Abstract. Basalt weathering is one of many relevant processes balancing the global
carbon cycle via land–ocean alkalinity fluxes. The CO2 consumption by
weathering can be calculated using alkalinity and is often scaled with
runoff and/or temperature. Here, it is tested if the surface age distribution
of a volcanic system derived by geological maps is a useful proxy for
changes in alkalinity production with time. A linear relationship between temperature normalized alkalinity fluxes and
the Holocene area fraction of a volcanic field was identified using
information from 33 basalt volcanic fields, with an r2=0.93. This
relationship is interpreted as an aging function and suggests that fluxes
from Holocene areas are ∼10 times higher than those from old
inactive volcanic fields. However, the cause for the decrease with time is
probably a combination of effects, including a decrease in alkalinity
production from material in the shallow critical zone as well as a decline
in hydrothermal activity and magmatic CO2 contribution. The addition of
fresh reactive material on top of the critical zone has an effect in young
active volcanic settings which should be accounted for, too. A comparison with global models suggests that global alkalinity fluxes
considering Holocene basalt areas are ∼60 % higher than the
average from these models imply. The contribution of Holocene areas to the
global basalt alkalinity fluxes is today however only ∼5 %,
because identified, mapped Holocene basalt areas cover only ∼1 %
of the existing basalt areas. The large trap basalt proportion on the
global basalt areas today reduces the relevance of the aging effect.
However, the aging effect might be a relevant process during periods of
globally intensive volcanic activity, which remains to be tested.
Feasibility to Use Continuous Magnetotelluric Observations for Monitoring Hydrothermal Activity. Numerical Modeling Applied to Campi Flegrei Volcanic System (Southern Italy)
