Transcript B. The Mantle

Chp10: Earth Interior
Structure of the Modern Earth
I. The Earth consists of three concentric layers:
a. the core
b. the mantle
c. the crust
They are formed as a result of:
-density differences between the layers
-variations in composition
-differences in temperature and pressure
II. The Characteristics of the Core:
a. The Core is thought to be composed of iron with some nickel.
b. It is spherical in shape with its outer surface lying 2900 km below th
outer surface of the earth.
c. The total diameter of the core is 3470 km.
d. It has an average density of about 10 to 13 grams/cm3 and
comprises 16% of the earth’s volume.
Chp 10: Earth’s Interior
Chp10:
Earth
Interior
Characteristics of the Core (continued….)
d. Seismic Tomography data (studying the earth’s interior indirectly
by studying the behavior of earthquake waves) indicate that the core
has a small Solid Inner Region (1220 km in diameter) surrounded
by an apparently Liquid Outer Region (2250 km thick).
III. The Characteristics of the Mantle:
a. The Mantle surrounds the core and comprises about 83%of the earth’s volume.
b. It is less dense than the core with an average density of approximately 3.3 – 5.7
grams/cm3.
c. It is composed largely of Peridotite, a dark, dense, igneous rock containing high
amounts of iron and magnesium.
d. The Mantle can be divided into three regions:
1.The Lower Mantle – This is solid and comprises most of the volume of the
earth’s interior.
2. The Upper Mantle – This consists of the Asthenosphere and the overlying solid
mantle rocks up to the base of the crust.
-The asthenosphere surrounds the lower mantle, has the same peridotite composition
- It behaves plastically and slowly flows. Partial melting within the asthenosphere
generates Magma, molten rock material, some of which rises to the surface
because it is less dense than the material from which it was derived.
Chp 10: Earth’s Interior
Our knowledge of
Earth’s interior
largely comes from
studying wave
propagation from
earthquakes…..the
Relative density of
a rock can be estimated
based upon the travel
time of wave from the
focus to the seismograph
station.
Chp 10: Earth’s Interior
Recall that S waves
cannot pass through
liquids (like outer core)
Chp10: Earth Interior
hree Subdivisions of the Mantle, continued….
. The Lithosphere – This is the solid portion of the upper mantle and the overlying crust.
The lithosphere is broken into numerous pieces called Plates that move over the
asthenosphere as the result of underlying Convection Cells (or Mantle Plumes
generated from heat).
IV. The Characteristics of the Crust:
The Crust is the outermost layer of the earth. It consists of two types of rock materials:
a. Continental Crust – (20 – 90 km thick) this material comprises most of the
continental plates. It has a density of 2.7 grams/cm3, Granite, is rich in silica, aluminu
This type of rock material is referred to as being “Sialic” or “Felsic”.
b. Oceanic Crust – (5 – 10 km thick) has a density of 3.0 grams/cm3 and is largely
comprised of the igneous rock Basalt, which is rich in iron and magnesium.
This type of rock material as referred to as being “Mafic” or “Basaltic”.
V. The Refinement of the Earth’s Crust
a. The early outer crust of the earth was a mixture of sialic and mafic material.
b. The following processes occurred to separate the sialic materials from the mafic.
This allowed continents to differentiate from oceanic material.
Sial=granite
Chp 10: Earth’s
Interior
Mafic=basalt
Chp10: Earth Interior
A. Separation of Mafic Materials from Sialic
1. Partial Melting – This is the process whereby hot mantle plumes rising up from the
upper mantle heats (“partially melts”) the overlying mixture of mafics and sialics.
This causes the denser mafic materials to separate downward, leaving the less dense
sialic materials above….
2. Fractional Crystallization – Mafic materials, being high in iron and magnesium,
will crystallize at a higher temperature than sialic material, that is high in silica and
aluminum. If the entire mixture of mafic and sialic material is heated to the point of
melting and then allowed to cool, the mafic minerals will crystallize first, and being
denser than the sialic material, will separate downwards in the melt from the still molten
sialic materials on top….
B. Formation of Continental (Sialic) Plates:
Continental Accretion
As more crustal movement occurred, as the less dense sialic material was pushed against
the denser mafic materials, the denser mafic material would become subducted or
pushed downwards, underneath the sialic materials, thereby melting as it was subducted,
the hot magma rising upwards through the sialic materials forming island arcs
(“clumps” of sialic material). The formation of the island arcs perpetuated the refining
processes of partial melting and fractional crystallization.
Continental accretion-material literally scraped off oceanic
plate and ‘accreted’ to continental plate…accretion=growth!
Related to subduction of oceanic plate beneath continental
Chp10: Earth Interior
1.As the less dense sialic “clumps” formed on the earth’s surface, spreading centers
(divergent “cracks” in the earth’s surface) pushed the sialic materials together forming
larger masses of sialic “chunks” in a process known as Continental Accretion.
2. This caused a fusion of the early sialic materials into Sialic or Granitic Continental
Plates.
3. This also accounts for the composition of the continental plates as being High Grade
Metamorphic Terranes (metamorphic rocks are formed under intense heat and
pressure, the conditions during continental accretion).
Three basic questions that geology can help to answer (specifically using what we know
about the Earth’s Interior):
1.
2.
3.
What is the origin of the Earth’s atmosphere?
What is the origin of the water in the oceans?
What is the origin of life on Earth?
Chp10:
Earth
Interior
Other Aspects of the Earth
VI. The Atmosphere
a. Prior to 4.5 BYA – The atmosphere consisted of hydrogen, methane, ammonia,
hydrogen sulfide, nitrogen, argon, and water vapor.
b.4.5 BYA to 3.0 BYA – The atmosphere consisted of nitrogen, argon, water vapor,
CO2, and sulfur dioxide.
c. 3.0 BYA to Today - The atmosphere consists approximately of 78% nitrogen,
20% oxygen, with the remaining 1-2% argon, water vapor, CO2, and minor
gasses.
How is it known that the early atmospheres were composed as mentioned above?
Where did the other gasses go? Where did oxygen come from?
Evidences of the early atmospheres:
It is thought that all planets had at their formation atmospheres similar to the
Jovian planets of today. Because of solar winds, the volatile gasses (hydrogen,
methane, ammonia, hydrogen sulfide, sulfur dioxide, etc.) were blown off of the
inner terrestrial planets, leaving the rocky core.
Chp10: Earth Interior
By studying the composition of the atmospheres of the Jovian planets today,
geologists can derive the conditions of earth’s early atmosphere.
1. Banded Iron Formations – In certain areas there have been igneous activity
resulting in formations of layers of iron interspersed between layers of other
materials (i.e. silica) that have formed at the earth’s surface. Those banded iron
formations that date before 3.0 BYA are composed of elemental, un-oxidized iron,
indicating that they formed in an atmosphere devoid of free oxygen. Those banded
iron formations that date younger than 3.0 BYA consist of iron that is oxidized
throughout. This indicates that these younger iron layers formed in an atmosphere
rich enough in oxygen to cause the complete oxidization of the iron. Hence, prior
to 3.0 BYA there was not much free oxygen in the earth’s atmosphere, after 3.0 BYA
there was. (BYA = Billion years ago…)
2. Oxygen is not given off in substantial amounts by volcanic activity today…so
where did it come from? One source is photochemical dissociation. This occurs
whenever oxygen-bearing chemical compounds in the upper atmosphere are
subjected to cosmic radiation (background radiation from the Big Bang,
solar radiation, etc.) and break apart releasing their oxygen atoms.
This accounts for some of the “free” oxygen in the atmosphere, but not all. The
other great source of oxygen is photosynthesis.
Banded Iron Formations
Chp10: Earth Interior
This is the process whereby plants or plant-like organisms take in CO2 and H2O,
and in the presence of sunlight convert these compounds into sugars thereby
releasing free O2 into the atmosphere.
Photosynthesis is a series of chemical reactions that convert sunlight energy into
chemical energy. The processes occur in the chloroplasts of plants and algae. The
components for raw photosynthesis are water, CO2 , and light energy. The formula
for photosynthesis is:
light energy & chlorophyll
6CO2 + 12H2O ----------------------- C6H12O6 + 6O2 + 6H2O
The oldest known photosynthetic organisms, and the oldest known fossils, are
Stromatolites. These are inter-tidal blue-green algae with the oldest to date is 3.6 BYA
VII. The Hydrosphere and the Hydrologic Cycle
Where did the free water on earth come from?
As magma is formed within the earth, chemical compounds begin to bond eventually
forming various compounds and minerals. Many of these compounds contain water –
H2O as part of their makeup.
Stromatolites-ancient and recent.
note the bulbous, concentric
growth patterns
1.80BYA-Side view
Shark Bay, Australia ..growing today
Saratoga Springs, NY
500 MY old-top view
Chp10: Earth Interior
Sometimes a crystal lattice (a tinker-toy like structure of bonding atoms) contains
enough space within its 3-diminsional structure for water molecules to “fit”.
Origin of the oceans…..
1. out gassing- As magma rises to the earth’s surface and is released on the surface as
lava, the water escapes as steam.
2. As the steam cools in the atmosphere, water precipitates into clouds of water vapor.
As these clouds cool, they loose their water as rain or other forms of water precipitation
upon the surface of the earth. This volcanic out gassing is the source of most of the free
water that comprises the oceans, lakes, rivers, etc. Over the time of earth’s existence,
volcanism has out gassed enough water to fill the low-lying areas forming ocean basins.
3. Rainwater is naturally acidic, having a pH of about 5.5 to 6.5. As it hits the rocks and
minerals on the surface of the earth, it is a major source of weathering and erosion of
earth materials. As it runs down to the low-lying areas, it accumulates. As the sun
evaporates the water, it rises as water vapor, forms clouds and this Hydrologic Cycle
continues again and again.
…the whole process is constantly occurring, repeating itself through geologic time…
Chp10: Earth Interior-Summary
I. The Earth consists of three concentric layers:
a. the core: iron and nickel, 2 parts-solid inner, liquid outer; very dense
b. the mantle: lower, upper=Asthenosphere, lower Lithosphere; Lithosphere
c. the crust: Continental and Oceanic:
1. Continental Crust – (20 – 90 km thick) this material comprises most of the
continental plates. It has a density of 2.7 grams/cm3 and is rich in silica, aluminum.
This type of rock material is referred to as being “Sialic” or “Felsic”= granite.
2. Oceanic Crust – (5 – 10 km thick) has a density of 3.0 grams/cm3 and is largely
comprised of the igneous rock Basalt, which is rich in iron and magnesium.
This type of rock material as referred to as being “Mafic” or “Basaltic”.
II. Refinement of Earth’s Crust- 2 processes
a. Partial melting: hot mantle plumes rise within Mantle heating (i.e. partial melting) the
material. Mafic minerals denser so they settle out, leaving less dense sial minerals behind.
b. Fractional crystallization: Mafic minerals crystallize at higher temperatures than Sialic
minerals, so Mafic minerals will crystallize first and separate from Mafic minerals
III. ‘Growth’ of Continental Plates by accretion
Process related to subduction of oceanic plate beneath continental plate. Sediments and basal
literally scraped off subducting oceanic plate, plastered to edge of continental plate. Essential
this material is ‘glued’ to the edge of the continental plate, resulting in that plate ‘growing’…
Chp10: Earth Interior-Summary
The Interior of the Earth gives us some clues as to the origin of:
I. Atmosphere
a. Evolution of gases through time- evidence in Banded Iron Formations. Generally some of
oldest rocks on surface of Earth (1.0 BY or more….)
b. Photosynethesis- stromatolites are evidence of bacterial action very early in preCambrian
600+ MYA
II. Hydrosphere
-Water originally came from volcanic activity- steam associated with outgassing as lava
is extruded onto surface of Earth.
-Steam is converted into water vapor in atmosphere.
-Water vapor condenses in atmosphere and falls back to surface of Earth as rainfall, which
erodes rocks
-Water accumulates in rivers and streams, is evaporated by sunlight as water vapor into atmosphere and the entire process begins again…..The Hydrologic Cycle….
Chp10: Earth Interior-Summary
III. The Biosphere
The smallest particles are atoms which combine together to form molecules, which are the basic
building blocks for all elements
1.The basic elements that serve as nutrients for life are derived from the Earth’s Interior and sunligh
2.These elements combine to form molecules,
3.Molecules combine to form cells, which are the basis for all Life as we know it…
4.These cells form tissues, which in turn combine to form organs.
5.Organs work in conjunction to form systems (circulatory, respiratory, muscular,
etc.), and all of the systems together form the organism, the entity.
6.All organisms of the same species in a geographic area are called a biologic community
7.All of the biologic communities in a geographic area are called a biologic population.
8.All of the populations in an area interact with the abiotic (non-living aspects – soil,
air, sunlight, etc.) to form an ecosystem.
9.All of the ecosystems on earth interact to collectively form the ecosphere or
biosphere.
Chp 6: Sedimentary Rocks- Summary
A. Sedimentary Rocks are derived from weathering of igneous rocks
B. Two types of Sedimentary rocks:
-Chemical precipitates: Calcium carbonate
-Clastic rocks: sandstones, shales, etc.
C. 4 Steps to Formation of Sedimentary Rocks:
-Erosion: various weathering processes
-Transportation: air, glaciers, running water, etc
-Deposition
-Compaction: overburden, burial
D. Characteristics of Clastic Sedimentary Rocks
-Roundness: well rounded vs angular
-Sorting: well sorted vs poorly sorted
-Color: red=exposed to air; glauconite=green=marine
-Particle Size (see following diagram)
Table 6-1, p.152
Chp 6: Sedimentary Rocks- Summary
II. Chemical Precipitates
-Limestone: calcium carbonate
- Dolostone: calcium and magnesium carbonate
-Bioclastic deposits: form around remains of marine organisms.
e.g. chalk, coquina (shells),
-Evaporites: halite, gypsum, etc. Evaporitic conditions
-Coal: peat, lignite, bituminous coal, anthracite
Bedding/Layering of Sedimentary Rocks
-Aeolian: wind, cross bedding
-Fluvial: cross bedding, laminations, etc.
-Turbidites: graded bedding.
-Marine: currents-ripples
-Marginal marine to terrestrial: mud cracks
Laws of: Superposition and horizontality: oldest on bottom, flat
Chp 6-Sedimentary Rocks: Summary
Vertical Succession of Facies
-Transgressive: sea level rise
-Regressive: sea level fall
Economic Uses of Sedimentary Rocks:
-iron ore from fluvial deposits
-placer (fluvial) deposits: precious minerals-gold and silver
-Drilling for hydrocarbons (oil and gas)
stratigraphic traps, structural traps, salt domes
-gravel pits for road use
Chp 7- Metamorphic Rocks-Summary
Metamorphic Rocks form as a result of ‘metamorphism’…an alteration of rock characteristics and chemical composition due to application of heat and/or pressure, or chemically active fluids.
“Parent rock” is term applied to the rock being metamorphosed-it may be igneous, sedimentary or even another metacmorphic rock.
Metamorphic rocks commonly occur in-core of mountain ranges
-continental shields (sedimentary rocks commonly deposited on top of them…)
-original continental accretion in PreCambrian
Factors applied during metamorphism:
-Heat
-Pressure
-Chemically active fluids
Table 7-1, p.192
Chp 7- Metamorphic Rocks-Summary
Types of Metamorphism:
A. Contact metamorphism: results from heat and fluids
-metamorphic ‘halo’ known as aureole is generated (shale)
-baked zones common
-hydrothermal effects occur..
B. Regional burial: occurs over large area
-gradation of minerals common as a result of high pressure
-specific minerals indicate different levels of pressure/temperature
C. Dynamic metamorphism: usually associated with fault zones
- mylonites
Economic uses- mining slate, hydrothermal minerals suggest proximity
to gold or silver??
Chp 7- Metamorphic Rocks-Summary
Metamorphic textures:
A. Foliated-results from contact metamorphism
-varies from coarse to fine
slate, phyllite, schist, gneiss, amphibolite, migmatite
B. Non-Foliated- no preferred orientation to minerals
-2 types: single mineral, grains too small to be seen with naked eye
marble, quartzite, greenstone, hornfels, anthracite
Metamorphic Zones/Facies: metamorphic rocks characterized by
specific mineral assemblages that reflect pressure-temperature regime
rock experienced:
1. Greenschist: contain chlorite, low temperature, lo pressure
2.Granulite/Amphibolite: similar but higher pressure
3. Blueschist: fairly low temperature, high pressure. Indicative of
subduction zones. Glaucophane mineral….
Metamorphic facies produced along oceanic-continental boundary
Fig. 7-19, p.201
Summary
• Early Christian theologians viewed time
– as linear and decided that Earth
– was very young (about 6000 years old)
• A variety of ages for Earth were estimated
– during the 18th and 19th centuries
– using scientific evidence,
– ages now known to be too young
• Neptunism and catastrophism were popular
– during the 17th, 18th and early 19th centuries
– because of their consistency with scripture,
– but were not supported by evidence
Summary
• James Hutton viewed Earth history
– as cyclical and very long
– His observations were instrumental
– in establishing the principle of uniformitarianism
• Charles Lyell articulated uniformitarianism
– in a way that soon made it
– the guiding doctrine of geology
• Uniformitarianism holds that
–
–
–
–
the laws of nature have been constant through time
and that the same processes operating today
have operated in the past,
although not necessarily at the same rates
Summary
• The principles of superposition,
–
–
–
–
–
original horizontality,
lateral continuity
and cross-cutting relationships
are basic for determining relative geologic ages
and for interpreting Earth history
• Radioactivity was discovered
–
–
–
–
during the late 19th century
and lead to radiometric dating,
which allowed geologists
to determine absolute ages for geologic events
Summary
• Types of unconformities– A disconformity is a surface
• separating younger from older rocks,
• both of which are parallel to one another
– A nonconformity is an erosional surface
• cut into metamorphic or intrusive rocks
• and covered by sedimentary rocks
– An angular unconformity is an erosional surface
• on tilted or folded strata
• over which younger rocks were deposited
– Hiatus= interval of time NOT represented by rock
record
Summary
• Geologists determine how many half-lives
– of a radioactive parent isotope
– have elapsed since the sample crystallized
• Half-life is the length of time
–
–
–
–
it takes for one-half
of the radioactive parent isotope
to decay to a stable daughter isotope
of a different element
Summary
• The most accurate radiometric dates
–
–
–
–
are obtained from
long-lived radioactive isotope/daughter pairs
in igneous rocks
Common pairs include:
•
•
•
•
•
uranium 238 – lead 206
uranium 235 – lead 207
thorium 232 – lead 208
rubidium87 – strontium 87
potassium 40 – argon 40
Summary
• The most reliable radiometric ages
– are obtained using two different pairs
– in the same rock
• Carbon 14 dating can be used
–
–
–
–
only for organic matter such as
wood, bones, and shells
and is effective back
to about 70,000 years
Chp 9: Earthquakes
STUDING THE INTERIOR OF THE EARTH
A. Seismic Tomography
1. Geologists use seismic waves to study the interior of the Earth
2. Properties of waves
a. In a uniform homogeneous medium, a wave radiates velocity
b. The velocity of a seismic wave depends on the nature of the material that
travels through; i.e. its rigidity and density
c. When waves pass form one material to another, they refract (bend)
d. P-waves are compressional waves and travel through all media—gases,
liquids, and solids—whereas 3-waves are only transmitted through solids.
3. In a uniform and homogeneous Earth waves will radiate form the focus of an
earthquake in concentric spheres and travel uniformly through the planet. Uniform
propagation of waves is not observed
B. Discovery of the core
1. Shadow Zone
a. No direct waves are defected beyond 105 degrees from the focus
b. Caused by a discontinuity deep in the interior of the Earth
c. The shadow zone exists because of refraction of the p-waves at the mantle-core
boundary and the failure of s-waves to pass through
Chp 9: Earthquakes
2. The failure of s-waves to pass through the outer core, and the refraction of p-waves
shows that the core is composed of an inner solid sphere surrounded by an outer liquid
sphere
C. Discovery of the Crust-Mantle Boundary
Mohorovicic Discontinuity (Moho): the boundary between the crust and the mantle
was first identified as the boundary between different types of rock that transmit waves
at different velocities.
THE EARTH’S INTERIOR
Seismic Tomography: The study of the Earth’s interior indirectly by studying the
action of seismic waves.
This information was discovered by seismic interpretation
A. The Crust
1. The outer shell of the Earth
2. Oceanic crust
7-10 km thick
-p-waves travel through oceanic crust (basaltic composition) at 7 km/sec
3. Continental crust
-20-70 km thick
-p-waves travel through continental crust (granitic composition) at 6km/sec
Chp 10: Earth’s Interior
Chp 9: Earthquakes
B. The Mantle
1. 2900 km thick and comprises about 80% of the volume of the Earth
2. Large quantities of basalt magma originate in the mantle
3. The layers within the mantle
a.Upper mantle
--Extends from the base of the curst downward to about 670 km beneath the surfa
--composed primarily of peridotite
-- subdivided into three layers
1. lithosphere—crust and uppermost part of the mantle—where most
earthquakes occur
2. asthenosphere – extends from the base of the lithosphere to a depth
of 350 km
3. low-velocity layer—separates lithosphere form asthenosphere
C. Outer Core – known to be liquid because of the behavior of seismic waves. It is
speculated that the material is liquid iron and nickel.
D. Inner Core – known to be solid because of the behavior of seismic waves and is
thought to be solid iron and nickel.
Chp 9: Earthquakes: Summary
Earthquakes – causes of ….and locations of…
a. release of accumulated stress along faults
b. commonly occur along plate boundaries: circum-Pacific and
Mediterranean region
Earthquakes: location determined bya. minimum of 3 operating seismograph stations
b. measure travel time to each station, plot distance as radius of circle
c. where 3 circles intersect is the Epicenter-the location on the surface
of the Earth directly above earthquake center
Earthquake energy transmitted as WAVES…various types of waves:
a. P waves: primary, distort grains parallel to motion of wave
b. S waves; secondary, distort grains perpendicular to motion of wave
Tonga volcanic arc, Pacific O: focal depth increases in well-defined
Zone that defines subducting oceanic plate…called Benioff Zone….
Subducting oceanic plate…
Fig. 9-5, p.248
Chp 9: Earthquakes: Summary
Types of S waves: (surface)
a. Rayleigh waves: material distorted in elliptical path
b. Love waves: side to side motion
Richter Scale:
a. an increase of 1 unit on scale represents 10 fold increase in amplitude
b. an increase of 1 unit on scale represents 30 fold increase in energy
Seismic gap: useful for prediction today (not accurate)
a. An immobile region of a fault bounded by moving segments
b. Rock within the seismic gap is accumulating elastic deformation and will
eventually fracture producing a major earthquake
Other predictive tools:
a. foreshock swarm intensity increases dramatically
b. radon gas increase
c. animal behavior
Chp 9: Earthquakes: Summary
Propogation of seismic waves from earthquakes has greatly aided our
understanding of composition of interior of Earth:
A. The Crust
1. The outer shell of the Earth
2. Oceanic crust
-7-10 km thick
-p-waves travel through oceanic crust (basaltic composition) at 7 km/sec
3. Continental crust
-20-70 km thick
-p-waves travel through continental crust (granitic composition) at 6km/sec
B. The Mantle
1. 2900 km thick and comprises about 80% of the volume of the Earth
2. Large quantities of basalt magma originate in the mantle
3. The layers within the mantle
Chp 9: Earthquakes: Summary
a.Upper mantle
--Extends from the base of the curst downward to about 670 km beneath the surface
--composed primarily of peridotite
-- subdivided into three layers
1. lithosphere—crust and uppermost part of the mantle—where most
earthquakes occur
2. asthenosphere – extends from the base of the lithosphere to a depth o
km
3. low-velocity layer—separates lithosphere form asthenosphere
C. Outer Core – known to be liquid because of the behavior of seismic waves. It is
speculated that the material is liquid iron and nickel.
Inner Core – known to be solid because of the behavior of seismic waves and is
thought to be solid iron and nickel.
Chp 10: Earth’s Interior
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Chp 10: Earth’s Interior
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Interactions in Earth’s
Subsystems
Gases from
respiration
Transport
of seeds and
spores
Chp10: Earth Interior
VIII. The Biosphere: The Organization of Life on Earth
The biosphere is the term for all of the living aspects of the earth.
1.All life as we know it is composed of atoms of various elements.
2. These atoms bond in various ways to form molecules.
3.Certain molecules make up cells, or the basic unit of life. This is called so
because the cell exhibits all of the aspects that we consider to be living (atoms and
molecules are not considered to be alive).
4. Certain cells work together to form tissues, and various tissues together form organs.
5.Organs work in conjunction to form systems (circulatory, respiratory, muscular,
etc.), and all of the systems together form the organism, the entity.
6. All organisms of the same species in a geographic area are called a
biologic community.
7. All of the biologic communities in a geographic area are called a
biologic population.
8. All of the populations in an area interact with the abiotic (non-living
aspects – soil, air, sunlight, etc.) to form an ecosystem.
9. All of the ecosystems on earth interact to collectively form the ecosphere or
biosphere.
Chp10: Earth Interior
When an organism dies, certain bacteria and fungi (ecological decomposers) break down
the organism back into molecules and atoms that are put back into the ecosystem for other
organisms to use. The calcium in your bones came from foodstuffs (i.e. milk) consumed
during your life. The milk containing the calcium came from the cow…the cow got the
calcium from the grass consumed…the grass got the calcium from absorbing it from the
soil…the soil formed from the weathering and erosion of calcium containing rocks and
minerals, that came from the earth in the form of cooling magma or lava. Or the calcium
in the soil could have come from the decomposition of the skeleton of some previous
living organism…You may have calcium in your bones that once was incorporated into
the skeleton of a dinosaur!!!