Geology Reference
In-Depth Information
to as Thanatia, for exergy calculations. Thanatia is a degraded planet where all
mineral resources have been depleted and all fossil fuels burnt. It is composed of
a crepuscular atmosphere, hydrosphere and upper continental crust, which were
modelled with the help of mathematical algorithms based on current geological and
geochemical information.
The chapter has emphasised the importance of gathering knowledge of the de-
graded planet, since it is this that will allow a thorough assessment of the current
natural endowment on Earth and the velocity at which humankind is degrading its
resources. Both factors are essential for e
cient management of minerals and in
short, for slowing down the rate at which Man is approaching the “commercial end”.
The proposed crepuscular atmosphere has a carbon dioxide content of 683 ppm,
a mean surface temperature of 17.2
o
C, a pressure of 1.021 bar and a composition
on a volume basis of 78.8% N
2
, 20.92% O
2
, 0.93% Ar, and 0.0015% of trace gases.
However, as shown in Table 10.3 before these conditions are reached, atmospheric
temperature could increase up to 3.76
o
C and CO
2
concentrations of 731 ppmv
might be experienced. In the same way, in the very long term (after two millen-
nia), atmospheric temperature and CO
2
concentration would stabilise to an average
surface temperature of 15.3
o
C and a CO
2
concentration of 439 ppm.
Considering that saline water accounts for 97.5% of the whole hydrosphere, the
crepuscular hydrosphere is assumed to have the current chemical composition of the
oceans as shown in Table 5.5 but at the average temperature of around 17
o
C.
For Thanatia's upper continental crust, the authors have proposed a model based
on Grigor'ev's preliminary mineralogical composition but with the improvement of
ensuring a chemical coherence between species and elements. The resulting crust
is composed of 292 minerals. This preliminary model (that is subject to improve-
ments) provides the starting point of a new baseline, which will allow for the exergy
calculation of mineral resources.
This chapter has also identified the differences between the most commonly
used R.E. in the calculation of chemical exergies and the baseline presented in the
Crepuscular Earth Model, since both approaches are required for assessing the loss
of the mineral endowment on Earth.
At this point the authors would like to reiterate the fact that reaching the state
of Thanatia (a highly improbable event) does not imply the end of life on Earth,
even if it would likely entail important changes in the biosphere. It only implies
the commercial end of the planet, where non-renewable resources are no longer
available in a concentrated form. A scenario that should only occur if mankind
fails to undertake any effective search and alternative means of development, which
could include the mass use of other non-climate affecting energy sources and the
closure of material cycles.
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