Environment and Environmental changes.
• Environment= climate and environmental changes= global
• the environment covers all of the ambient influences in the
physical, biological, and human world
• physical world involves the atmosphere lithosphere
• the biosphere is contained by these element of physical
environment and there interaction
Our atmosphere is composed mostly of N (78%) and O (20%).
It produces a modest greenhouse effect because of small, but
significant concentrations of CO2, CH4 and other gasses
• Our hydrosphere is unique in our solar system. Water can
exist in gaseous, liquid and solid forms and readily exchanges
between the three states. Energy exchanges accompany
changes in state.
• Our lithosphere is very dynamic with a hot differentiated
interior that drives plate tectonics.
• Our biosphere is comprised of the plants and animals that we
see, but also contains huge numbers of microbes, the most
successful and persistent of Earth’s biota. These are essential
to biogeochemical cycles (e.g. the N cycle) and directly and
indirectly influence climate.
• That there have been large and essentially continuous
environmental changes throughout geologic time.
• That those changes have been natural, and until very recently
been without human influence.
• That hominids/hominins evolve some 4 million years ago, but
appear to have had little to modest environmental impact until
the Holocene, the last 10,500 years.
• Throughout most of geologic time the Earth was much warmer
than it is today – it had a much larger greenhouse effect. Its geography has changed constantly.
• The biomes that we are familiar with – the boreal forest, prairie
grasslands, tundra, etc. are recent phenomena.
• The ‘normal’ warm world is mostly tropical/subtropical. Forests
extended into polar regions
What drives the earth systems?
• Two major controls both involve energy
• The first is generated in the earths interior this determines the
place and time for an earthquake or volcano and controls
critical chemical cycles, notably the carbon cycle. The
package is called plate tectonics.
•other source of energy is external- solar radiation it has
changed through time and moves at a range of temporal scales
therefore the solar energy impacts the Earth's system not only
by determine the amount emitted but how that energy being
processed by the atmosphere and the Earth's system- Here we
see energy one and energy two interacting together
• How does it impact the earth system ? It is not only determined
by the two systems ( e.g volcanoes and the climate relationship
between the two and the effects it had on the climate
Systems and there behaviours
• The earth's environment can often be considered a large
system- the consequence of the interactions between huge
number of subsystems
• all systems input process and output system ( input energy into
the earth and them output energy )
• Open (output) systems exchange both energy and matter,
while closed systems are open for energy, but closed for
• another subsystem is a closed system hydrologic it holds
energy •For Example: the Earth’s energy budget is open. It has
inputs (mostly solar) and outputs. The hydrosphere, a
subsystem, is essentially closed. It’s driven by energy (open),
but the amount of water in the Earth system is finite (closed).
Small subsystems – a lake, a forest, a field,etc. are open.
Feedback and Equilibrium
• The behaviour of systems is determined by feedback.
In many natural systems, the interaction of physical and biological
variables tends to keep the system in some general balance or
equilibrium. These dampening effects are called negative
feedback because if one component changes it may add a
e.g. energy input to the Earth system is uneven. There’s a surplus in
the Tropics and a deficit in high latitudes. The oceanic and
atmospheric circulations act as negative feedback to transfer
energy from areas of surplus to areas of deficit.
Changes in one or more components in the system may produce
positive feedback and induce changes in the behaviour of that
e.g. global warming is generally attributed to changes in the
proportion of greenhouse gasses – a consequence of fossil fuel
burning, deforestation, etc.
• In time there may often be a steady state equilibrium --> theres
no major disruption that goes on here however there may show
a trend which is called dynamic equilibrium
•In part, the ability of a system to maintain equilibrium depends
on its resilience. In general, complex systems are more
resilient than simple ones (natural vs. anthropogenic
systems). Lecture #2:
• there are two major things that drive the earth one is solar
energy the other is plate tectonics
• In readings 2 and 3 you will see that the segment has a general
treatment of plate tectonics and secondly consider volcanic
activity and its real and potential impacts on society
• Plate tectonics were called continental however it is much more
than rafting continents it involves the creation and recycling of
the earth;s crust and associated with tectonics and volcanic
• This has been going on as long as the Earth's has had a crust
about 4 billion years
• The latest ‘cycle’ began with the breakup of a supercontinent
called Pangaea about 250 MYBP.
It is a continuous process with no real beginning or end.
Why is the Crust so mobile?
• the reason the crust is so mobile is because the serious of
large currents in Mantel ( the Mantel Structure diagram ) it is
kept moulded in the inner solar energy
• The Core of the North American plate is the Canadian Shield in
Africa, South America are mostly shielded it is in these areas
that we find the oldest rocks
• As you go away from the centre of the earth the rocks gets old
and the spreading process begins
• we can measure then through satellite navigate which son
which shows us the pattern of the seafloor spreading ( this is
the plate tectonics spreading )
• Therefore as this is occurring the oceans crust is being
• In the past of Geography continents were not tog together the
occurrence of Pangea made them closer
Plate Tectonics and Volcanism • they appear in separate places usually in subduction zones
Mountains and Plate Tectonics
• related to plate movements and continents drifting due to
Pangea drifting example: Hamilayes
• therefore with this occurring more mountains forming
Earthquake's and Volcanism Activity
• Islands are being created in the hot spots the Haiiwan hotspot
Impact of Plate Tectonics and Earth Environment
• changes global geography by the agglomeration and dispersal
of continental masses
• As soon as you block something It changes global topography
mostly by mountain building.
It exerts a major control on global climate on a range of time scales. It
controls the global carbon cycle hence the size of the Earth’s
• it does this through a) changing the locations of continents ,
changing their mass and topography and influencing
• Continental location and topography determine the patterns of
• They also exert a major control on oceanic circulation.
• connected in the changes of water it is chopped up due to
Plate Tectonics influences Atmospheric chemistry and
• this is connected to volcanic activity
• overall it will affect the world's air ( dust will get in the way)
• Plate tectonics also influences climate through atmospheric
chemistry and atmospheric transparency.
• Most of this is connected to volcanic activity (to the effects
of individual eruptions, and to