The Earth SystemConnections among the great spheres

Our Home Planet

A closed system !

Has well-defined continents

and ocean basins

Only planet presently

known to support life

About 4.5 billion years old

Very dynamic, both

internally and

externally

Earth As A Closed System

Closed system: exchange of energy but negligible

exchange of mass with surroundings

Mass conserved

within system

(no gain or loss)

Four Spheres Within Closed System

Within this closed system are

four major, interlinked

components:

Geosphere

Hydrosphere

Atmosphere

Biosphere

Energy and matter are

exchanged between these

components.

In this course, our focus will be

on the biosphere.

So while we’re thinking about

it…

…Why can Earth sustain life ?

• Not too close or far from Sun, thus preventing life from

freezing or frying

• Large enough to hold atmosphere

• Abundance of water

• Temperature range to allow water to exist in liquid (very

important) as well as gaseous, and solid forms.

• The interaction of the four components or “spheres” of the

Earth system.

The origin of life is a separate issue, which we will discuss

later.

Earth’s Four Spheres

Geosphere

Geosphere: The solid, inorganic Earth, including Earth’s

surface and layers of its interior.

The Earth is

composed of

nested shells

that are

classified

according to

their chemical

and mechanical

characteristics.

crust

mantle

core

lithosphereasthenosphere

mesosphere

outer core

inner core

Composition Mechanical Characteristics

liquid

solid

solid

brittle solidsolid (but

nearly

liquid)

Earth’s Layers: Composition and Mechanical Characteristics

Primarily iron

and nickel

Primarily

silica plus

iron and

magnesium

Primarily silica

plus light

metallic

elements

Note: Lithosphere contains both crust and uppermost (brittle) layer of mantle

Geosphere: Chemical and Mechanical

Characteristics Combined

Some important roles of the geosphere:

1. Contributor of particulate matter (e.g. volcanic ash) to

atmosphere.

2. Ultimate contributor of salts to the ocean (due to ions

being released from weathered rock).

3. Ultimate source of nutrients for all living things.

4. Important contributor of atmospheric gases (from

volcanoes)

5. Movement of plates produces barriers that aid in the

isolation of population of organisms (and therefore

influences evolution).

The Dynamic Geosphere

Processes that occur beneath Earth’s surface are manifest

in earthquakes and volcanism.

These phenomena are linked to the movement of tectonic

plates that, in turn, is driven by internal Earth processes.

Earthquakes Plate BoundariesVolcanoes

97 percent of the earth's water is in

the oceans.

The remaining 3 percent is fresh

water (mostly in ice sheets, but also

in the air as vapour, and below

Earth’s surface as groundwater).

The presence of liquid surface water

makes our planet unique.

Surface temperatures of

oceans

(blue= coldest red=

warmest)

Hydrosphere:The hydrosphere is composed of all of the

water in the Earth system, including water in the

oceans, rivers, lakes, air, and below Earth’s surface.

Hydrosphere

Hydrosphere

Some important roles of the hydrosphere:

1. Moderates climate

2. Transfers heat

3. Organisms need water to transport nutrients and

waste

4. Water is essential in many of Earth’s processes,

from mineral formation to the weathering and

erosion of rock.

Most of our atmosphere is located

close to the earth's surface where it is

most dense.

The air of our planet is 79% nitrogen

and just under 21% oxygen; the small

amount remaining is composed of

carbon dioxide and other gases.

Atmosphere: The atmosphere is the body of gases that

surrounds our planet.

Atmosphere

Also has a layered structure (but we won’t get into this

right now)

Some important roles of the atmosphere:

1. Contains the gases that living things need for

survival (e.g., carbon dioxide for photosynthesis,

and oxygen for aerobic respiration).

2. Transfers heat.

3. Ozone in stratosphere protects living things from

excess ultraviolet radiation.

4. Plays a part in weathering and erosion.

Biosphere

Most of Earth’s life is found from

about 3 metres below the ground

to 30 meters above it and in the

top 200 metres of the oceans and

seas.

Biosphere: The sphere that includes all living organisms.

Plants, animals, and microbes are all part of the

biosphere. It also includes organic matter not yet

decomposed.

But…life can thrive in the most unlikely places, from hot

springs to ice caps.

Some important roles of the biosphere:

1. Aids in weathering (e.g. formation of acids in

soil).

2. An important sink for certain elements

(especially carbon).

3. Mediates the formation of some minerals.

4. Photosynthesis maintains the oxygen content of

the atmosphere.

A Recent Addition to Biosphere: Human Activity

The presence of humans

and the extent of human

influence can be

appreciated by looking at

satellite photos.

Even at night, evidence

of human activity can be

seen.

White dots: major centres of human population

Yellow patches: fires from slash-and-burn farming

Red patches: natural gas burning in major oil fields

Interconnectedness of Spheres

To appreciate how strongly interconnected the Earth’s

spheres really are, we need only to think about what

happens to substances within the system.

For example, the carbon cycle.

Note that at any

given point in

time, carbon

occurs in all of

the great

spheres.

Other Circumstances: Earth’s Spin and Tilt

Earth is not just a static lump of rock !

As it spins on its tilted axis, it different areas of

Earth are exposed to different amounts/intensities of

the Sun’s energy.

This gives us seasons.

Considering Interactions Between the Spheres

Identify some interactions that are represented in this picture

Example 1

Example 2

What about this picture ?

Example 3

…or this one ?

Small-scale example: A forest fire

Interactions Between Spheres: Cause and Effect

Initial Conditions

Geosphere: The ground could have been very

permeable, preventing moisture from being retained in

the upper part of the soil profile.

Hydrosphere: The area could have been prone to fire

due to lack of precipitation.

Atmosphere: The fire could have started due to a

lightning strike.

Biosphere: Dead wood, leaves and needles may have

enhanced the ability of the fire to start and spread.

Relevance to Geosphere

1. Heat from the fire causes rocks to crack (therefore

enhancing weathering).

2. Soil erosion is also enhanced by the removal of

vegetation.

3. Ash particles from the fire alter the chemistry of the

soil.

Relevance to Atmosphere

1. Smoke and ash particles are carried by wind to other areas.

2. Increased precipitation elsewhere is enhanced due to the

ash particles acting as nucleation centres for water droplets.

3. Gaseous pollutants such as carbon dioxide (CO2) are

produced during the burning of the vegetation and carried

into the air by the wind.

Relevance to Hydrosphere

• Heat from the fire further removes moisture from the

air, soil, and vegetation through the process of

evaporation.

• Increased siltation of streams due to enhanced

erosion (particles are then deposited as sediment).

Relevance to Biosphere

1. Immediate destruction of habitat in burn area.

2. Smoke in the air may have coats the lungs of animals,

including people, and affects their ability to breathe.

3. Ash particles in water clogs the gills of fish and other

aquatic organisms.

4. On the positive side, nutrients released from ash from

the fire can, on the long term, benefit future plant

communities.

5. Also, seeds of some plants may require that their outer

shells be burned before they can germinate (so the

forest fire benefits these plants).

Relevance to Biosphere

These types of interactions not only apply to local

scenarios, but also influence changes on global

scale.

Examples of events that may have something to do with

interactions between components of the Earth

system:

1. Initiation of ice ages

2. Mass extinctions

3. Global climate change

4. El Nino events.

We will look at some of these things in detail as the

course progresses.

Global Effects

The Earth’s Atmosphere

The Earth and its Atmosphere

This chapter discusses:

1. Gases in Earth's atmosphere

2. Vertical structure of atmospheric pressure

& temperature

3. Types of weather & climate in the

atmosphere

Solar Energy as Radiation

Figure 1.1

Nearly 150 million kilometers separate the sun and earth, yet solar

radiation drives earth's weather.

Earth's Atmosphere

99% of atmospheric gases, including water vapor, extend only 30

kilometer (km) above earth's surface.

Most of our weather, however, occurs within the first 10 to 15 km.

Figure 1.2

Thin Gaseous envelope

Composition of Atmosphere

• Nitrogen - 78%

• Oxygen - 21%

• Water Vapor – 0 to 4%

• Carbon Dioxide - .037%

• Other gases make up the rest

Atmospheric Gases

Nitrogen, oxygen,

argon, water vapor,

carbon dioxide, and

most other gases

are invisible.

Clouds are not gas,

but condensed

vapor in the form of

liquid droplets.

Ground based

smog, which is

visible, contains

reactants of

nitrogen and ozone.

Ozone – is the primary ingredient of smog!

Variable & Increasing Gases

Figure 1.3

Nitrogen and oxygen concentrations experience little change,

but carbon dioxide, methane, nitrous oxides, and

chlorofluorocarbons are greenhouse gases experiencing

discernable increases in concentration. CO2 has risen more

than 18% since 1958. Fossil fuels are the biggest problem!

Atmospheric Greenhouse Effect

• The warming of the atmosphere by its

absorbing and emitting infrared

radiation while allowing shortwave

radiation to pass through. The gases

mainly responsible for the earth’s

atmospheric greenhouse effect are water

vapor and carbon dioxide.

Aerosols & Pollutants

Human and

natural activities

displace tiny soil,

salt, and ash

particles as

suspended

aerosols,

as well as sulfur

and nitrogen

oxides, and

hydrocarbons as

pollutants.Figure 1.6

Pressure & DensityGravity pulls gases

toward earth's

surface, and the

whole column of

gases weighs 14.7

psi at sea level, a

pressure of 1013.25

mb or 29.92 in.Hg.

The amount of force

exerted Over an area of

surface is called

Air pressure!

Air Density is

The number of air

Molecules in a given

Space (volume)

Vertical Pressure Profile

Atmospheric pressure

decreases rapidly with

height. Climbing to an

altitude of only 5.5 km

where the pressure is

500 mb, would put you

above one-half of the

atmosphere’s

molecules.

Lapse Rate

• The rate at which air temperature

decreases with height.

• The standard (average) lapse rate in the

lower atmosphere is about 6.5°C per 1

km or 3.6°F per 1000 ft.

Temperature Inversion

• An increase in air temperature with

height often called simply an inversion.

• Radiosonde – an instrument that

measures the vertical profile of air

temperature in the atmosphere

(sometimes exceeding 100,000 ft)

Atmospheric Layers

8 layers are defined by constant

trends in average air

temperature (which changes

with pressure and

radiation), where the outer

exosphere is not shown.

1. Troposphere

2. Tropopause

3. Stratosphere

4. Stratopause

5. Mesosphere

6. Mesopause

7. Thermosphere

8. Exosphere

Atmospheric Layers

Figure 1.7

Troposphere – Temp decrease w/ height

Most of our weather occurs in this layer

Varies in height around the globe, but

Averages about 11 km in height.

Tropopause separates Troposphere from

Stratosphere. Generally higher in summer

Lower in winter.

The troposphere is the lowest major atmospheric layer, and is located from the Earth's surface up to the bottom of the stratosphere. It has decreasing temperature with height (at an average rate of 3.5° F per thousand feet (6.5 ° C per kilometer); whereas the stratosphere has either constant or slowly increasing temperature with height. The troposphere is where all of Earth's weather occurs. The boundary that divides the troposphere from the stratosphere is called the "tropopause", located at an altitude of around 5 miles in the winter, to around 8 miles high in the summer, and as high as 11 or 12 miles in the deep tropics. When you see the top of a thunderstorm flatten out into an anvil cloud, like in the illustration above, it is usually because the updrafts in the storm are "bumping up against" the bottom of the stratosphere

Atmospheric Layers

Figure 1.7

Stratosphere

Temperature inversion in stratosphere

Ozone plays a major part in heating the air

At this altitude

Atmospheric Layers

Figure 1.7

Mesosphere

Middle atmosphere – Air thin, pressure low,

Need oxygen to live in this region. Air

quite Cold -90°C (-130°F) near the top of

mesosphere

Atmospheric Layers

Figure 1.7

Thermosphere

“Hot layer” – oxygen molecules absorb

energy from solar Rays warming the air.

Very few atoms and molecules in this

Region.

The Stratosphere and Ozone Layer

Above the troposphere is the stratosphere, where air flow is mostly horizontal. The thin ozone layer in the upper

stratosphere has a high concentration of ozone, a particularly reactive form of oxygen. This layer is primarily responsible

for absorbing the ultraviolet radiation from the Sun. The formation of this layer is a delicate matter, since only when

oxygen is produced in the atmosphere can an ozone layer form and prevent an intense flux of ultraviolet radiation from

reaching the surface, where it is quite hazardous to the evolution of life. There is considerable recent concern that

manmade flourocarbon compounds may be depleting the ozone layer, with dire future consequences for life on the Earth.

The Mesosphere and Ionosphere

Above the stratosphere is the mesosphere and above that is the ionosphere (or thermosphere), where many atoms are

ionized (have gained or lost electrons so they have a net electrical charge). The ionosphere is very thin, but it is where

aurora take place, and is also responsible for absorbing the most energetic photons from the Sun, and for reflecting radio

waves, thereby making long-distance radio communication possible.

Atmospheric Mixture & Charge

Additional layers

include:

a) the homosphere

with 78% nitrogen

and 21% oxygen

b) the poorly

mixed

heterosphere

c) the electrically

charged

ionosphere

Radio Wave Propagation

Figure 1.9 (Ionosphere Radio Prop)

AM radio waves are long enough to interfere with ions in the sun-

charged D layer, but at night the D layer is weak and the AM signal

propagates further, requiring stations to use less power.

Weather & Climate

Weather is comprised of the

elements of:

a) air temperature

b) air pressure

c) humidity

d) clouds

e) precipitation

f) visibility

g) wind

Climate represents long-term

(e.g. 30 yr) averages of weather.

Satellite Instruments

Meteorologists may

study larger weather

patterns with space

borne instruments,

while ground-based

tools often measure a

single point. (GOES

SAT)

Figure 1.10

Meridians

Longitude

Latitude

Middle Latitudes – 30-50N

Middle-latitude cyclonic storm

Hurricane

Thunderstorm

Tornado – most violent disturbance in atms

Surface Weather Map

Figure 1.11

Meteorologists

generate diagrams

of observed

weather from

ground-based

instruments.

This surface map

overlaps in time

with the previous

satellite image.

Low

High

Fronts

Wind Direction

History of Meteorology

• Meteorology is the study of the atmosphere and its

phenomena

• Aristotle wrote a book on natural philosophy (340 BC)

entitled “Meteorologica”

– Sum knowledge of weather/climate at time

– Meteors were all things that fell from the sky or

were seen in the air

– “meteoros” : Greek word meaning “high in air”

Impacts of Weather 1/5

Figure 1.12

Impacts of Weather 2/5

Figure 1.13

Impacts of Weather 3/5

Figure 1.14

Impacts of Weather 4/5

Figure 1.15146 people die each year

In US from flash floods

Impacts of Weather 5/5

Figure 1.16

Lightning strikes earth

100 times every second