Transcript The science of Geology - Portland State University

G201 General Geology, Winter Term 2007
instructor: Martin J. Streck
phone: 725-3379
Dept. of Geology
Concurrent G204Geology Lab is required
office: Geol 17H
email: [email protected]
office hours: T 1 - 2 pm
Lecture: T, 18:40-21:20, PCAT 160
Schedule:
Reading
Week 1: Introduction to Geology
Intrd. to Oregon Geology........................................................Chapter 1
Week 2: Plate Tectonics……………………… ……................................Chapter 2
Quiz 1: Week 3 (January 23rd)
Week 3: Minerals; mineral groups & systematics................................Chapter 3
Week 4: Weathering and Soil (Guest lecturer– Prof. Scott Burns)....Chapter 6
Week 5: Igneous Rocks............................................................................Chapter 4
.
Mid-term exam 1: Week 6 (February 13th )
Week 6: Volcanoes and igneous activity...............................................Chapter 5
Week 7: Sedimentary rocks....................................................................Chapter 7
Week 8: Metamorphism & meta. rocks, crustal deformation…… ..Chapters 8, 10
Mid-term exam 2: Week 9 (March 6th)
Week 9: Crustal deformation, Geological time.....................................Chapter 9
Week 10: Earthquakes, Earth interior, Summary of Class............Chapters 11, 12
Final exam: March 20th, 19:30-21;20
Text:
Earth, An Introduction to Physical Geology; Tarbuck & Lutgens, Prentice Hall, 8th
edition (also used in G202) – custom edition for Portland State University.
Exams:
All will be multiple-choice exams; the Final exam will include few additional
questions to be answered separately.
Readings:
See above, some selection for Week 8, 9, 10 reading will be announced in class.
Grade Allocation:
Quiz in week 3,
Mid-term exams @ 25 % each
Final written exam
Grading Policy:
93-100 A
90-92 A–
87-89 B+
83-86 B
80-82 B–
77-79 C+
73-76 C
70-72 C–
67-69 D+
63-66 D
60-62 D–
< 60 F
10%
50%
40%
The science of Geology
Geology is the science that pursues an
understanding of planet Earth
• Physical geology - examines the materials
composing Earth and the processes
generating them
• Historical geology - seeks an
understanding of the origin of Earth and
its development through time; chronology
of events
Geologic time
Accurate dates to events in Earth history
• Absolute dating
Relative dating and the geologic time scale
• Relative dating means that dates are placed in
their proper sequence or order without knowing
their age in years
The magnitude of geologic time
• Involves – millions or billions of years
• Geological processes operate
– Gradually over periods as much as millions of
years
– Episodic in events that may last only seconds
to minutes
Age in millions of years
Geologic time
scale
Early evolution of Earth
Origin of planet Earth
• Earth and the other
planets formed at the
~same time from
interstellar dust
• Nebular hypothesis
Layered structure developed
by chemical segregation early
in the formation of Earth
A view of Earth
Earth’s four spheres
• Hydrosphere
• Atmosphere
• Biosphere
• Solid Earth
Earth as a machine
Internal forces
Powered by heat from the interior
• Leads to convection in the earth
• Moves plates on the earth surface
• Produce volcanoes, earthquakes, and
mountains
External forces
- Powered by the Sun that drives external
processes in the
• Atmosphere
• Hydrosphere
• At Earth’s surface
Earth’s surface has two principal
divisions
• Continents
•Ocean basin
The workings behind the scene
Surface features, like oceans, mountains
and others, are the product of internal
workings of the earth
Earth’s internal structure
“Layercake”
Earth
• Crust
• continental
• oceanic
• Mantle
• upper
• lower
• Core
• outer
• inner
Earth’s internal structure
Mechanical Subdivision of the upper Earth
• Lithosphere
(rigid)
• Asthenosphere
(ductile, plastic)
• Mesosphere
Earth’s Surface
Earth’s crust
broken into rigid
plates
7 major plates
Where plates
meet are called
plate boundaries
Three types of
plate boundaries
Plate Boundaries
Divergent (constructive) boundary –
plates move apart, resulting in
upwelling of material from the
mantle to create crust
Convergent (destructive) boundary –
plates move towards each other;
subduction of oceanic plates or
collision of two continental plates
Transform (conservative) boundary –
plates move along each other without
either generating new lithosphere or
consuming old lithosphere
Dynamic Earth
The theory of plate tectonics
• Theory, called plate tectonics, has now
emerged that provides geologists with the
first comprehensive model of Earth’s
internal workings
The theory of plate tectonics
• Involves understanding the workings of
our dynamic planet
• Began in the early part of the twentieth
century with a proposal called continental
drift – the idea that continents moved
about the face of the planet
The Rock Cycle
The loop that
involves the
processes by
which one rock
changes to
another
Illustrates the
various processes
and paths as earth
materials change
both on the
surface and inside
the Earth
There are three rock classes
Igneous (magmatic) rocks
Sedimentary rocks
Metamorphic rocks
Igneous Rocks
Igneous rocks
Cooling + Crystallization
Lava
Magma
Melting
• formed from a magma
through crystallization
either at or beneath the
surface
• examples: lava flows,
granite, basalt, pumice
Sedimentary Rocks
Transport
Sediment
Deposition or Precipitation
Cementation + Compaction
(Lithification)
• formed through deposition of
solid particles or through
precipitation
• examples: sandstone,
claystone, limestone
Sedimentary rocks
Metamorphic Rocks
• formed through metamorphic
transformation due to heat and
pressure
• examples: schist, slate, marble
Heat + Pressure
(Metamorphism)
Compression
Heat
Metamorphic rocks
The science of Geology
Some historical notes about geology
• The nature of Earth has been a focus of
study for centuries
• Catastrophism – earth changes by large
events like floods, eruptions, etc.
• Uniformitarianism – present is key to
past; processes same through time, only
rates have changed
The nature of scientific inquiry
Science assumes the natural world is
consistent and predictable
Goal of science is to discover patterns in
nature and use the knowledge to make
predictions
Scientists collect “facts” through
observation and measurements
The nature of scientific inquiry
How or why things happen are explained
using a
• Hypothesis – a tentative (or untested)
explanation
• Theory – a well-tested and widely
accepted view that the scientific
community agrees best explains certain
observable facts
The nature of scientific inquiry
Scientific methods
• Scientific method involves gathering facts
through observations and formulation of
hypotheses and theories
There is no fixed path that scientists
follow that leads to scientific knowledge