The Science ofThe Science of HISTORICAL GEOLOGY HISTORICAL GEOLOGY““If your mind is empty, it is always ready for anything; If your mind is empty, it is always ready for anything;

it is open to everything.”it is open to everything.” Zen Proverb Zen Proverb

The Science of GeologyThe 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.

• It’s high adventure.

• It reveals the path of events that put us here.

• It shows us where we are headed….

Why Study the Why Study the History of the Earth?History of the Earth?

• It explains how our world functions.

Why Study the History Why Study the History of the Earth?of the Earth?

• Humans and the natural environment are interrelated and interdependent. – Evolution– Natural Hazards – Resources – Energy, Water,

Agriculture, etc.– Environmental Issues

• Humanity’s own survival depends on understanding how to live in harmony with the “laws” governing our physical/biological world.

Humans ask questions to Humans ask questions to understand the natural environmentunderstand the natural environment

• How did the Universe and our Solar System form?• How did the Earth form? How do rocks form?• What is Plate Tectonics?• How old is the Earth?• How did life on Earth begin? • How has life on Earth changed through time?• How has the Earth changed through time? • Why do earthquakes and volcanic eruptions occur? • What governs the location of mountain ranges?• Why did mass extinctions occur? • What caused the ice ages? • What causes global warming?

Curiosity Leads to Exploration

The Answers are Written in The Answers are Written in the Rocksthe Rocks

Rocks and Fossils are important tools for geologists that tell a story of what Earth

like in the past.

• Life Forms (flora and fauna)

• Plate Tectonics

• Mountain Building

• Volcanic Eruptions

• Age Dating

• Paleoclimate

• Extinctions

• Global Sea Level Rise and Fall

• Ice Ages

Rocks preserve records of more distant times, when the animals on this planet were strange...

…bizarre…

…alien?

Hallucigenia, Wonderful Life

Some rocks are older than animal life.

They record events that shaped the world on which we live, and they tell of huge events over grand lengths of time.

Some rocks even date back to the youngest days of the planet…

…4,567,000,000 years ago.

How do geologists read the story recorded in the rock and fossil record?

Its surface never rests. Change is constant and continuous.

Some changes are visible at the surface, caused by wind, weather, wave action, even gravity.

Today, Earth is a vital, dynamic planet.

These changes occur on the same time-scale as humanactivity,allowingus to watchthem occur.

But thereare longerprocessesat work too.

Over many human lifetimes, water and wind have removed most of this layer of rock to create this arch.

The rock itself was made in a desert that is now long gone.

The link between past, present, and future occurs because the processes at work on the surface of the Earth have been at work there since the beginning.

In shaping the surface of the planet, they have left a record for us to read, in rocks and fossils.

The surface changes constantly,but the processes remain the same.

The past is the key

to the present…

…and the future

Science operates through the Science operates through the use of the use of the Scientific MethodScientific Method

““A poverty of ideas is a more serious deficiency than A poverty of ideas is a more serious deficiency than faulty reasoning”faulty reasoning” Robert MagnanRobert Magnan

• Observe• Raise Question• Form Hypothesis • Test Hypothesis• Gather Data• Modify Hypothesis• Retest Hypothesis

Limits of ScienceLimits of Science

• Questions (hypotheses) must be testable. • Results must be repeatable.• No moral or aesthetic judgments.• Can only test the natural, physical world.

Scientific discoveries may be controversial… especially when they are first made.

What is a Hypothesis? What is a Hypothesis? What is a Theory?What is a Theory?

Confusion Over TerminologyConfusion Over Terminology• Terms that mean one thing to scientists and

something very different to the lay person. • Based on research that helped scientists write major U.S. and international climate reports.

What the public thinks

A place plants grow

Spray can

Result of doing something well

Speculation; a hunch

A good-looking person who markets clothing

The ozone hole

Term

“Greenhouse”

“Aerosol”

“Positive Feedback”

“Theory”

“Model”

“Ozone”

What scientists mean

The warming effect created by heat-trapping gases

Tiny particles

A vicious cycle

An established understanding of how something works

A computer simulation

A heat-trapping gas

What is a Hypothesis?What is a Hypothesis?

• Hypothesis – A tentative (or untested) explanation.

• A hypothesis that survives repeated testing and challenges, and is supported by a large body of evidence, may be elevated to the status of a Theory.

What is a Theory?What is a Theory?• It is important to understand that the term “theory” has very different

meanings to scientists and to the general public.

• In Science, a theory…– Is not just a wild idea, a guess, or a belief. – Is not an untested hypothesis– Is also not “merely” a fact; it is actually a collection of hundreds of thousands of

facts and direct observations, assembled in order to coherently explain the functions and processes in part of our universe.

– Theories have survived close examination, and can be accepted with confidence.

– A theory represents knowledge that has very high probability of being correct.

– A theory remains open to tests and revision….that can make theories stronger/weaker.

• Whereas, in common language, – “Theory” implies a lack of knowledge or a guess, conjecture, opinion,

speculation. In this usage, a theory is not necessarily based on facts.

What is a Theory?What is a Theory?• Theory – A well-tested and widely-accepted explanation

of natural phenomenon that the scientific community agrees best explains certain observable facts.

Examples of Theories:• The Theory of Universal Gravitation

– The concept that mass attracts mass; the foundation of physics • Atomic Theory

– The construction of atoms from protons, electrons, and neutrons, the foundation of chemistry

• Special Theory of Relativity – Einstein’s contribution to quantum mechanics and the foundation of astronomy

• Cell Theory – The concept that cells are the basic unit of structure in every living thing

• Plate Tectonics Theory – The Earth's outer layer is made up of plates, which have moved throughout Earth's

history; the foundation of modern geology • Evolutionary Theory

– The change in the inherited traits of a population of organisms through successive generations; the cornerstone of modern biology

What is Scientific Law?What is Scientific Law?

• Paradigm – A theory may become a paradigm (a predominant worldview in the realm of human thought) or

• Scientific Law after further testing and acceptance.

• Example: The Theory of Universal Gravitation or “The Law of Gravity”

Peer-Reviewed Journals – Peer-Reviewed Journals – Primary LiteraturePrimary Literature

Science Science MagazinesMagazines

Secondary LiteratureSecondary Literature

Summary of Scientific MethodSummary of Scientific Method

1. Make observations:• The shape of Earth’s continents appear to fit

together like pieces of a jigsaw puzzle.

2. Identify a question or problem:• At some time in the past, were the continents

joined together forming one large land mass?

3. Develop working hypothesis (idea to explain the observations):• During Earth's history, the continents were joined

together into one giant supercontinent (called Pangaea meaning "All Lands" in Greek).

Summary of Scientific MethodSummary of Scientific Method4. Determine ways to test the hypothesis by

experimenting and either accept, reject, or modify the hypothesis:

• Develop tests that support or disprove that the continents were once joined.

• Develop tests that support or disprove that the continents have moved (and may still be in motion).

• The simplest explanation is typically the best.• What is some of the information we can use to do this?

• Fit of Continents• Rock Types• Rock Structures• Fossils• Paleoclimate Data • Apparent Wandering of the Earth's Polar Regions• Geodetic evidence that continents are moving at a

measurable rate

Summary of Scientific MethodSummary of Scientific Method5. Collect Data6. Analyze Data:

• Try to piece continents back together based on data collected

7. Interpret Data:• Are there trends or correlations?

8. Support or refute hypothesis and develop new hypothesis, if appropriate.

9. Repeat Steps 4 thru 10.10. Only after repeated testing of the hypothesis, in

which it gains considerable experimental or observational support, is it accepted and a theory is established.

11. A theory ultimately may become a paradigm or scientific law.

Newsweek, July 2 thru 9, 2007