Copyright (c) 2005 Pearson Education Canada, Inc.1-1 PowerPoint Presentation Stan Hatfield....

Copyright (c) 2005 Pearson Education Canada, Inc. 1-1

PowerPoint PresentationStan Hatfield . Southwestern Illinois College

Ken Pinzke . Southwestern Illinois College

Charles Henderson . University of Calgary

Chapter 1

An Introduction to Geology

Copyright (c) 2005 Pearson Education Canada Inc. 1-2

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



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



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



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)


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)


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


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).


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



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



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


A View of Earth

Earth is a planet that is small and self-contained

Earth’s four spheres • Hydrosphere• Atmosphere• Biosphere• Solid Earth


A View of Earth

The breathtaking beauty of Earth as seen by the Apollo astronauts in the 1960s and 1970s.


Earth as a System

Earth is a dynamic planet with many interactions among the four spheres

• Hydrosphere• Atmosphere• Biosphere• Solid Earth


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


Earth as a System

The Earth system is powered by the Sun that drives external processes in the

• Atmosphere• Hydrosphere• Earth’s Surface


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


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


The rock cycle: part of the Earth System

Rocks constantly form, change, and reform over longs spans of time.


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


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


Early Evolution of EarthOrigin 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


Earth’s Internal Structure

Earth’s internal layers can be defined by • Chemical composition• Physical properties

Layers defined by composition• Crust• Mantle• Core



Four main layers of Earth are based on physical properties and hence mechanical strength

• Lithosphere• Asthenosphere• Mesosphere (or Lower Mantle)• Inner and Outer Core



Views of the Earth’s layered structure.


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


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


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


Dynamic Earth

Mosaic of rigid plates and divergent and convergent boundaries.


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


Dynamic Earth

Mosaic of rigid plates and a transform fault boundary.


End of Chapter 1

Copyright (c) 2005 Pearson Education Canada, Inc.1-1 PowerPoint Presentation Stan Hatfield....

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