ENVIROMENTAL SCIENCE – Term 3 notes
Need to look at diagrams in course notes when reading through these notes.
Geology
The nature of geology:
Geologic processes:
1. reshape the earth’s interior and surface
2. determine distribution of metal and petroleum (important)
3. control places susceptible to volcanoes, floods and other natural disaster
inhabited areas.
It is the study of ancient sea, rivers, other environments, organisms that inhabited
these environments, formation and destruction of mountain ranges.
How geology affects our everyday lives:
Geologic resource dependence:
- Most important geologic resource = energy.
- Petroleum gave rise to the development of the internal combustion engine ( engine
which generates motive power by the burning of petrol, oil, or other fuel with air
inside the engine)
- Advances in agricultural techniques = increased supply of food and raw material.
- Essential for economic and population growth which both 100% depend on
affordable energy.
Economics and politics:
- Geology controls distribution of energy sources to build houses, cars, factories etc.
- Resources are not evenly distributed so no country is self-efficient.
- Leads to wars to secure these resources.
This distribution of natural resources:
- Resources are distributed in different ways and in uneven amounts around the
world. i.e. geologic processes of the past (volcanic activity, tectonic movement)
results in various quantities of certain resources only available at specific locations.
Sustainable building sites:
- Some areas = sustainable building sites.
- Other areas = underlain by unstable geologic materials that will cause damage.
Natural hazards:
- Constrain where people can live i.e. earthquakes, floods etc.
, History of geology:
Catastrophism: the theory that the earth’s features (mountains, valleys, oceans,
rivers) were permanent and had been produced by a few great upheavals.
Uniformitarianism: this is the counter hypothesis of catastrophism. James Hutton,
the father of scientific geology, assembled this. The principle of uniformitarianism is
the same process we observe today and has been operating throughout earths
history. The species adapt or go extinct when these landforms change.
Geologic time:
Relative dating: before geology emerged, scientists recognised that a pile of rock
layers record a sequence of past events. Layers at bottom = oldest, layers on top =
youngest. The pile records a relative sequence of events, not a numerical measure in
years. This is known as relative dating.
Radiometric methods: a method introduced, in comparison to relative dating, which
determined the precise age of rocks.
Scientific method in geology:
Includes the following steps:
i) observe and measure
ii) form a hypothesis (a plausible but unproven explanation for the way something happens)
iii) test the hypothesis
iv) formulate a theory
v) formulate a law or principle after testing the theory.
Earth as a system:
a) A system: any size group of interacting parts that form a complex whole.
b) Open system: both energy and matter flow into and out of the system e.g. the ocean.
c) Closed system: is self-contained, allows only energy to flow into and out of the system
e.g. the Earth as whole
Earth = a closed system with many interacting subsystems that involve the transfer of
energy and materials from area, and state, to another. Recourses all exist within earths
system and geologists study how these resources are created, altered and move from place
to place.
,Humans alter many of the transfer processes and at the same time alter the amounts of
recourses in storage. Matter cannot be destroyed or created, but it can be altered from an
un-usable state to a usable one and vice versa.
Earths spheres:
Hydrosphere: all of earths water, including oceans, lakes, streams, underground
water, snow and ice. Does not include water vapour in the atmosphere.
Geosphere: solid earth from core to surface, composed of rock and unconsolidated
sediment (A sediment that is loosely arranged or unstratified)
Atmosphere: the mixture of gases that surrounds earth = nitrogen, oxygen, carbon,
argon, carbon dioxide, water vapour.
Biosphere: all of earth organisms + organic matter not yet decomposed.
The formation of rocks:
What is a rock?
A coherent, naturally occurring solid, consisting of an aggregate of minerals.
Coherent: rock holds together, must be broken to separate into pieces.
Naturally occurring: manufactured materials like concrete and brick do not qualify.
Aggregate of minerals: aggregate of many minerals grains or crystals, stuck or grown
together.
What holds rock together?
Natural cement: mineral material that precipitates from water and fills the space between
grains. Clastic rocks are rocks whose grains are stuck together by cement.
Crystalline rocks: rocks whose crystals interlock with one another (fig. 1.5)
The basis of rock classification:
Rocks can best be described on the basis of how they are form.
Igneous rocks: form by the solidification of molten rock.
Sedimentary rocks: form either by the cementing together of fragments (grains) of broken
pre-existing rocks or by the precipitation of mineral crystals out of water solutions.
Metamorphic rocks: form when pre-existing rocks change into new rocks in response to a
change in pressure and temperature.
, Each of the three groups contains different individual rock types, distinguished by physical
characteristics.
i) grain size: individual grains in a rock can be measured by mm or cm. some rocks = grains
same size vs. different sizes.
ii) composition: proportion of chemicals and assemblage of minerals.
iii) texture: arrangement of grains in rock.
iv) layering: bands of different compositions of textures or alignment of infrequent grains so
they trend parallel to one another. Layering in sedimentary rocks = bedding, layering in
metamorphic rocks = foliation.
The rock cycle:
The progressive transformation of earth materials from one rock type to another
which can follow many paths around the cycle
e.g. 1: igneous rock may weather and erode to produce sediment which forms
sedimentary rocks. The new sedimentary rocks get buried. Change in pressure +
temp = sedimentary rocks develop into metamorphic rocks, which could then
partially melt to create magma.
Igneous sedimentary metamorphic igneous
e.g. 2: Metamorphic rocks are uplifted + eroded to form new sediment and then new
sedimentary rock.
Igneous sedimentary metamorphic
e.g. 3: igneous rock metamorphosed directly without first turning into sediment.
Metamorphic rock could again be turned into sedimentary rock.
Igneous sedimentary metamorphic
Plate Tectonics:
Alfred Wagner said that the distribution of continents and oceans basins that we
have today evolved from one supercontinent known as Pangea.
Continental drift theory: earths continents move relative to eachother by drifting across the
ocean bed.
Sea-floor spreading: continents drift apart because new ocean floor forms between them
(as a process).
Subduction: continents move towards eachother because old ocean floor sinks back down
into the earth’s interior.
