CHAPTER 6: THE LITHOSPHERE & THE HYDROSPHERE
(1) THE LITHOSPHERE
•Approximately 100 km thick
•The outer shell is made up of the Earth’s crust and the top part of upper mantle
•It contains minerals & rocks
1.1 MINERALS
Inorganic, neither animal nor plant; found in nature; for most, atoms are
organized in a set pattern (ex. salt crystals), fig. 6.2 (p.185); elements (ex. Au gold) or compounds (ex. Cu SO4 - copper sulfate); 4000+ different minerals;
common: feldspar, quartz, mica…; rare (precious): diamonds, rubies, emeralds…
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MINERAL CLASSIFIACTION
They are classified according to the following properties:
•Idiochromatic
•Allochromatic
minerals - have a characteristic color
minerals - color varies; would be colorless but diverse impurities
add different colors, ex. Quartz
•Transparency: degree to which light passes through; 3 levels, from complete to
none:
1)Transparent (ex. rock crystal, regular glass)
2) Translucent (ex. olivine, frosted glass)
3) Opaque (ex. pyrite, solid black plastic)
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- HARDNESS: dependent on bond strength of atoms
-Mohs scale indicates hardness
1 (very soft; easily scratched by nail; ex. talc)
10 (very hard; can scratch all others; ex. diamond)
- a higher level (ex. quartz: 7) can scratch all levels lower than itself, i.e. levels 1-6
- hardness is important for jewelers, for cutting and polishing
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-STREAK:
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A mark left by a mineral on a slab of unglazed porcelain; a char. of minerals;
idiochromatic minerals leave brightly colored streaks/powder; allochromatic minerals
leave white /pale streaks
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-MINING
- Ore: the material (rock) extracted from the lithosphere; contains a desired mineral
- Deposit: site that contains a high concentration of a certain mineral
-Qc has Au, Cu, Zn, Ni, and Fe deposits; most active region: Abitibi-Témiscamingue
region (Rouyn-Noranda), fig. 6.8 (p.187)
- Mining: complex; costly; Open-pit mine: if deposit is near surface; if deposit is too
deep: underground passages, including a huge vertical shaft, drifts (horizontal tunnels,
air ducts, & water supply lines) must be built
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1.2 ROCKS
Rocks are heterogeneous solids composed of more than one mineral
-There are three types:
(1) IGNEOUS: made of cooled lava
There are two types:
a) EXTRUSIVE:
lava cools when it comes in contact with air; ex. rhyolite,
obsidian, basalt
b) INTRUSIVE:
magma solidifies underground; ex. granite, basalt (occurs
both ways)
(2) SEDIMENTARY: the erosion of plant and animal debris falls into water forming
layers that compact over time; ex. evaporates, sandstone, limestone, shale
(3) METAMORPHIC: igneous/sedimentary rocks change when subjected to high
temperatures and pressure; ex. limestone can change into marble, granite into gneiss,
shale into slate, jadeite-rock usages table 6.15 (p.191)
Formation of igneous rocks
Formation of igneous
extrusive rocks
Magma intrusion
Formation of igneous
intrusive rocks
Volcano
Magma
Igneous
rocks
form
from
magma
Pumice rock is a type of extrusive rock.
It is magma that cooled quickly while
being thrown into the air during a
volcanic eruption. This rock contains so
many bubbles of air that its density is
lower that water. It floats when placed
in water.
Obsidian is an igneous extrusive rock
that has a glossy structure.
Rhyolite is an igneous extrusive rock
that has a fine grain structure.
Gabbro is an example that shows many
different colours of minerals.
Diorite is similar to gabbro, but its
colours are lighter.
1.3 SOIL
Originates from the PARENT ROCK which
is part of the Earth’s crust; soil is made
up of SOIL HORIZONS, parallel and
horizontal layers which are represented
by capital letters in the diagram right; fig.
6.16 (p.192); notice how color darkens
as more organic matter is present
- soil formation takes ~ 200 years!
-Steps & Layers:
(1) PARENT ROCK is stressed by frost, wind, & rain.
(2) The parent rock becomes the LITHOSOIL which is made up of large pieces of
disintegrating parent rock; light colored and coarse. Lithosoil is mixed with humus
(organic matter from decaying plant & animal matter)
(3) The lithosoil produces a series of physical & chemical reactions that lead to the
formation of SUBSOIL (small mineral particles, tree roots tips, darker & pieces of rock
become smaller)
(4) TOPSOIL is made of darker, humus rich, light, air pockets, water soluble minerals,
plant roots which can sustain plant life.
(5) ORGANIC MATTER is the most superficial layer and it is mostly humus
- the more humus a layer has, the more nutrients and small organisms it will contain
- to be able to sustain life, soil must contain: a sufficient amount of minerals, moisture
and an adequate pH level that promotes mineral absorption
HUMUS, organic matter that has
decayed to a relatively stable,
amorphous state. Humus is formed
by the decomposing action of soil
microorganisms (e.g., bacteria and
fungi), which break down animal and
vegetable material into elements that
can be used by growing plants.
Because of its low specific weight and
high surface area, humus has a
profound effect upon the physical
properties of mineral soils with
regard to improved soil structure.
Not that humus!
Degradation of the
mother-earth
Parent-earth
From left to right, we can
see the evolution of the
soil: the main ground
floor
(Mother-earth)
begins
to
gradually
degrade.
-BUFFERING CAPACITY:
is the ability to withstand changes in pH when
acidic/alkaline substances are added to the topsoil
- Plants prefer pH levels between 6 & 7; conifers prefer more acidic soil
- A soil can neutralize (buffer) itself to a certain point, this protects it from
changes in pH
- best buffer: fine soil components, ex. organic matter & clay
1.4 PERMAFROST
Soil that has been solid for more than two years; 50% of Canada’s land; up to 500 m
deep; it is found in polar regions or higher in altitude; top layer can thaw in summer
(active layer); agriculture is impossible and construction difficult since permafrost
softens easily if temperature rises.
1.5 ENERGY RESOURCES
-FOSSIL FUELS: coal, natural gas and oil; they come from the transformation of organic
residue.
- Oil: originates from dead marine animal and algae that sank to the ocean floor &
transformed to oil over time as the pressure of upper layers caused the change; fig.
6.22 (p.196); considered nonrenewable since millions of years are needed for its
formation.
-Coal: originates from terrestrial plant and trees that grew in swamps; plant debris
became covered by layers of sand and silt which continued to accumulate over time,
the pressure of which compressed the residues to coal (solid)
- Burning fossil fuels emits thermal ener. (from chemical bond breakage) which is
converted into electrical or mechanical ener.; combustion causes greenhouse gases &
acid rain
-URANIUM: naturally occurring in Earth’s crust; radioactive element; nuclear ener. is
produced when the nucleus is split releasing ener. stored by nuclear particles; nuclear
ener. can be converted to electricity
-greenhouse gases not produced during nuclear ener. formation, rather produces heat
& radioactivity (a serious health risk)
-even if nuclear reactors are encased in reinforced concrete, accidents & leaks can still
occur
-nuclear waste also produced & no neutralization methods exist; waste is cooled &
buried in special pits or old mines
- in Qc only 1 nuclear plant: Gentilly-2 in Bécancour near Trois-Rivières
(Gentilly-2 has been in operation since 1983 & supplies only 3% of Qc’s ener. Many
disapproved of last year’s planned renovations since it is widely believed nuclear ener.
is dangerous and not necessary with all the hydro power our province possesses. It is
expected that the plant will stay closed for the next 3 to 5 years due to the ongoing
renovations.)
- GEOTHERMICS
- molten rock inside the Earth produces intense heat called geothermal ener.;
specialized underground piping contains water which is heated; when water rises to
the surface, the heat is captured & converted to electricity or used to heat homes
- often found in volcanic areas, ex. Iceland, fig. 6.24 (p.198); would be too expensive to
set up in North America
-ENERGY OF TOMORROW?
- the world is running out of fossil fuels (est. Peak Oil has been reached); nuclear
power is risky & geothermal is too expensive; clean alternatives are needed
- researchers are trying to use H (very abundant) & O2 to produce electricity but no
solutions have been found yet
1.6 POLLUTION & DEGRADATION
-SOIL DEPLETION: heavy farm machinery compacts the soil, making O2 it contains less
available & preventing water from entering; water & water-soluble minerals are
washed away & don’t reach vegetation, result: soil is infertile
-land is over farmed preventing natural regeneration forcing the use of more fertilizers
to compensate; excessive fertilizer use can lead cyanobacterial (algal) blooms
- pesticides used threaten BIODIVERSITY since they accumulate in tissues of organisms
causing problems
- CONTAMINATION: the abnormal presence of harmful sub’s in the enviro.; ex.
hydrocarbons from gas stations; heavy metals from landfills; acid residue from mining,
etc; acid rain sends atmospheric pollutants to the soil, which can be disastrous to
ecosystems since organisms cannot neutralize all the acidity
(2) THE HYDROSPERE
- Earth’s outer water layer; includes all phases of water (S-L-G)
-97.5% salt water & 2.5% freshwater; incl. oceans, rivers, lakes, streams, ponds…
2.2 THE OCEANS
- continents divide waters into 5 oceans: Pacific. Atlantic, Indian, Arctic, & Southern
(above Antarctica)
- powerful currents move the water across the oceans
- important factors that influence water T:
1.
Depth (fig. 6.29, p.203); 3 main water levels exist:
(1) Mixed layer: 0-200m; warmed by the sun; depth varies depending on waves, tides,
& turbulence; T: ~27°C
(2) Thermocline: 200-1000m; transition zone since sun can’t reach these depths; T: 527°C
(3) Deep water: 1000-4000m+; very cold water; T: 4-5°C
2. Seasons: water less affected by T changes than land; water has a moderating effect,
meaning it can “absorb” T changes before a real degrees change is recorded
3. Latitude: Equator water T bet. 25-28°C; temperate zones (ex. Canada) T bet. 1217°C
4. Salinity: aver. 3.4%-3.7% salt; as waves crash against rocks, mineral (salts) are
dissolved into it, salinity weakest near poles (almost 3%) where glaciers dilute salt
content; in Red Sea (right) salinity is 4% due to high heat, evaporation rate, & drought
-OCEAN CIRCULATION: combined effects of all currents; water is in constant motion
(both at surface & deeper) due to waves, tides, & circulation; ocean circulation is
comprised of 3 types of currents or circulations:
1.
Surface currents: 0-400m deep; move horizontally; wind-driven; ex. Gulf Stream,
starts near Equator & carries warm Atlantic waters from the lower US area
northwards
2. Subsurface currents: >800m deep; wind has no effect; water driven by: density
(denser water sinks below more buoyant waters), T (colder waters sink because they
are denser, ex. Arctic waters are cooled by the air thus creating movement when they
sink, salinity (the higher the salinity, the denser the water, ex. in hot regions there is
more evaporation therefore an increased salinity occurs, denser more saline waters
sink creating circulation
3. Thermohaline Circulation: thermo (T) & haline (salt); this is a huge conveyor belt that
circulates the world’s waters; fig.6.31 (p.206); it helps moderate (decrease) the diff. in T bet. the
poles & the Equator; without it climates would be drastically affected, i.e. poles would be even
colder & Equator even hotter – this would be catastrophic
This is how some of our garbage migrates incredible distances, by means of ocean circulation, &
ends up in the food chain, ultimately killing animals and even disrupting our endocrine systems
as we consume affected animals. This problem is linked to human disease and infertility.
2.4 ENERGY RESOURCES
-Hydraulic ener: tremendous amounts of ener. harnessed from moving water
-WATER FROM RIVERS & WATERFALLS
-in Qc the rate of flow of rivers is impressive, this represents +++++ener.; most of Qc’s
electricity comes from hydroelectric power plants
-How? (1) Dam is built across a river. (2) Water leading to the dam rises creating a
reservoir. Dam needs to be strong to hold water back. (3) Dam gates are opened &
water enters pipes & reaches turbines. (4) Force of water turns turbines which are
connected to alternators that convert mechanical ener. produced by water into
electricity. (5) Electricity is then distributed to homes & buildings
- hydraulic dams convert hydraulic ener. into electricity (below)
- hydroelectric power – renewable ener.; unfortunately ecosystems suffer when hugh
areas are flooded by the dam; waters are distributed by the dam’s actions & Hg (highly
toxic) found in riverbed soil is lifted & converted into methylmercury by bacteria. In
this form Hg, which is a by-product of industrial activity, can enter the food chain (fish
to humans); Hg is a powerful neurotoxin that can also affect the intestines & kidneys
Methylmercury sinks to the bottom,
becoming part of the sediments, and
slowly makes it way up the food
chain (below). (This is an example of
bioaccumulation.)
- WAVES & CURRENTS: contain large am’ts of ener.; scientists are trying to develop
ways of harnessing this ener.; expensive technology, still prototypes, ex. underwater
turbine (below)
2.5 POLLUTION & DEGRADATION
-chemicals discharged in water a problm
-Thermal pollution: the discharge of warm water also a prblm since O2 solubility
decreases with increasing T
- THE CONTAMINATION & EUTROPHICATION OF NATURAL WATERS: process by which
waters experience O2 loss due to extensive accumulation of organic matter & nutrients
- Point Source: pollution is traced to a specific site & a non-point source is traced to an
area, ex. rain spreading chemicals coming from a farm
- when the am’t of pollutants is too great, organisms (bacteria, protozoans...) can no
longer neutralize the toxins & a detrimental effect begins; i.e. the aquatic system
becomes polluted when it loses its balance .& when contaminants persist; fragile spp.
(ex. frogs since they have permeable skin) & drinking water are now at risk
- impact is related to the nature & concen. of the contaminants; slow moving waters
more at risk since contaminants stagnate
- N & P containing pesticides & fertilizers (from farming) run off into lakes & rivers
when it rains; this causes excessive algal growth (or cyanobacterial growth – called
both) & leads to O2 depletion & eutrophication
- Eutrophication is usu. a natural aging process a lake goes through (below); this
process can be greatly accelerated by man, taking place within mere decades instead
of several hundred years
- when algae dies, it sinks to the bottom; bacteria consume the dead algae & use high
quantities of O2 in the process; fish & other organisms die off since there isn’t enough
O2 for their survival & eventually the lake dies (accelerated eutrophication is called
cultural eutrophication since it is man-generated)
-THREATS AT SEA
-although oceanic waste dumping has been banned since 1972 (London Convention), it
still occurs, ex. 6 million tones of petroleum are discharged in oceans every year & very
little of this is accidental (from offshore drilling platforms, oil tankers cleaning their
reservoirs at sea, etc)
- hydrocarbons float on water & coats marine animals & poisons them; hydrocarbons
can be decomposed by bacteria but this takes years