Geoscience Reference
In-Depth Information
12
10
H
2
supply
8
6
H
2
demand
4
2
0
0
500
1000
1500
2000
2500
3000
3500
4000
4500
Age (millions of years)
Figure 8.4. Dick Holland's calculations of the hydrogen flux from the mantle versus rates of
oxygen liberation to the atmosphere. Black dots indicate crossing points for two different
model scenarios. see text for details. Data taken from Holland (2009).
between the surface environment and the interior of Earth is just too
important to ignore. Dick Holland also recognized the importance of
this connection and made his stab at predicting the history of H
2
flux
from Earth's interior through time. This estimate is shown in
igure 8.4
with two lines that represent Dick's view on the range of uncertainty in
the calculation.
Dick also took a stab at predicting the potential rates of oxygen pro-
duction through organic carbon and pyrite burial through time.
8
I will
not go into the details of this calculation here,
9
but the results are also
presented in
igure 8.4.
In reading this graph, focus on the two black
dots, not all of the overlapping grey. These dots should be viewed as the
extremes of the calculation. hat we see is pretty illuminating. Dick's
modeling suggests that sometime between about 2.0 and 2.7 billion years
ago, rates of oxygen liberation first exceeded rates of oxygen demand.
This figure provides a graphic explanation for the cause of the GOE.
Is this really the way it happened? I'll stick my neck out and say, “I
think so,” at least in broad detail. This just makes too much sense. To be
fair, others have had similar ideas, notably Jim Kasting (from
chapter 1)
