Publication Date:
2020-02-24
Description:
The principle of carbon-14 dating is well known (1): the content of this radioisotope in a sample
of an animal or a plant origin is assessed and the time elapsed from the formation of the organic
material to the moment of assessment is calculated comparing the present content of carbon-
14 to that at the time the plant or animal was alive. This last is assumed at equilibrium with
the atmospheric concentration of carbon-14, which, in turn, is assumed to have been constant
through the ages. Knowing the decay constant of carbon-14, the time elapsed is deduced. Then this
calculated age is entered in calibration diagrams that account for the actual variable atmospheric
content through the years, to obtain the age of the sample, or more precisely, a time interval in
which the age falls. Thus, the main idea behind the technique is that the atmospheric concentration
of carbon-14 marked CO2 is essentially constant, or slowly variable, from year to year. To this, one
word of caution needs be added: after WW2, and particularly from the 1950s, the concentration
of carbon-14 in the atmosphere has become quite erratic due to nuclear weapon tests, and hence
this technique is not used for dating samples from that time on.In the present work, the whole carbon-14 idea has been reused in a somewhat different context,
and with a different purpose in mind.Afact to be kept in mind is thatCO2 contained in vast amounts
within the Earth’s crust beneath the volcanic apparatus, the so-called fossil CO2, either degassed
by the mantle or having been formed by metamorphic reactions in the crust, contains no trace
of the carbon-14 isotope. Fossil CO2 release is often associated to seismic and volcanic activity:
the question may then arise whether, on occasion of such major releases and in the presence of
landscape conformation conducive to slow mixing (narrow valley bottoms, canyons, and the like),
the carbon-14 contents of local vegetation may be affected by the presence of spent CO2. The
Solfatara at Pozzuoli presented both the above-mentioned conditions: it has the required shape
and it has endured large releases of fossil CO2 in the early 1980s. It presented itself as an ideal
location to test this hypothesis. There are pine trees planted in the 1930s, as part of a reforestation
plan: it was possible to select two recently dead trees, one in the Solfatara area and presumably as
affected by the CO2 release as could be possible, and the other immediately outside and upwind
of the area, constituting an ideal blank. Sections were taken from the two trees and analysed to
determine the carbon-14 content of several rings corresponding to the years of interest. In the
following sections, the method and the results will be presented and commented upon.
Description:
Published
Description:
376–381
Description:
1.2. TTC - Sorveglianza geochimica delle aree vulcaniche attive
Description:
1.4. TTC - Sorveglianza sismologica delle aree vulcaniche attive
Description:
2.4. TTC - Laboratori di geochimica dei fluidi
Description:
4.5. Studi sul degassamento naturale e sui gas petroliferi
Description:
JCR Journal
Description:
reserved
Keywords:
radiocarbon
;
seismicity
;
degassing
;
fossil CO2
;
dendrochronology
;
03. Hydrosphere::03.04. Chemical and biological::03.04.05. Gases
;
03. Hydrosphere::03.04. Chemical and biological::03.04.06. Hydrothermal systems
;
04. Solid Earth::04.01. Earth Interior::04.01.01. Composition and state
;
04. Solid Earth::04.04. Geology::04.04.11. Instruments and techniques
;
04. Solid Earth::04.04. Geology::04.04.12. Fluid Geochemistry
Repository Name:
Istituto Nazionale di Geofisica e Vulcanologia (INGV)
Type:
article
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