Geology!Geology!Like Rocks and Stuff…Like Rocks and Stuff…

What is Geology?What is Geology?

•The study of the “Physical” World and it’s natural processes.

•Earth’s History!

Why Do we care?

What do Geologists study?What do Geologists study?Rocks and Minerals Earthquakes

VolcanoesErosion

Fossils/Earth History

So let’s look at an Earth History So let’s look at an Earth History problem:problem:

Alfred Wagener noticed that several continents seem to fit together really well (like pieces of a puzzle)

In fact, lots of the continents seem to fit together like a HUGE puzzle! Is it just a coincidence?

For example: Africa and SouthAmerican’s coastlines almostLook made for each other…

Fig. 2.05Fig. 2.05

W. W. Norton. Modified from Motz.W. W. Norton. Modified from Motz.

• Also the fossils of the exact same critters were found on two different continents. THAT WERE SEPARATED BY AN OCEAN!!! yeah…that shouldn’t happen…

None of these organisms are ocean living organisms capable of swimming for Thousands of mile. So how did their fossils get so wide spread?

Wagener reasoned that

all of the continents must have

been joined together at some past

time!!!

So…We have two big phenomenon that

are difficult to explain:

1)That the continents look like giant

pieces of a puzzle.2) Fossils of the same

non-swimming organisms found on land separated by an

ocean

Main Concept One: All the

continents used to be

joined together in one large piece called “Pangea”.

Wagener's Wagener's Problem:Problem: How do you

get an entire continent to

move?

In fact, Wagener’s ideas were rejected at first because nobodycould believe there was a force strong enough to move an

entire continent…but then the answer was discovered!

So…think: What force is strong

enough to move entire continents?

No really! THINK for a minute….

Don’t just give up and click through!THINK!!!

What force could be strong enough to move an entire

continent?

So which form of energy makes the So which form of energy makes the Earth’s continents move about?Earth’s continents move about?

Heat Energy!Main Concept Two:

Heat deep in the center of the earth (the Core) creates enough force to drive the process of

change on the surface.

Remember your layers of the Earth Remember your layers of the Earth (from 7(from 7thth grade): grade):

• Inner Core– Solid

• Outer Core– Liquid

• Mantle– Soft Solid

• Crust– Continental (land)– Ocean

HeatHeat energy is what makes energy is what makes motion and change on the Earth’s surface!motion and change on the Earth’s surface!

We already know that when fluid is heated, it moves in a circular motion:

“CONVECTION”

What is Happening below the What is Happening below the earth’s surface?earth’s surface?

Convection within the Mantle!Convection within the Mantle!

Primary Source of Heat Energy

VERY SOFT ROCK

VERY SOFT ROCK

Notice that the rock in theMantle begins to move in

A circular motion = Convection!

Fig. 2.06bFig. 2.06b

W. W. NortonW. W. Norton

As the mantle moves around, the crust “floating” on top of it is “deformed” into different shapes and features!

These features include: Mountains, valleys, canyons,volcanoes, oceans, deep sea trenches, etc…

So how do we get these different So how do we get these different features from mantle movement?features from mantle movement?

• http://education.sdsc.edu/optiputer/flash/convection.htm

• Watch what happens as:– Continents collide. (What is formed?)– Continents “drift” apart. (What is formed?)

Since Wagener’s day we have observed new evidence/phenomena that helps to support his idea that the continents are indeed moving:Some are found on the next few slides…

Evidence #1: We have

discovered that the age of rocks on the sea floor change as you

move away from the middle of the oceans. The youngest

rocks are in the middle; the

oldest are at the edges.

Reds and oranges are the youngest

Blues and greens are the oldest

This is an image of the Atlantic Ocean bottom. The ages of rocks are shown by colors.

Evidence #2: Locations of Earthquakes and Evidence #2: Locations of Earthquakes and Volcanoes infer big cracks in the crust!Volcanoes infer big cracks in the crust!

We call the pieces of crust : “Plates”These “plates” act like floating rafts on the mantle

Motion of PlatesMotion of PlatesEvidence #3: We have used GPS technology

to actually track the movement of land. The arrows show where the areas are currently moving.

There is more evidence, but these three are very convincing!

Where the “plates” touch each other, they form three types of cracks/edges that we call:

“boundaries”:

*Divergent: Where two plates move apart

*Convergent: Where two plates collide into each other

*Transform: Where two plates slide past each other.

Divergent Plate BoundaryDivergent Plate Boundary-Most common in the middle of oceans (mid-ocean ridges) In fact,

scientists think this is how new oceans are formed!

-Two plate moving apart from each other

-Many small Volcanoes

-Many small earthquakes

This group of volcanoes used to be closer to the

Mid-Ocean Ridge!

Which group of volcanoes is

probably older?

A? B?

C?

A: C is the oldest!

Notice that the young rock is right down the middle

And the old rock is on the outer edge

Two plates diverging!

The red colors shows the youngest rockand the blue colors show the oldest rock!

Convergent Plate BoundaryConvergent Plate Boundary-Where two plates collide with one another

-Most common at the edge of oceans

-Few, very large earthquakes

-Large volcanoes/ mountains form nearby (tallest places on earth)

-Deep sea trench (deepest places on earth)

What is this dark long feature?

What is all this white stuff on top of?

What are all these little islands?

A: A deep trench!

A: Snow on Mountains

A: Volcanoes!

Ocean Plate colliding with Continental Plate

What has formed here?

Why is there no trench?

Will you find volcanoes here?

A: Very tall mountains!A: Neither plate is going down!

A: Probably not. There is nocrust being melted

Continental Plate colliding with Continental Plate

Transform Plate BoundaryTransform Plate Boundary-Most common between the other plate

boundaries.

-Two plates moving side by side

-“Offset” features help identify movement

-Common medium sized earthquakes

Transform Plate Boundary

“Offset” river