103-35 ka Santa Maria 103 ka – 1902 Sierra Nevada A single pluton plumbing system Volume of plutons/emplacement time Society Islands 5 million years Total volume of edifices/age, neglecting subsidence and eroded material Soufrière Hills Last 174 ka Total volume/Duration Stromboli Magma intrusion needed to create the measured sulfur dioxide emissions. Tancítaro ≤ ≥ 550 ka Total volume/Duration Tenerife Long term average Total volume/Duration Tenerife, Old Basaltic Series 8-4 million years ago Estimated volume/Duration Tenerife, Cañadas I volcano 1 million years Estimated volume/Duration Tenerife, Cañadas II volcano 0.8 million years Estimated volume/Duration Tenerife, Cordillera Dorsal 0.2 million years Estimated volume/Duration Tenerife, Teide-Pico Viejo 0.2 million years Estimated volume/Duration Tunupa-Huayrana 240,000–90,000 years Ubinas < 376 ka Cone volume/Duration Yellowstone Long term average

References