3.1.1. WATER AND CARBON CYCLES
3.1.1.1 Water and carbon cycles as natural
systems in physical geography: systems concepts
and their application to the water and carbon
cycles inputs – outputs, energy,
stores/components, flows/transfers,
positive/negative feedback, dynamic equilibrium.
3.1.1.2 The Water cycle
Key terms:
• System = a set of interrelated components working together towards some kind of process.
• Open system = these are where matter and energy can be transferred from the system
across the boundary into the surrounding environment. E.g. most ecosystems.
• Closed system = these have transfers of energy both into and beyond the system boundary
but not transfer of matter. e.g. global hydrological cycle. They don’t exist in their pure form
in nature.
• Isolated system = these have no interactions with anything outside the system boundary.
There is no input or output of energy or matter. Many controlled laboratory experiments are
this type of system and they are rare in nature. On a large scale the entire universe could be
considered an isolated system.
At the global level the Earth has four major subsystems, the atmosphere, lithosphere, hydrosphere
and biosphere (and cryosphere). Each of these can be considered to be an open system that forms
part of a chain; a cascading system.
Why use a systems approach?
• It helps us understand how energy is transferred between the components of a system and
how those components themselves can change.
• It helps us to appreciate how both natural change and human activities can impact upon the
environment.
• It helps to simplify complex systems and see them as a whole picture.
,
, •
3.1.1.1 Water and carbon cycles as natural
systems in physical geography: systems concepts
and their application to the water and carbon
cycles inputs – outputs, energy,
stores/components, flows/transfers,
positive/negative feedback, dynamic equilibrium.
3.1.1.2 The Water cycle
Key terms:
• System = a set of interrelated components working together towards some kind of process.
• Open system = these are where matter and energy can be transferred from the system
across the boundary into the surrounding environment. E.g. most ecosystems.
• Closed system = these have transfers of energy both into and beyond the system boundary
but not transfer of matter. e.g. global hydrological cycle. They don’t exist in their pure form
in nature.
• Isolated system = these have no interactions with anything outside the system boundary.
There is no input or output of energy or matter. Many controlled laboratory experiments are
this type of system and they are rare in nature. On a large scale the entire universe could be
considered an isolated system.
At the global level the Earth has four major subsystems, the atmosphere, lithosphere, hydrosphere
and biosphere (and cryosphere). Each of these can be considered to be an open system that forms
part of a chain; a cascading system.
Why use a systems approach?
• It helps us understand how energy is transferred between the components of a system and
how those components themselves can change.
• It helps us to appreciate how both natural change and human activities can impact upon the
environment.
• It helps to simplify complex systems and see them as a whole picture.
,
, •
