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the other hand between those components and life forms that
constitute them (flux due to the metabolisms of life forms). The
objective of this chapter is to describe these interactions.
1.1.4.
The major components of the Earth system
The general physics and biogeochemistry of the Earth system show
that the most important internal fluxes of matter and energy only
occur within a few particular interfaces. The interface that separates
the “solid” Earth from external envelopes of fluids (the ocean and the
atmosphere) is found at the location of volcanic emissions, erosion,
sedimentation and the subduction of tectonic plates. The interface
between the ocean and the atmosphere gives rise to evaporation,
precipitation and exchanges of gas. The interface between the
continents and oceans is the location of transfer of continental matter
eroded into the oceans, in particulate and dissolved forms, that partly
fuels the sedimentation of the oceans.
A simplified but pertinent description of the Earth system therefore
consists of defining the internal “base” components through a few
very large compartments (or reservoirs), which include the geosphere,
ocean and atmosphere. They are like the vital organs of an animal
between which fluxes of matter and energy travel. In this sense, they
are physical compartments, whose role in the Earth system is
“organic”.
Improvements in our knowledge of these compartments, through
active research over the last few decades, have, of course, led to the
refinement of the understanding of the system. It is in this way that we
are able to make distinctions between the different reservoirs of water
on earth (the hydrosphere) - the oceans, continental fresh water, ice
and water vapor. However, further distinctions between
subcompartments have proven to be necessary. For example, the
ocean's surface and its interior do not have the same physical
properties and are separated by a discontinuity in temperature (the
thermocline) but also a discontinuity in density. These two
subcompartments exchange matter and energy between themselves
(via thermohaline oceanic convection and turbulence in the
