Download PHSC 4013 Course Outline—Fall 2008

PHSC 4013 Course Outline—Fall 2008
Introduction
What is Earth Science?
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Earth Science = Any of the sciences (geology, meteorology, oceanography,
astronomy) that deals with the Earth or one of its parts
Physical Science = Any of the natural sciences (physics, chemistry, astronomy,
paleontology) that deal with non-living materials
Science = knowledge or system of knowledge that covers general truths of the
operation of general laws, especially as tasked and obtained through the Scientific
Method.
Each of the sciences we will look at to study the Earth system has its foundation in
Physics, “the science behind all the sciences”
These sciences are not distinct and compartmentalized, but rather they are
overlapping, interrelated, and interacting
The Scientific Method, Natural Systems, and Environments
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We use a paradigm developed over the past 2,500 years to investigate our
surroundings: the Scientific Method
The Scientific Method is a systematic approach to explore the innermost workings
of the universe and it contains several well-defined steps:
o A Hypothesis is formulated, which is an educated guess about how
something works.
o The hypothesis is tested through experimentation, observation, and
simulation to check for consistency: do the actual results match the
expected results in a reasonable manner?
o If the hypothesis passes the tests over time, it is upgraded to a theory,
which continues to be tested as our realm of knowledge continues to grow.
o A Scientific Law is a description or truth about how something works, and it
usually can be expressed in a concise, simple formula
A System = a group of interacting parts to form a complex whole
The environment = everything that surrounds and influences an organism
Positive Feedback = mechanisms within a system that tend to enhance change;
Negative Feedback = mechanisms within a system that tend to resist change and
stabilizes the system
Two energy sources provide energy for the Earth System: external (the Sun),
which powers the ocean currents, heats the surface and atmosphere, and powers
the weather; and internal (the heat from the interior of the Earth), which drives
plate tectonics, earthquakes and volcanoes.
An example of a set of laws that we experience in the daily realm are Newton’s
Laws of motion
o An object at rest or in motion will remain at rest or in motion unless acted on
by an outside influence
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o F = ma, that is, the force exerted by an object of mass m is proportional to
its acceleration, a.
o Every action has an equal and opposite reaction.
One additional law from Newton includes the law of universal gravitation, which
states that gravity is proportional to the product of the two masses between which
gravity acts, but inversely proportional to the square of the distance between these
two objects. In summary, gravity is the same everywhere in the Universe.
Geology: the Building Materials of Earth and How Earth’s Surface is
Sculpted
The Building Materials of Earth
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Rocks versus Minerals
o Mineral = Any naturally occurring inorganic solid that possess an orderly
internal structure and a definite chemical composition.
o Rock = any solid mass of mineral or mineral-like matter that occurs naturally
as part of the planet.
o These are materials found on the surface of the Earth, but as one goes
deeper, the mean density of these properties increases
A brief overview of the internal structure of the Earth
o A thin crust, 5 – 70km thick , makes up the outermost part of the Earth
o The Lithosphere, or sphere of rock, includes the crust and the outermost
core; the asthenosphere, or “weak sphere” includes the upper mantle and
consists of weak rock that is able to slowly flow in response to the uneven
distribution of heat from deep within the Earth.
o The Mantle, 2900km thick, makes up the next layer.
o The core, mostly of the metals iron and nickel, is divided into two parts: the
outer core (2270km thick) and the inner core (1216km in radius). The outer
core is liquid, but the inner is solid due to the tremendous pressures
overlaying the inner core.
All material is made up of atoms
o An Atom consists of a small, dense nucleus of protons and neutrons, which
is surrounded by clouds of electrons
o The number of protons defines what element the atom makes, this also
defines the atomic number of the element
o The number of electrons in an atom equals the number of protons, if the
atom is neutral: electrons have negative charge, protons have positive
charge (equal to that of the electron), but protons are nearly two thousand
times more massive than electrons
o Isotopes are variants of the same element but different in mass number
(neutrons + protons). Some isotopes are unstable and come apart, or
decay, naturally in a process known as radioactive decay.
o The Periodic Table is used to classify the different elements according to
their properties
Properties of minerals used to classify them include: luster, crystal form, color,
streak, hardness, cleavage, fracture, and specific gravity (related to density).
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The silicates are the most common mineral group; they all have as their
fundamental building block the silicon-oxygen tetrahedron.
The Rock Cycle gives rise to three main types of rocks, based on their origins or
means of formation
o Igneous rocks originate from cooling and crystallization of magma from
inside the Earth: Extrusive or volcanic igneous rocks form when magma is
forced to the surface; Intrusive or plutonic igneous rocks are formed when
magma cools inside the earth.
o Sedimentary rocks result from the compaction and cementation of
sediments formed on the surface by weathering, erosion, and deposition
processes.
o Metamorphic rocks are formed when pre-existing rock is altered or
metamorphized by extreme heat, pressure, and chemically active fluids.
Rocks are classified by their texture and mineral composition; the rate of cooling of
igneous rocks determines the size of the crystals that make up the rock (fast
cooling means tiny crystals, slow cooling means larger crystals).
Some of the most important accumulations of metallic mineral resources are
produced by igneous and metamorphic processes.
Shaping Earth’s Surface
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External processes occur that sculpt the face of the earth and include:
weathering—the wearing away of rock near the surface, mass wasting—the
transfer of rock material downslope by gravity, and erosion—the removal and
transport of material by a mobile agent such as wind, water, or ice. These
processes ultimately get their energy from the Sun
Internal processes also occur to shape the face of the earth: volcanism and
mountain building get their energy from Earth’s interior heat
Differential weathering can occur depending on key variables that can affect its
rate: climate, heat, and moisture patterns; chemical composition of the rock; and
the degree of jointing and fracturing that occurs in the rock.
Mass wasting may be rapid or it may be gradual, and it may involve wet or dry
materials. The following are factors that influence changes in gravitational stresses
on the materials: water saturation of slopes, oversteepening by erosion or human
activities, earthquakes, or vegetation removal.
The texture of the soil depends on the amount of sand-, silt-, and clay-sized
particles that make up the soil; this makeup is key in determining the agricultural
potential, flooding potential, and engineering characterisitics.
Moving water does its work at modifying the landscape and maintaining the water
cycle through:
o Streams that produce v-shaped valleys in the landscape and transport
sediment. This sediment gets deposited in an area known as the stream or
river mouth
o Floods occur from time to time and are part of the river system
o Glaciers are masses of compressed ice that moves by internal plastic flow
and by basal slippage. They remove large rocky blocks by ice action and
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scour the surface rock by abrasion; they lead to u-shaped valleys and
dramatic landforms
Deserts are arid regions where evaporation exceeds the supply of water from
precipitation; weathering rates are generally lower than in humid regions but
flowing water does do considerable erosional work (e.g. the Grand Canyon) as
does wind.
(Note: we will not focus on Chapters 5 and 6—the reading of these chapters is
optional, and Chapter 4 we will focus mainly on the areas of erosion…that is we
will not do the entire chapter. The exception of this is what is talked about in class)