Introduction to the study of the earth



Anyone who has traveled at all realizes that not all parts of the earth are the same

Both surface features and the rocks below the surface

It's also clear that the earth is not ever-present and unchanging

Lots of examples of small (and large) scale changes we can observe

Multnomah Falls rockfall

Yosemite Valley: Glacier Point rockfall, Merced River 1997 floods

Applegate River at Hwy. 199

There are 2 processes: Construction and Destruction

These examples are all destructive

Happen at a faster rate so we recognize them

The constructive processes are also exciting

Volcanoes, earthquakes

They also seem to happen fast, but...

More on this later

Geology is the study of these surface and bedrock processes

What makes our earth

We tear it down in The Hydrosphere

Geologists need to be able to see the actual rocks

We're not all soil scientists!

Unfortunately, there's a lot of dirt! (Not to mention placed covered by water)

Look for places where the rock is exposed at the surface

Outcrops: Let's hear it for road cuts!

DIGRESS TO: bedrock vs. float

In any event, need to get all the dirt and biological contamination out of the way in order to adequately do our job

Not everyone gives geology much respect

Geology isn't a 'Fundamental Science'

Not like Physics, Chemistry, etc.

How many of you are here because of this?

We can't answer all of our questions by doing empirical experiments

Geology is a 'Multidisciplinary' science

This is a $.50 word which says that it draws strength from many different areas of scientific study

DIGRESS TO: don't freak out; just take big words apart

Geophysics, geochemistry, etc. (and math? I'll try to minimize the pain.)

Geology is also a field oriented science

The field IS our science!

Hope to have several field trips during the term

DIGRESS TO: who will be invited along

Possibility of top students joining my RCC trips

Earth has been here a long time

The study of geology gives us our only glimpse into the earth's past

This glimpse is admittedly biased, as we will come to learn throughout this course


Geology and the Law

I'm a real geologist

I love geology and being a geologist

The study of the earth is the best there is

And the job requirements aren't that tough (obviously)

What we do is pretty straight forward

Observe and record; and beat up rocks

It is traditional that geologists...

Camp out a lot and spend lots of time around a campfire

Have a realistic view of time and space, and are extremely well-adjusted

Are relatively unaffected by much of the normal day-to-day BS

And best of all, there are no real "laws" in geology

Not like the fundamental sciences which rely on 'natural laws' to help them make sense

And keep them boring and predictable

All we have are a few general guidelines to help clarify the mess

Some of our best follow...

Uniformitarianism - 'the present is the key to the past'

If a process is active today, it probably worked the same across geologic time

Gravity, water running downhill, that kind of thing

The concept of uniformitarianism states that there are natural laws that have worked continuously and unchangingly throughout geologic time

Careful here...

'Change' is the rule in geology (as it is in life)

I like to think that a strict uniformitarian view may be too restrictive

You'll find that I preach skepticism in this course

A geologic idea is much like a weather forecast - both are based of estimates of probability

A good geologist is rarely 100% sure

Beware modifiers such as: always, never, all, every, forever

All in all, though, uniformitarianism is a valid and needed concept

Law of Superposition

" any undisturbed sequence of layered rock any one layer will be older than the layer above it and younger than the layer below it"

The key term here is "undisturbed sequence of layered rock"

Commonly used to determine the relative ages of sedimentary rocks

Law of Original Horizontality

States that sedimentary beds are laid down horizontally (or near horizontally)

If they aren't flat, some tectonic force must have disturbed them

Define "tectonics"

There are definitely exceptions to this "law"

DIGRESS TO : regional vs. local

With rules like these to follow you can see that geologists have to use their imaginations

There are others which we will discuss at other times

Law of Cross-cutting Relationships

And the heavyweights!

Strickler's Laws of GeoFantasy


Geology and the Scientific Method

Scientific experimentation is somewhat different between geology and the fundamental sciences

In physics and chemistry, the scientific method can be applied

Hypotheses and experimentation to prove (or disprove) the hypothesis

My version of the S.M. may be a bit different, and include a couple additional steps

Wild & Crazy Idea ---> Hypothesis ---> Theory ---> Law ---> Dogma ---> Stagnation

Click here for a more detailed discussion of my version of the scientific method

In geology, we really can't PROVE anything

No Universal Laws of Geology to form a firm foundation for experimentation

The complexity of the lab!

Also, many of the processes occur outside of our range of vision

Both spatial and temporal (space and time)

EXAMPLE: high grade metamorphics

SHOW: sedimentary --> migmatite samples

There is no black and white in geology - only infinite shades of grey

Nothing works in every possible situation (oops, there are those modifiers!)

Laboratory experiments are commonly inadequate in their attempts to duplicate natural processes

The earth is the most complex and well-equipped lab we know of

Impossible to duplicate in an artificial and controlled setting

So what do we really know for sure?

You need to keep an open mind when trying to study the earth

Helps to have several ideas going at the same time

Work to "rule out" as well as "prove"

And keep updating your "forecast!"

In geology, you can ask one question and get three more as an answer

Sometimes it doesn't seem fair

Put it all together and it seem pretty hopeless

Doesn't mean that we can kiss off the study of the earth

Geologists are trained to observe & record what they see in the natural world

These must be done well

It's the interpretation that is open to GeoFantasy