Download Dynamic Earth

Chapter 1
An Introduction to
Geology
PowerPoint Presentation
Stan Hatfield . Southwestern Illinois College
Ken Pinzke . Southwestern Illinois College
Charles Henderson . University of Calgary
Copyright (c) 2005 Pearson Education Canada, Inc.
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The Science of Geology
Geology is the science that pursues an
understanding of planet Earth
• Physical geology - examines the materials
composing Earth and seeks to understand
the many processes that operate beneath
and upon its surface
• Historical geology - seeks an
understanding of the origin of Earth and
its development through time
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The Science of Geology
Geology, people, and the environment
• There are many important relationships
between people and the natural
environment
• Some of the problems and issues
addressed by geology involve natural
hazards, resources, world population
growth, and environmental issues
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The Science of Geology
A Canadian Profile
• Sir William Edmond Logan
has been called Canada’s #1
scientist in history
• He was the first director of
the GSC and was active in the
outdoor pursuits of geology
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The Science of Geology
Some historical notes about geology
• The nature of Earth has been a focus of
study for centuries
• Catastrophism: shaping of the Earth’s
landscape by catastrophes
• Uniformitarianism: a principle first
proposed by James Hutton that
represented the Birth of Modern Geology
(processes that operated in the past also
operate today)
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Geologic Time
Geologists are now able to assign fairly
accurate dates to events in Earth history
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 (apply Principles of
Superposition and Fossil Succession)
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Geologic Time
The magnitude of geologic time
• Involves vast times – millions or billions of
years (the Earth is 4.5 Billion years old!)
• An appreciation for the magnitude of
geologic time is important because many
processes are very gradual
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Geologic Time
The Geologic Time Scale. The
numbers are absolute ages in
millions of years before present.
Note that the Precambrian
accounts for 88% of geologic
time and yet the Phanerozoic with
its wealth of fossils includes many
divisions (Eras, Periods, Epochs).
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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
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The Nature of Scientific Inquiry
How or why things happen is 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
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The Nature of Scientific Inquiry
Scientific Methods
• Scientific method involves gathering facts
through observations and creative
formulation of hypotheses and theories
There is no fixed path that scientists
follow that leads to scientific knowledge
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A View of Earth
Earth is a planet that is small and selfcontained
Earth’s four spheres
• Hydrosphere
• Atmosphere
• Biosphere
• Solid Earth
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A View of Earth
The breathtaking beauty of Earth as seen by the Apollo astronauts in the
1960s and 1970s.
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Earth as a System
Earth is a dynamic planet with many
interactions among the four spheres
• Hydrosphere
• Atmosphere
• Biosphere
• Solid Earth
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Earth as a System
Parts of the Earth system are linked
Characterized by processes that
• Vary on spatial scales from fractions of a
millimetre to thousands of kilometres
• Have time scales that range from
milliseconds to billions of years
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Earth as a System
The Earth system is powered by the Sun
that drives external processes in the
• Atmosphere
• Hydrosphere
• Earth’s Surface
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Earth as a System
The Earth system is also powered by the
Earth’s interior
• Heat remaining from the formation and
heat that is continuously generated by
radioactive decay power the internal
processes that produce volcanoes,
earthquakes, and mountains
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The rock cycle: part of the Earth System
The loop that involves the processes by
which one rock type changes to another
Illustrates the various processes and paths
as earth materials change both on the
surface and inside the Earth
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The rock cycle: part of the Earth System
Rocks constantly form, change, and reform over longs spans of time.
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The Face of Earth
Earth’s surface has two principal divisions
• Continents
• Ocean Basins
• Significant difference between the continents and
ocean basins is their relative levels
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The Face of Earth
Continents
• Most prominent features are linear
mountain belts
• Shields
Ocean Basins
• Ocean ridge system – the most prominent
topographic feature on Earth
• Deep-ocean trenches
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Early Evolution of Earth
Origin of Planet Earth
• Most researchers believe that Earth and
the other planets formed at essentially the
same time from the same primordial
material as the Sun
• Nebular hypothesis
Layered structure developed by chemical
segregation early in the formation of
Earth
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Earth’s Internal Structure
Earth’s internal layers can be defined by
• Chemical composition
• Physical properties
Layers defined by composition
• Crust
• Mantle
• Core
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Earth’s Internal Structure
Four main layers of Earth are based on
physical properties and hence mechanical
strength
• Lithosphere
• Asthenosphere
• Mesosphere (or Lower Mantle)
• Inner and Outer Core
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Earth’s Internal Structure
Views of the Earth’s layered structure.
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Dynamic Earth
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
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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
Plate Boundaries
• All major interactions among individual
plates occur along their boundaries
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Dynamic Earth
Plate Boundaries
• Divergent boundary – two plates move
apart, resulting in upwelling of material
from the mantle to create new seafloor
• Convergent boundary – two plates move
together with subduction of oceanic plates
or collision of two continental plates
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Dynamic Earth
Mosaic of rigid plates and divergent and convergent boundaries.
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Dynamic Earth
Plate Boundaries
• Transform fault boundaries - located
where plates grind past each other
without either generating new lithosphere
or consuming old lithosphere
• Changing boundaries - new plate
boundaries are created in response to
changes in the forces acting on the
lithosphere
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Dynamic Earth
Mosaic of rigid plates and a transform fault boundary.
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End of
Chapter 1
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