EESA06 Textbook Notes.docx

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27 Apr 2012
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EESA06 Textbook Notes
Chapter 1: Introduction to Physical Geology and the Environment
What is Geology?
Geology the study of earth
Moving Continents
1.1 William Smith Father of English Geology, first to publish a geological map
1.2 William Logan first to systematically describe the geology of Canada (Candian)
- Cross-section a hypothetical vertical slice thru the land
1.3 Alfred Wegener theory of continental drift in 1912 “The Origin of Continents and Oceans”
- Pangea continents has previously been clustered together in a large land mass
1.4 J. Tuzo Wilson plate tectonics theory in the early 1970s (Canadian)
- Transform faults large-scale faults that offset the crust laterally but neither created nor destroyed
material, now recognized as a major plate boundary type
- Hot spots active volcanoes, young volcanic islands stuck in the middle of the oceans
- Volcanic islands chains (ex: Hawaiian Islands) resulted from a moving plate drifting over a
stationary magma plume in the mantle support for plate tectonic theory
Time and Geology
Deep time vastly greater amounts of time (more than hours, years)
Mid-ocean ridge a giant mountain range that lies under the ocean
Earth is estimated to be at least 4.55 Ga years old
What do Geoscientists Do?
1.5 Exploration Geologists looking for gold, diamonds and other metals
Geoscientists expand the scope and responsibilities of modern geologist into additional scientific fields
Geochemists working in a ordered environment of the laboratory and use high-technology equipment to
analyze the chemistry of rocks or minerals
Mineralogists study minerals
1.6 Petrologists study the makeup of rocks and how they form
Geophysicists using high-tech equipment in the field, using boats, planes, or satellites to learn more of
the nature of the physical conditions on or under the Earth‟s surface
Petroleum/coal geologists search for oil and gas and coal
Seismologists study how to measure and mitigate earthquake activity
Paleontologist studies the fossilized remains of ancient organisms
Glacial Geologists study landforms and sediments left behind by ice sheets (glaciers)
Hydro-geologists study and protect sediments that contain and transmit water
1.7 Environmental Geoscientists finding and managing drinking water, dealing with a wide range of
wastes ranging from radioactive waste to household (municipal) waste
1.8 Engineering Geologists work with the challenges of engineering structures that form part of the
human landscape, landscape stability problems.
1.9 Geomatician collect, organize, analyze and create images from any spatial and geographical data
available in digital form
What is the Scientific Method?
Scientific Method the process by which scientists first identify a problem, then they select a
methodology to collect data in order to help solve the problem, then they analyze and interpret the
information, and come up with a hypothesis, after several test, form a theory
Hypothesis a theoretical explanation where the geologist
How did the Earth form?
- Nebula a cloud of gas and dust particles
- Bulbous core & flattened disc created by gas and dust rotate and contract
- Sun created from a nuclear fusion
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- Planets - dust in the outer disc condensed to form rocks and metals that combined to form large
rounded planets
- Planetismals much smaller, irregularly shaped planets
- Accretion the process of building large bodies of matter thru collisions and gravitational attraction
- Terrestrial planets (ex: Mercury, Venus, Earth, Mars) form close to the sun, small, dense, rocky
- Jovian planets (ex: Jupiter, Saturn, Uranus and Neptune low density, large, further from sun
What was the early earth like?
Differentiation process of zonation of different materials within a planet
- Heavier metals (iron and nickel) settle towards the center, lighter metals (silica and oxygen) rise
towards Earth‟s surface
1.10 Meteorites small solid particles of rock, metal, and or ice/orbiting the Sun
1) iron (rare but look unique easily found) iron mixed with small amount of nickel
2) stony-iron iron-nickel alloy and silicate minerals in about equal parts
3) stony meteorites (most common, look like earth‟s rocks) silicate minerals (plagioclase, olivine,
pyroxene) and may contain small amount of iron-nickel alloy
90% are Chondrites contain round silicate grains aka chondrules
10% are Achondrites lack chondrules
Carbonaceous chondrites composed mostly of serpentine or pyroxene and contain up to 5%
organic materials, believed to have same composition as the original material from which the
solar system was formed
Achondrites similar to terrestrial rocks in composition (basalt) and texture (igneous rocks)
Internal Structure of the earth
- Core composed of iron alloy (iron + nickel +silicon)
- Mantle composed of Fe-Mg silicates (form a rock called peridotite)
- Outer crust composed of lighter rocks such as basalt and granite
Basalt a fine-grained, mafic, igneous rock composed predominantly of ferromagnesian minerals
and with lesser amounts of calcium rich plagioclase feldspar
- Lithosphere plates large pieces of crust and uppermost rigid mantle broken from mantle
convection
- Asthenosphere the weak layer, more mobile
Formation of the Early Atmosphere
- Outgassing water and gaseous elements released during volcanic eruptions
Early Life Forms
- Prokaryotes microorganisms, earliest life forms preserved in the geological record
- Stromatolites organic structures grown by prokaryotes by trapping sediments
What is the “Earth System”?
Earth System a small part of the larger solar system but also has its own component parts or
subsystems (aka spheres) - include atmosphere (gases), hydrosphere (water) , biosphere(living) and
geosphere (rock or other inorganic Earth materials)
- External energy source sun, drives atmosphere and hydrosphere
- Internal energy source geothermal heat, radioactive decay of minerals with Earth, drives plate
movement, volcanic eruptions, and earthquakes
Rock cycle conceptual model that links rock-forming process that operate in Earth‟s crust
- Magma molten rock
- Igneous when magma solidifies
- Sedimentary unconsolidated sediment becomes lithified (cemented/consolidated into rock)
- Metamorphic - subjected to heat and pressure, if high enough temperature rock melts to become
magma completing the cycle
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Chapter 2: Plate Tectonics
What is Plate Tectonics?
- Plate Tectonics Earth‟s surface is divided into a few large, thick plates that move slowly and
change in size
- Continental Drift continents move freely over the Earth‟s surface, changing positions relative to
one another
- Sea-floor spreading hypothesis that the sea floor forms at the crest of mid-oceanic ridges, then
moves horizontally away from the ridge crest toward and oceanic trench, two sides of the ridge are
moving in opposite directions like slow conveyer belts
How did the plate tectonics theory Evolve?
The Early Case for Continental Drift:
- Paleoclimatology the study of ancient climates
Wegener studied climates, rocks and fossil, magnetic poles supported the continental drift
Renewed Interest in Continental Drift
Study of the Sea Floor
- Multibeam sonar measures water depth and draws profiles of submarine topography
- Sidescan sonar measures the intensity of sound reflected from the ocean floor and provides
detailed images and information about sediments and bedforms on the sea floor
- sub-bottom profilers - examine the strata (layers) beneath the floor of the lake/ocean
- seismic reflection profiler louder noise, lower frequency, reflects from layers within sediment and
rock, records water depth and reveals internal structure of sea floor (Ex: faults, folds)
- Rock dredge an open steel container dragged over the ocean bottom
- Rock corer steel pipe dropped vertically into mud and sand of ocean floor
- Sea-floor drilling drilling derrick
- Submersibles small research submarines, observe, photograph and sample rock and sediment
Geophysical Research
- Polar wandering an apparent movement of the Earth‟s plates
Recent Evidence for Continental Drift
- Rocks in Brazil and African country Gabon are very similar
- GPS allows us to watch continents move in real time
2.1 Measuring Plate Movement in Real Time
- Space geodesy a space-based technique for taking very precise measurements of points on the
earth‟s surface (ex: very-long-baseline interferometry (VLBI), satellite laser ranging (SLR), GPS)
- GPS is the most useful technique for studying earth‟s movements
What is Sea-Floor Spreading?
Wegener thought ocean floors remained stationary as continents moved
Harry Hess 1962 at Princeton suggest that sea floor might be moving too
- Spreading axis (spreading center) the ridge crest (MOR) with the sea floor moving away from it
on either side
- Subduction the sliding of the sea floor beneath a continent or island arc
- Convection a very slow circulation of a substance driven by differences in temperature and
density within that substance
How Old is the Sea Floor?
- Fairly young only 200 million years old
What are plates and how do they move?
- Plate a large, mobile slab of rock making up part of the Earth‟s surface
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