Download Introduction to the Earth

Introduction to the Earth
Basic Terminology and Concepts
Spring 2012 , Lecture 1
Ecosphere
• That part of the earth consisting of the
atmosphere, hydrosphere, lithosphere, and
biosphere
2
Atmosphere
• The gaseous layer which surrounds the earth, and
which is held by gravitational attraction. It
consists of layers, the bottom ones of which are:







Thermosphere > 80 km
Mesopause
Mesosphere
45 - 80 km
Stratopause
Stratosphere 12 - 45 km
Tropopause
Troposphere 0 -12 km
3
Hydrosphere
• Earth's water, in any physical state –
 Gaseous
 Liquid
 Solid
4
Lithosphere
• The outermost part of the solid earth,
consisting of the entire crust and the upper
mantle, from the surface to a depth of about
70 kilometers (km)
• It is stronger and mechanically more rigid
than the asthenosphere (70 - 250 km),
which lies under it
5
Interior of the Earth
• Crust –
 Continental (0-40 km, to a maximum of 100km)
 Oceanic (0-10 km)
• Mantle –
 Upper (bottom of crust to 700 km, and includes the
transition zone (350 to 700 km)
 Lower (700 - 2900 km)
• Core –
 Outer (2900 - 4980 km - liquid iron-nickel)
 Inner (4980 - 6370 km - solid)
6
Biosphere
• Interface layer between earth's crust,
atmosphere, and hydrosphere where life is
found
• Includes the total ecosystem of the earth
7
Ecosystem
• Community of interacting organisms, of all
species
• Includes interactions of this community
with the chemical and physical systems of
earth
8
Human Activities
• Interact with the natural world, causing
changes in the ecosystem
• Changes vary in magnitude and temporal
scale
9
Environmental Issues
• Changes in the ecosphere caused by:
 Natural processes
 Human activities
• Often cause change
• Affect the rate at which change occurs
• Or both
10
Changes By Other Species
• Humans are not the only species to cause
environmental change
• Cyanobacteria, the first organisms capable
of photosynthesis, gradually changed the
atmosphere of earth from one without
oxygen to one with the present 21% oxygen
content
11
So What Makes Humans
Different?
• Humans are the first species to be aware of
their influence
• Humans assume, to some extent,
responsibility for wise management of the
planet
• Humans affect change at rates
unprecedented in the geological record
12
Technology Improvements
• During the last fifty years
• Have greatly contributed to our awareness
of environmental change
 Especially contributing to our knowledge of
global scale processes
• Greatly enhanced out knowledge of the
temporal scale of global change
13
Examples of Technological
Change
• Satellite observations
• Computational power
• Rapid communication (Internet)
14
Changes to the Ecosphere
• Many examples of modification of
ecospheric components have been described
• Representative examples of these
modifications are shown on the following
slides
15
Atmospheric Modifications
• Depletion of ozone (O3) in the ozone layer
(stratosphere) which affects UV light
absorption
 Ozone “hole”
 Leads to increased rates of skin cancer
• Acid deposition – introduction of pollutant
gasses into the atmosphere leads to the
formation of “acid rain”
16
Atmospheric Modifications cont.
• Modification of the climate system by the
introduction of “greenhouse” gases
 Major gases are carbon dioxide, freons,
methane, nitrous oxide
 Are leading to a warmer earth, and will
increase number and severity of major storms
 May affect short and medium term climate, and
may modify the areas in which food can be
grown
 May create climate refugees
17
Hydrological Modifications
• Diagram shows a local
example of the
hydrological cycle
18
Hydrological Cycle
Modifications
•
•
•
•
Withdrawal of water
Pollution of water
Impoundment of water (dams)
Modifications in erosion and depositional rates
 Silting of rivers and estuaries
 Increased erosion below dams
 Changes in form of precipitation – rain rather than
snow
19
Biosphere Modifications
• Mobilization and redistribution of chemical
elements
• Most important carbon (C), nitrogen (N),
and oxygen (O)
 Results in enrichment and depletion of various parts
of the system, leading to problems like red tide,
depletion of soil productivty, etc.
20
Biosphere Modifications cont.
• Human activities change natural environment
 Often results in changes in species distribution,
especially in loss of biological diversity (biodiversity)
 Rapid expansion of urban and suburban areas decreases
available habitat
 Deforestation
 Expansion of farming into marginal environments
 Land use that is insensitive to long term changes
• Salinization
21
Results of Environmental Change
• Species reduction
 Mass mortality - a large number of individuals die,
which may lead to a new equilibrium distribution, with
a smaller number of individuals of the species in
question, or the original equilibrium may be
approximately restored, to precatastrophe levels
 Extinction - A complete elimination of a species.
Extinction can and does occur naturally - Man's
activities have increased the rate of extinction
22
Natural Events
• Natural events often lead to mass mortality in
many species - extinction may occur in severely
geographically restricted species
• Examples:





Earthquakes
Volcanoes
Tsunamis
Hurricanes
Small meteorite impacts
23
Large Scale Extinction
• Large meteorite impacts can result in mass
extinctions
 Example: Cretaceous-Tertiary event that wiped
dinosaurs, and many other species, from the
face of the earth
• Large scale nuclear war would probably
have the same effect
24
Environmental Action
• Awareness of environmental change does
not always translate to actions favorable to
the stabilization of the ecosystem
• Why?
25
Political Problems
• Politicians make most policy decisions, yet
relatively few politicians have any training
in science or technology
 Some overcome this by relying on
science/technology advisors
• Political considerations may cause them to
rely more heavily on political or economic
advisories, whose perspective is usually
focused on a much smaller time scale
26
Economic Gain
• Short term economic gain is a powerful motive
• Example: Drilling for oil in the Arctic Wildlife
Preserve will provide profit, and will very
temporarily stave off the decline in oil production
 This may make the final decrease in petroleum even
more difficult for humans, since we will have built
more automobiles, power plants, etc.
 It will also create immense difficulties for many Arctic
species
27
Sources of Pollution
• Pollution may occur from a variety of
sources
• Generally we can divide pollution sources
into two types:
 Point sources – pollution emanating from a
single source, such as a power plant smokestack
 Non-point sources – pollution derived from a
variety of sources, such as smog from
automobile exhaust
28
Scope of Environmental
Problems
• Environmental problems are generally split
into one of three groups, with the possibility
of overlap between groups
 Local – effluent introduced into a stream from
an industrial plant
 Regional – acid rain in the northeastern U.S.,
extending into Canada
 Global – Greenhouse gas warming of the planet
29