Spheres of the Earth
Atmosphere
Biosphere
Hydrosphere
Lithosphere
Anthrosphere
Atmosphere
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The Earth is surrounded by a blanket of air, which we call the atmosphere. It
reaches over 560 kilometers (348 miles) from the surface of the Earth, so we
are only able to see what occurs fairly close to the ground. Early attempts at
studying the nature of the atmosphere used clues from the weather, the
beautiful multi-colored sunsets and sunrises, and the twinkling of stars. With
the use of sensitive instruments from space, we are able to get a better view
of the functioning of our atmosphere.
Life on Earth is supported by the atmosphere, solar energy, and our planet's
magnetic fields. The atmosphere absorbs the energy from the Sun, recycles
water and other chemicals, and works with the electrical and magnetic forces
to provide a moderate climate. The atmosphere also protects us from highenergy radiation and the frigid vacuum of space.
The envelope of gas surrounding the Earth changes from the ground up.
Four distinct layers have been identified using thermal characteristics
(temperature changes), chemical composition, movement, and density.
Layers of the Atmosphere
• Thermosphere—highest
• Mesosphere
• Stratosphere (contains ozone)
• Troposphere---layer we live in
Earth as a system
• Can you think of any other spheres that interact
with the atmosphere?
• Biosphere?
• Hydrosphere?
• Lithosphere?
Biosphere
• The term "Biosphere" was coined by Russian scientist Vladimir
Vernadsky in the 1929. The biosphere is the life zone of the Earth
and includes all living organisms, including man, and all organic
matter that has not yet decomposed. Life evolved on earth during its
early history between 4.5 and 3.8 billion years ago and the biosphere
readily distinguishes our planet from all others in the solar system.
The chemical reactions of life (e.g., photosynthesis-respiration,
carbonate precipitation, etc.) have also imparted a strong signal on
the chemical composition of the atmosphere, transforming the
atmosphere from reducing conditions to and oxidizing environment
with free oxygen. The biosphere is structured into a hierarchy known
as the food chain whereby all life is dependent upon the first tier (i.e.
mainly the primary producers that are capable of photosynthesis).
Energy and mass is transferred from one level of the food chain to
the next with an efficiency of about 10%. All organisms are
intrinsically linked to their physical environment and the relationship
between an organism and its environment is the study of ecology.
The biosphere can be divided into distinct ecosystems that represent
the interactions between a group of organisms forming a trophic
pyramid and the environment or habitat in which they live.
Biotic vs. Abiotic
• Bio = means life
• Biotic—living parts or components
• Abiotic—nonliving parts of components (air, water,
temperature)
Earth as a System
• Can you think of any other spheres that interact
with the biosphere?
• Atmosphere?
• Hydrosphere?
• Lithosphere?
Hydrosphere
• The hydrosphere includes all water on Earth. In one respect,
planet Earth is a misnomer in that 71% of the earth is covered
by water and only 29% is terra firma. Indeed, the abundance of
water on Earth is a unique feature that clearly distinguishes our
"Blue Planet" from others in the solar system. Not a drop of
liquid water can be found anywhere else in the solar system. It
is because the Earth has just the right mass, the right chemical
composition, the right atmosphere, and is the right distance
from the Sun (the "Goldilocks" principle) that permits water to
exist mainly as a liquid. However, the range of surface
temperatures and pressures of our planet permit water to exist
in all three states: solid (ice), liquid (water), and gas (water
vapor). Most of the water is contained in the oceans and the
high heat capacity of this large volume of water (1.35 million
cubic kilometers) buffers the Earth surface from large
temperature changes such as those observed on the moon.
Water is the universal solvent and the basis of all life on our
Planet. It is an essential life-sustaining resource which led
Benjamin Franklin to comment "When the well's dry, we know
the worth of water."
Hydrosphere
Earth as a System
• Can you think of any other spheres that interact
with the biosphere?
• Atmosphere?
• Biosphere?
• Lithosphere?
Lithosphere
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The lithosphere (from the Greek for "rocky" sphere) is the solid outermost
shell of a rocky planet. On the Earth, the lithosphere includes the crust and
the uppermost layer of the mantle (the upper mantle or lower lithosphere)
which is joined to the crust. The lithosphere is broken up into different plates
as shown by the picture.
The distinguishing characteristic of the lithosphere is not composition, but its
flow properties. Under the influence of the low-intensity, long-term stresses
that drive plate tectonic motions, the lithosphere responds essentially as a
rigid shell and thus deforms primarily through brittle failure, while the
asthenosphere accommodates strain through plastic deformation. Both the
crust and upper mantle float on the more plastic asthenosphere. The crust is
distinguished from the mantle, and hence the upper mantle, by the change in
chemical composition that takes place at the Moho discontinuity. The
thickness of the lithosphere varies from around 1.6 km (1 mi) at the midocean ridges to approximately 130 km (80 mi) beneath older continental
crust. The thickness of the continental lithospheric plates is probably around
150 kilometers (93 mi).
As the cooling surface layer of the Earth's convection system, the lithosphere
thickens over time. It is fragmented into relatively strong pieces, called
tectonic plates, which move independently relative to one another. This
movement of lithospheric plates is described as plate tectonics. There are
two types of lithosphere
Lithosphere
Earth as a System
• Can you think of any other spheres that interact
with the biosphere?
• Atmosphere?
• Biosphere?
• Hydrosphere?
Anthrosphere
• Man and his direct ancestors (hominids) have graced the planet for
only about three million years. For almost all of this period the human
population totaled less than 5 to 10 million individuals. Homo sapiens
have increased their numbers exponentially from 1650 to present
rising to the current population of 5.5 billion. If this growth continued
unabated, the human population would reach 8 billion in the year
2000, 14 billion in the year 2010, 60 billion in the year 2020, and
infinity by the year 2023. Of course, unlimited growth in an
environment of finite resources is impossible because growth will
eventually deplete the available resources and the population will
collapse. Indeed one of the kindest things that the human species
could do for planet Earth is to control the rate of growth of the
anthrosphere.
Anthrosphere
• Interactions of Homo sapiens with all aspects of
the environment
• We are going to look at each sphere, the
interactions, and the solutions as well as the
problems created by the human race.