Download CH. 8 EARTH SYSTEMS

Chapter 8
Earth Systems
Hybrid Electric Vehicles
Although they reduce
our consumption of
liquid fossil fuels, HEV
do come with
environmental tradeoffs. They require scarce
metals for the motors
and the batteries.
Mining of these metals have severe environmental impacts
such as adding acid, as well as harmful levels of metal to
waterways, erosion of soil, and creates habitat destruction.
Earth’s Resources
• Most of the elements that we have on earth
came from when the earth was first formed 4.6
billion years ago.
They were distributed unevenly around the
globe.
Earth’s elements settled into place based on
their mass leading to distinct vertical zonation.
Earth’s Layers
The core is made up of Ni and Fe. The
inner core is solid and the outer core is
liquid. The mantle contains magma
that slowly circulates in convection
cells. The asthenosphere is composed
of semi-molten, ductile rock. The
Lithosphere, is a brittle outermost
layer of the planet about 100km thick.
It includes the solid upper mantle as
well as the crust. Over the crust lies
the thin layer of soil that allows life to
exist on the plant.
The crust and the overlying soil
provide most of the chemical elements
that compromise life.
Earth contains a finite supply of
mineral resources
• We can’t extract indefinitely!
• Since we have already mined the
most easily obtainable minerals,
more energy must be used to extract
the remaining resources.
Mineral Distribution around the world
Earth is constantly changing
• The core of the earth is very hot as a result of
radioactive decay of various isotopes such as K, U,
and Th which releases heat.
• The heat causes plumes of magma to well
upward from the mantle to the lithosphere and
create hot spots.
• The heat from the core also creates convection
cells in the mantle that drives change and
creation and renewal of Earth’s matrials in the
Lithosphere.
Earth’s Tectonic Plates
Theory of Plate Tectonics
• World continents were originally one land
mass= Pangaea
• Earth’s Lithosphere is divided into plates,
most of which are in constant motion.
• The tectonic cycle is the sum of the processes
that build up and break down the lithosphere.
• Oceanic plates lie beneath the oceans
• Continental plates lie beneath landmasses.
Convection and Plate Movement
• Oceanic plates are more dense and rich in Fe.
• Continental plates contain SiO2, which is less
dense than Fe. So they are lighter than the
oceanic plates and typically rise above them.
• Both plates float on top of denser material
below them and move by convection cell’s in
the Earth’s mantle.
• As the plates move, the continents slowly
drift.
Convection Plate Movement
Tectonic Plates
Seafloor Spreading
• As Oceanic plates move apart, rising magma
forms new oceanic crust on the seafloor at the
boundaries between those plates.
• When Oceanic plates meet Continental plates,
old oceanic crust is pulled downward beneath
the continental lithosphere and the heavier
oceanic plate slides underneath the lighter
continental plate= subduction
Consequences of Plate Movement
• As the Continents drifted over time,
many changes occurred: climate
changes, geographic barriers formed,
species evolved or went extinct,
some continents broke apart, islands
formed, volcanoes formed, volcanic
islands formed.
Geologic Time Scale
Type of Plate Contact
• Divergent plate boundaries= when plates
move away from each other. Magma reaches
the Earth’s surface and pushes up and out
creating new rock= seafloor spreading.
• Convergent plate boundaries=plates move
towards each other and collide, creating
mountain ranges (Andes)
• Transform fault boundary= when plates move
sideways past each other.
Type of Plate Boundaries
A fault zone in California is created where
movement of the plates has occurred and rock
near the plates margin fractures
Earthquakes
• Earthquakes occur when the rocks of the
Lithosphere rupture unexpectedly along a fault.
• The epicenter is the exact point on the Earth’s
surface directly above the location where the
rock ruptures.
• Sometimes volcanic eruptions and earthquakes
are observed at the same time, along the plate
boundaries where tectonic activity is high.= Ring
of Fire, around the Pacific Ocean.
Locations of Earthquakes and
Volcanoes
Haiti Earthquake 2010 kills 200,000
The Richter Scale measures
the largest ground
movement that occurs
during an earthquake.
The scale is logarithmic, like
the pH sale. So a 7.0 on the
scale is ten times stronger
than a 6.0.
This earthquake registered
as 7.0 in magnitude
Volcanic Eruptions
• Spew ash into the air that contains SiO2.
• Dust, rock or lava , and cinder may cause a
loss of life, habitat destruction and alteration
and reduction in air quality.
THE ROCK CYCLE
Rocks
• The substance that the lithosphere is made of,
contains one or more minerals (solid
chemicals with uniform or crystalline
structures that form under pressure and heat).
• Rocks can form from molten magma, by
compression of sediments, and by exposure of
rocks and other materials to heat and
pressure
Igneous Rocks
• Form directly from molten magma
• Classified by their chemical composition as either
basaltic (dark colored-with high amounts of Fe,
Mg, and Ca, and is the dominant rock type in
oceanic plates or granitic(lighter coloredcomposed of feldspar, mica and quartz, Si, Al, K,
Ca and is the dominant rock type in continental
plates)
• Intrusive- forms within Earth as magma, rises up,
and cools in place underground.
• Extrusive-forms when magma cools above the
surface rapidly, so minerals have little time for
crystals to form; resulting in obsidian.
Sedimentary Rocks
• Form when sediments (mud, sand and gravel)
are compressed by overlying sediments.
• Takes a long period of time to form
• Ex: sandstone, conglomerate and mudstone
• Contain the fossil record of our past, with
plant and or
animals remains
that are compressed
over eons
Metamorphic Rock
• Forms when sedimentary rocks, igneous rocks,
or other metamorphic rocks are subjected to
high temperatures and pressures.
• Ex: Slate, marble, and anthracite
Weathering
• Physical Weathering- the mechanical breakdown of
rocks and minerals by water, wind, or variations in
temperature. It can also be caused by plant roots and
burrowing animals. It produces a greater surface area
for chemical weathering processes to work on.
• Chemical Weathering-the break down of rock and
minerals by chemical reactions, the dissolving of
chemical elements from rocks, or both. It releases
essential nutrients from rocks making them available
for use by plants and animals. Acid rain promotes
chemical weathering of certain minerals in the soil.
Erosion
• Erosion is the physical removal of rock fragments
from a landscape or ecosystem.
• This can occur by wind, water and ice transport
materials downslope under the force of gravity.
Organisms that burrow under he soil can also
cause erosion.
• Once the material has traveled a certain distance
it accumulates and deposition occurs.
• Erosion can be accelerated by deforestation,
overgrazing, road building and unmanaged
construction activity.
Soil Formation is the 3rd part of the
geologic cycle.
• Soil is a mixture of geologic and organic
components.
• Soil has many functions: plant growth,
primary filter of water, provides habitat for
bacteria, algae, fungi, insects and other
animals, breaks down organic material and
recycles nutrients that benefit plants and
filters chemical compounds.
Soil Formation
• Is formed over thousand of years as a result of
weathering of rocks and the accumulation of
detritus from the biosphere.
• Young soil has less organic matter and fewer
nutrients than a more mature soil.
• There are 5 factors that determine the
properties of soil: the parent rock, climate,
topography, organisms and time.
SOIL FORMATION
• Parent Material- the type of rock of which it was
composed of. Quartz-sand parent material
produces nutrient poor soil. Soil that has CaCO3
will have an abundant supply of Ca , have a high
pH and support a high agricultural productivity.
• Climate-soil does not develop well in
temperatures below freezing because organic
matter can’t decompose well then. Soil formed in
the tropics, is accelerated due to rapid
weathering of rocks and minerals, leaching of
nutrients, and the decomposition of organic
detritus.
• Topography- the surface slope and the
arrangement of a landscape. Soil that forms
on a steep slope is subject to erosion.
• Organisms-Plants remove nutrients from the
soil and excrete organic acids that speed
chemical weathering. Animals that burrow:
earthworms, gophers, voles, mix the soil
distributing organic and mineral matter.
• Time-As soil ages, and has organic matter in it
over time, they become deep and fertile.
SOIL HORIZONS
Soil Horizons (Layers)
• O Horizon- at the surface of many soils, this layer
contains organic detritus in various stages of
decomposition. Pronounced in forest soils and in
grasslands.
• A Horizon- topsoil, a mixture of organic material and
minerals.
• E Horizon-only found in some acidic soils(beneath the
O or A horizon), a zone of leaching or eluviation, Fe
and Al are and dissolved organic acids are transported
through here and deposited in the B horizon where
they accumulate.
• B Horizon-subsoil, composed of mineral
material(metals) with little organic matter. If
nutrients are present in the soil, they will be
found here.
• C Horizon- always occurring below the B
horizon, it is similar to the parent material.
This horizon contains the least weathered soil.
SOIL PROPERTIES
Physical Properties of Soil
• Texture- determined by the percentage of
sand, silt and clay (mineral particles of
different sizes).
• Porosity- how quickly soil drains, depends on
texture (Best agricultural soil is a mixture of
sand, silt and clay which allows for water
drainage and retention).Clay is useful where
contminants need to be contained and won’t
allow them to leach into groundwater.
Soil Porosity
Chemical Properties of Soil
• Clay particles are neg. charged and attract
pos. charged mineral ions that are
adsorbed(held on the surface) by the
particles. These minerals can be released and
used as nutrients by plants. This ability is
called cation exchange capacity (CEC) or
nutrient holding capacity. If a soil is more than
20% clay, its water retention is too high and
the soil is waterlogged and the roots of plants
become O2 deprived. A balance must exist.
pH of soil
• Ca, Mg, K and Na can neutralize soil acids such
as Al and H2. Therefore they are considered
bases.
• Soil acids are detrimental to plant growth
• Soil bases promote plant growth and are
essential for plant nutrition.
• Base saturation- is a measure of the
proportion of soil bases to soil acids (%).
• Soils with high CEC and high base saturation is
likely to support high productivity.
Biological Properties of Soil
• Fungi, Bacteria and Protozoans are
detritivores, which consume dead plant and
animal tissues and recycle the nutrients they
contain. Some bacteria fix nitrogen
• Rodents and Earthworms contribute to soil
mixing and breakdown of large organic
material.
• Snails and Slugs eat plant roots and some
aboveground parts of the plant.
Crustal Abundance
• The average concentration of an element in the
Earth’s crust. O2, Si, Al and Fe make up 88% of
the crust. However, the composition varies from
location to location.
• Ores are concentrated accumulations of minerals
from which economically valuable materials can
be extracted. Most ores contain metals: Cu, Ni,
Al. They are formed by a variety of processes.
• The reserve -is the known quantity of the
resource that can be economically recovered.
S.W. VIRGINIA 2003 STRIP MINING FOR
COAL
Open Pit Mining
MOUNTAIN TOP REMOVAL
Placer Mining
Subsurface mining
Types of Mining and their effects
• Environmental issues can include erosion, formation of
sinkholes, loss of biodiversity, and contamination of
soil, groundwater and surface water by chemicals from
mining processes. In some cases, additional forest
logging is done in the vicinity of mines to increase the
available room for the storage of the created debris
and soil.[28] Contamination resulting from leakage of
chemicals can also affect the health of the local
population if not properly controlled.[29] Extreme
examples of pollution from mining activities include
coal fires, which can last for years or even decades,
producing massive amounts of environmental damage.