Download The Earth As A System

The Earth As A System
The Earth Is Unique Because It
Is The Only Planet That:
• Has liquid water
• Has an atmosphere with oxygen
• Supports life
One reason that scientists study
the characteristics of earth that
support life is so that they can
investigate other planets that
may support life.
Earth Basics
• The earth is the 3rd planet from the sun.
• The earth formed about 4.6 billion years ago.
• About 71 percent of the earth is covered with
water.
• The spinning earth is an oblate spheroid with a
polar diameter of 40,007 km and a polar
diameter of 40,074 km.
• The earth is relatively smooth when compared to
other planets.
The earth’s interior cannot be studied directly but is
analyzed with the use of seismic waves. Three
compositional zones have been identified:
• The outermost layer of solid rock is the crust. It
makes up less than one percent of the earth. It
varies in thickness from only 5-10 km below the
oceans and up to 15-80 km below the
continents.
• The Mohorovicic Discontinuity or Moho marks
the beginning of the mantle. The mantle is
made up of heavy rock making up 2/3 of the
earth’s mass and is 2900 km thick.
• The core at the center of the earth has a radius
of about 3500 km and is made up mostly of iron
and nickel.
The compositional model of the earth has
been divided into five structural zones:
• Below the crust, the uppermost part of the
mantle is cool and brittle. This earth zone is
called the lithosphere.
• Below the lithosphere in the upper mantle is the
less rigid asthenosphere which is 200-250 km
thick and has the ability to flow like plastic.
• The solid rock below the asthenosphere is called
the mesosphere.
• At a depth of 2,900 km the liquid outer core
begins and extends to 5,150 km where the solid
inner core begins.
The movements in the earth’s
core generate a huge magnetic
field around the earth that
reaches far into space. This
magnetosphere concentrates
into two magnetic poles on the
earth’s surface.
The Earth, like all bodies in the
universe is affected by gravity.
Newton’s Law of Gravitation
gives us the ability to describe
this universal force.
The force of attraction that the
earth exerts on all objects is
called weight. Weight is
determined by the amount of
mass in an object. Weight
varies with an object’s location
on the earth because the earth
is not a perfect sphere.
Energy In The Earth System
Section 2
Earth System Science
An organized group of related
objects, components, or
subsystems that interact to
create a whole is a system.
The function of any system
depends on the organization of
its matter and the flow of its
energy.
A closed earth system is one in which
matter is not exchanged with the
surroundings.
In an open earth system, both
matter and energy may be
exchanged with the
environment.
Technically, all of the systems
that make up the Earth are
open. But the Earth system
itself is closed. Very little matter
is exchanged with space.
The matter on the earth is divided
into 4 spheres.
•
•
•
•
Atmosphere
Hydrosphere
Geosphere
Biosphere
Exchanges of energy on earth
follow two strict laws:
• The First Law of Thermodynamics Energy is neither created nor destroyed
but simply changes forms.
• The Second Law of Thermodynamics Matter becomes less organized over time.
The energy that drives the geology of the
earth comes from 3 sources within the earth
• Radioactive decay
• Gravitational contraction
• Heat left over from the formation of the
earth.
Interacting systems at the
earth’s surface receive their
energy from the sun.
The Earth system contains a
number of biochemical cycles in
which vital energy and matter is
moved between reservoirs over
a period of hours to millions of
years.
Four main biochemical cycles
include the:
•
•
•
•
Nitrogen cycle
Carbon cycle
Phosphorus cycle
Water cycle
Phosphorus enters the soil and
water when rock breaks down.
It is then absorbed by plants
and cycled through animals with
decomposition.
All of the natural cycles can be
affected by human activities.
Ecology
The study of the complex
relationships between living things
and their environment.
The earth’s environment is
studied by dividing it up into
smaller environments called
ecosystems. Each ecosystem
consists of a community of living
things together with a nonliving
environment.
Ecosystems are often studied by
the way that they cycle food:
• Producers – Green plants that make their
own food by using energy from the sun.
• Consumers – Animals that feed on
producers and other consumers.
• Decomposers – Bacteria and fungi that
break down detritus to make nutrients
available to plants again.
Each environment can only
support a given number of
organisms and still cycle matter
and transfer energy efficiently.
This maximum number of
organisms is called the carrying
capacity.
After a disturbance, ecosystems
are able to restore the balance
of nature again over time. If the
physical factors of the
environment are not
permanently changed,
ecosystems can restore
themselves to their original
state.
One should remember that
nutrients are cycled as they
move through the complicated
food web of an ecosystem but
energy is lost to heat as it
passes through the system and
cannot be reused.
It is each person’s responsibility to
be a steward of the environment.
We need fertile soils, clean air, and
water to live in our biosphere.
Overconsumption and pollution
can destroy these balances.
It is a constant task to care for our
environmental home.