Introduction to the Earth

Basic Terminology and Concepts

Spring 2012 , Lecture 1

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Ecosphere

• That part of the earth consisting of the atmosphere, hydrosphere, lithosphere, and biosphere

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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

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Hydrosphere

• Earth's water, in any physical state – Gaseous Liquid Solid

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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

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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)

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Biosphere

• Interface layer between earth's crust, atmosphere, and hydrosphere where life is found

• Includes the total ecosystem of the earth

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Ecosystem

• Community of interacting organisms, of all species

• Includes interactions of this community with the chemical and physical systems of earth

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Human Activities

• Interact with the natural world, causing changes in the ecosystem

• Changes vary in magnitude and temporal scale

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Environmental Issues

• Changes in the ecosphere caused by: Natural processes Human activities

• Often cause change

• Affect the rate at which change occurs

• Or both

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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

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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

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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

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Examples of Technological Change

• Satellite observations

• Computational power

• Rapid communication (Internet)

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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

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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”

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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

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Hydrological Modifications

• Diagram shows a local example of the hydrological cycle

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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

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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.

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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

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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

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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

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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

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Environmental Action

• Awareness of environmental change does not always translate to actions favorable to the stabilization of the ecosystem

• Why?

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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

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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

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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

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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