the organic carbon forming animal tissues. Also sulfur dioxide (SO 2 ) is added to
the atmosphere due to biological activity in seawater.
The oceans are the major reservoir for carbon storage ([4 9 10
13 tons) while
the atmosphere has much less (8 9 10
9 tons). The study of ocean water circulation
is a difficult task because the time of mixing between different water masses is
longer (thousands of years) than in the atmosphere. Thus the study of the water
masses and the input of gaseous phases inside the ocean is a vital issue for
humanity in order for us to understand and eventually prevent pollution and the
green house effect.
Because of the numbers of their atoms and their lattice configuration, gases
such as CO 2 and H 2 O have a larger capacity for retaining the infrared rays from the
sun than do oxygen and nitrogen. The equilibrium between them will be perturbed
if the concentration of these gaseous phases is modified. It appears that for about a
century this equilibrium has been being modified because of the massive introduction of CO 2 into the atmosphere due to human activities. However, the ocean
has the capacity to absorb a large quantity of carbon from the atmosphere in the
form of organic material, which can be stored away from the atmosphere in
sediment for long geological periods. However, in subaerial regions the various
forms of carbon compounds will stay in contact with the atmosphere and might
influence climate change.
Formation of Continents
The Earth is in constant motion and has continued to change since its creation 4.7
billion years ago. Some of this evolution is witnessed during a human’s lifetime,
such as when volcanic eruptions, earthquakes or tsunamis disrupt daily activities
or create major catastrophes.
It is difficult to draw the shape of early-formed continents. When the molten
Earth solidified, solid crust started to form isolated pieces of landmass called
‘‘cratons’’. The cratons are thick portions of today’s continent formed from older
pieces of continents. The oldest rock formations or cratons exposed on the surface
of the Earth are Archean in age (3.8–4.4 billion years and older) (Myers and
Crowley 2000). Archean (2,500 million years ago) rocks have been seen in
Greenland, on the Canadian Shield, in Western Australia, and in South Africa.
These first continental-size land mass are also called ‘‘Ur’’ (Hazen 2012). At the
beginning of Earth’s creation, there were no solid landmasses until late in the
Archean period, when small ‘‘proto-continents’’ were formed. These proto-continents probably formed as ‘‘patchy hotspots’’ during the cooling and differentiation
of the ‘‘magma ocean’’ giving rise to mafic and felsic rocks.
The world’s oceans have probably existed from the beginning of our planet’s
history. Evidence suggesting the presence of ancient oceans has been gathered from
the discovery of metamorphosed sedimentary rocks from Canada and Australia
(Wilde et al. 2001). Sediments containing fossils are deposited on the sea floor and
36
2 Our Haven, Planet Earth
the atmosphere due to biological activity in seawater.
The oceans are the major reservoir for carbon storage ([4 9 10
13 tons) while
the atmosphere has much less (8 9 10
9 tons). The study of ocean water circulation
is a difficult task because the time of mixing between different water masses is
longer (thousands of years) than in the atmosphere. Thus the study of the water
masses and the input of gaseous phases inside the ocean is a vital issue for
humanity in order for us to understand and eventually prevent pollution and the
green house effect.
Because of the numbers of their atoms and their lattice configuration, gases
such as CO 2 and H 2 O have a larger capacity for retaining the infrared rays from the
sun than do oxygen and nitrogen. The equilibrium between them will be perturbed
if the concentration of these gaseous phases is modified. It appears that for about a
century this equilibrium has been being modified because of the massive introduction of CO 2 into the atmosphere due to human activities. However, the ocean
has the capacity to absorb a large quantity of carbon from the atmosphere in the
form of organic material, which can be stored away from the atmosphere in
sediment for long geological periods. However, in subaerial regions the various
forms of carbon compounds will stay in contact with the atmosphere and might
influence climate change.
Formation of Continents
The Earth is in constant motion and has continued to change since its creation 4.7
billion years ago. Some of this evolution is witnessed during a human’s lifetime,
such as when volcanic eruptions, earthquakes or tsunamis disrupt daily activities
or create major catastrophes.
It is difficult to draw the shape of early-formed continents. When the molten
Earth solidified, solid crust started to form isolated pieces of landmass called
‘‘cratons’’. The cratons are thick portions of today’s continent formed from older
pieces of continents. The oldest rock formations or cratons exposed on the surface
of the Earth are Archean in age (3.8–4.4 billion years and older) (Myers and
Crowley 2000). Archean (2,500 million years ago) rocks have been seen in
Greenland, on the Canadian Shield, in Western Australia, and in South Africa.
These first continental-size land mass are also called ‘‘Ur’’ (Hazen 2012). At the
beginning of Earth’s creation, there were no solid landmasses until late in the
Archean period, when small ‘‘proto-continents’’ were formed. These proto-continents probably formed as ‘‘patchy hotspots’’ during the cooling and differentiation
of the ‘‘magma ocean’’ giving rise to mafic and felsic rocks.
The world’s oceans have probably existed from the beginning of our planet’s
history. Evidence suggesting the presence of ancient oceans has been gathered from
the discovery of metamorphosed sedimentary rocks from Canada and Australia
(Wilde et al. 2001). Sediments containing fossils are deposited on the sea floor and
36
2 Our Haven, Planet Earth