THE EARTH’S LIFE SUPPORT
SYSTEMS
• The biosphere
consists of several
physical layers that
contain:
– Air
– Water
– Soil
– Minerals
– Life
Figure 3-6
Biosphere
• Atmosphere
– Membrane of air around the planet.
• Stratosphere
– Lower portion contains ozone to filter out most
of the sun’s harmful UV radiation.
• Hydrosphere
– All the earth’s water: liquid, ice, water vapor
• Lithosphere
– The earth’s crust and upper mantle.
GEOLOGIC PROCESSES
• The earth is made up of a core, mantle, and
crust and is constantly changing as a result
of processes taking place on and below its
surface.
• The earth’s interior consists of:
– Core: innermost zone with solid inner core and
molten outer core that is extremely hot.
– Mantle: solid rock, under which is the
asthenosphere that is melted pliable rock.
– Crust: Outermost zone which underlies the
continents.
Earth
•
•
•
•
orbit: 149,600,000 km (1.00 AU) from Sun
diameter: 12,756.3 km
mass: 5.972e24 kg
Earth’s layers (depths in km)
– 0- 40 Crust
– 40- 2890 Mantle
– 2890-5150 Outer core
– 5150-6378 Inner core
Earth
• Earth’s mass (measured in 10^24 kg)
– atmosphere = 0.0000051
– oceans = 0.0014
– crust = 0.026
– mantle = 4.043
– outer core = 1.835
– inner core = 0.09675
Earth’s Interior
•
•
•
•
Core is made up mostly of iron/nickel
Temperatures in core reach 7500 K
The crust is primarily quartz.
Taken as a whole, the Earth's chemical
composition (by mass) is:
– 34.6% Iron
– 29.5% Oxygen
– 15.2% Silicon
– 12.7% Magnesium
2.4% Nickel
1.9% Sulfur
0.05% Titanium
GEOLOGIC PROCESSES
• Major features of the earth’s crust and
upper mantle.
Figure 15-2
Volcanoes
Abyssal hills
Oceanic crust
(lithosphere)
Abyssal Oceanic
floor
ridge
Abyssal
floor
Trench
Folded
mountain
belt
Abyssal plain
Craton
Continental
shelf
Continental
slope
Continental
rise
Continental crust (lithosphere)
Mantle (lithosphere)
Fig. 15-2, p. 336
Spreading
center
Collision between
two continents
Subduction
zone
Continental
crust
Oceanic
crust
Ocean
trench
Oceanic
crust
Continental
crust
Material cools Cold dense
as it reaches material falls
the outer back through
mantle
mantle
Hot
Mantle
material
convection
rising
cell
through
the
mantle
Two plates move
towards each other.
One is subducted
back into the mantle
on a falling convection
current.
Mantle
Hot outer
core Inner
core
Fig. 15-3, p. 337
INTERNAL GEOLOGIC
PROCESSES
• Huge volumes of heated and molten rack
moving around the earth’s interior form
massive solid plates that move extremely
slowly across the earth’s surface.
– Tectonic plates: huge rigid plates that are
moved with convection cells or currents by
floating on magma or molten rock.
The Earth’s Major Tectonic
Plates
Figure 15-4
Major Plates
•
•
•
•
•
•
•
•
North American Plate
South American Plate
Antarctic Plate
Eurasian Plate
African Plate
Indian-Australian Plate
Nazca Plate
Pacific Plate
Plate Movement
• The extremely slow movements of these
plates cause them to grind into one
another at convergent plate boundaries,
move apart at divergent plate boundaries
and slide past at transform plate
Figure 15-4
boundaries.
Fig. 15-4, p. 338
JUAN DE
FUCA PLATE
EURASIAN PLATE
NORTH
AMERICAN
PLATE
ANATOLIAN
PLATE
CARIBBEAN
PLATE
ARABIAN
AFRICAN PLATE
PLATE
PACIFIC
PLATE
SOUTH
AMERICAN
NAZCA PLATE
PLATE
SOMALIAN
SUBPLATE
CHINA
SUBPLATE
PHILIPPINE
PLATE
INDIAAUSTRALIAN
PLATE
ANTARCTIC PLATE
Divergent plate
boundaries
Convergent plate
boundaries
Transform
faults
Fig. 15-4a, p. 338
Trench
Volcanic island arc
Craton
Transform
fault
Lithosphere
Asthenosphere
Divergent plate boundaries
Lithosphere
Rising
magma
Asthenosphere
Convergent plate boundaries
Lithosphere
Asthenosphere
Transform faults
Fig. 15-4b, p. 338
Animation: Plate Margins
PLAY
ANIMATION
Convergent Plate Boundary
•
•
•
•
Two plates pushed together
Oceanic + Continental = Subduction Zone
Oceanic + Oceanic = Trench
Continental + Continental = Mountain
Range
Divergent Plate Boundary
• Plates moves apart from one another
• Oceanic plates form oceanic ridges
Transform Faults
• Plates slide and grind past one another
along a fracture in the lithosphere
Recylcing Earth’s Crust
• Natural disasters like earthquakes and
volcanoes occur at plate boundaries
• From geologic perspective, however, there
are advantages to plate movement
– Forms mineral deposits and promotes and
sustains life
– Led to the evolution of life on Earth
– Formed Earth’s primitive atmosphere and
therefore climate
– Rich soils
Geologic Time Scale
• ~4.6 billion years ago: Earth believed to
have formed, hot ball of rock
• 3.9 billion years ago: rainstorms
• 3.5 billion years ago: oceans, first living
organisms
Geologic Eras
• Precambrian Era: 4.6 billion years ago- 545 million years
ago
– 87% of Earth’s history
– Prokaryotes dominated
– First eukaryotes appeared ~ 1.5 billion years ago
– Simple multicellular organisms in seas
• Paleozoic Era: 545 million years ago – 248 million years
ago
– “Explosion of life”
– Many types of invertebrates in shallow seas
– Early: earliest vertebrates
– Middle: amphibians
– Later: reptiles
Geologic Eras
• Mesozoic Era: 248 million years ago – 65 million years
ago
– Triassic: mammals made first appearance
– Jurassic: “age of dinosaurs”
– Cretaceous: radiation of mammals and evolution of
flowering plants
– Plate Tectonics: continental shift
• Cenozoic Era: 65 million years ago – now
– Mammals flourish
– Primates evolve
– Extinctions affect diversity
– Modern human species evolved ~200,000 years ago
EXTERNAL GEOLOGIC
PROCESSES
• Surface processes
– Based largely on energy from the sun and
gravity
• Tends to wear down Earth’s surface and
produce a variety of landforms by the
buildup of eroded sediment
• Erosion
• Weathering
Wearing Down and Building Up
the Earth’s Surface
• Weathering
is an
external
process that
wears the
earth’s
surface
down.
Figure 15-6
EROSION
• Process by which material is dissolved,
loosened or worn away from one part of
the earth’s surface and deposited in other
places
• Streams are most important agents of
erosion
MINERALS, ROCKS, AND THE
ROCK CYCLE
• The earth’s crust consists of solid
inorganic elements and compounds
called minerals that can sometimes be
used as resources.
– Mineral resource: is a concentration of
naturally occurring material in or on the
earth’s crust that can be extracted and
processed into useful materials at an
affordable cost.
ROCK
• A very slow chemical cycle recycles three types
of rock found in the earth’s crust:
– Sedimentary rock (sandstone, limestone). Formed
from sediment of pre-existing rocks that are
weathered and eroded
– Metamorphic rock (slate, marble, quartzite). Formed
when pre-existing rock is subjected to high
temperatures or pressure
– Igneous rock (granite, pumice, basalt). Formed from
cooled magma at or below earth’s surface
Erosion
Transportation
Weathering
Deposition
Igneous rock
Granite,
pumice,
basalt
Sedimentary
rock
Sandstone,
limestone
Heat, pressure
Cooling
Heat, pressure,
stress
Magma
(molten rock)
Melting
Metamorphic rock
Slate, marble,
gneiss, quartzite
Fig. 15-8, p. 343
SOIL: A RENEWABLE
RESOURCE
• Soil is a slowly renewed resource that
provides most of the nutrients needed for
plant growth and also helps purify water.
– Soil formation begins when bedrock is broken
down by physical, chemical and biological
processes called weathering.
• Mature soils, or soils that have developed
over a long time are arranged in a series of
horizontal layers called soil horizons.
COMPONENTS OF SOIL
Soil Formation:
•Product of weathering
•Function of parent
material, climate,
topography, organisms, and
time
Oak tree
Wood
sorrel
Lords and
ladies
Fern
O horizon
Leaf litter
Dog violet
Grasses and
small shrubs
Earthworm
Millipede
Honey
fungus
Mole
Organic debris
builds up
Rock
fragments
Moss and
lichen
A horizon
Topsoil
B horizon
Subsoil
Bedrock
Immature soil
Regolith
Young soil
Pseudoscorpion
C horizon
Mite
Parent
material
Nematode
Root system
Mature soil
Red Earth
Mite
Springtail
Actinomycetes
Fungus
Bacteria
Fig. 3-23, p. 68
Animation: Soil Profile
PLAY
ANIMATION
Layers in Mature Soils
• Infiltration: the downward movement of
water through soil.
• Leaching: dissolving of minerals and
organic matter in upper layers carrying
them to lower layers.
• The soil type determines the degree of
infiltration and leaching.
Soil Profiles of the
Principal
Terrestrial Soil
Types
Figure 3-24
Mosaic of
closely
packed
pebbles,
boulders
Weak humusmineral mixture
Desert Soil
(hot, dry climate)
Dry, brown to
reddish-brown
with variable
accumulations
of clay, calcium
and carbonate,
and soluble
salts
Alkaline,
dark,
and rich
in humus
Clay,
calcium
compounds
Grassland Soil
semiarid climate)
Fig. 3-24a, p. 69
Acidic
light-colored
humus
Iron and
aluminum
compounds
mixed with
clay
Tropical Rain Forest Soil
(humid, tropical climate)
Fig. 3-24b, p. 69
Forest litter leaf
mold
Humus-mineral
mixture
Light, grayishbrown, silt loam
Dark brown
firm clay
Deciduous Forest Soil
(humid, mild climate)
Fig. 3-24b, p. 69
Acid litter
and humus
Light-colored
and acidic
Humus and
iron and
aluminum
compounds
Coniferous Forest Soil
(humid, cold climate)
Fig. 3-24b, p. 69
Soil Properties
• Soils vary in the size
of the particles they
contain, the amount
of space between
these particles, and
how rapidly water
flows through them.
Figure 3-25
Atmosphere
• Thin layer of gases that surrounds the Earth
• Composed of:
–
–
–
–
–
–
–
–
Nitrogen
Oxygen
Water vapor
Argon
Carbon dioxide
Neon
Helium
Other
Atmosphere has
changed
• Early Earth’s atmosphere
consisted only of methane, water
vapor, ammonia and hydrogen
• Photosynthesis greatly changed
our atmosphere!
Five Layers
Troposphere
• Earth’s surface to ~ 6 miles
above the surface
• Contains ~ 90% of
atmospheric gases
• Where weather occurs
Stratosphere
• 6 miles to about 30 miles
above Earth’s surface
• Air is less dense
• Less turbulent air flow
• Contains the ozone layer
Mesosphere,
Thermosphere,
Exosphere
• Gases become thinner and
thinner
• Colder and colder
• Exosphere merges with outer
space