TodayToday

Hand in any work needed.Hand in any work needed. Check the list in the back, if you owe Check the list in the back, if you owe

something.something. Get out a small piece of paper, PUT Get out a small piece of paper, PUT

YOUR NAME ON IT.YOUR NAME ON IT. When bell rings the quiz will start and you When bell rings the quiz will start and you

will have 1 minute per question to answer.will have 1 minute per question to answer.

Question 1Question 1

What is the density of the 2 types of crust?What is the density of the 2 types of crust?

Question 2Question 2

Evidence of continents moving (2)?Evidence of continents moving (2)?

Question 3Question 3

What element is the crust made out of What element is the crust made out of mostly?mostly?

Question 4Question 4

What is LAT/LONG of Hawaii hot spot?What is LAT/LONG of Hawaii hot spot?

AnswersAnswers

What is the density of the 2 types of crust?What is the density of the 2 types of crust? 3.0=oceanic 2.7=cont3.0=oceanic 2.7=cont

Evidence of continents moving (2)?Evidence of continents moving (2)? Puzzle, fossils, mtns, sea floor spreadingPuzzle, fossils, mtns, sea floor spreading

What element is the crust made out of What element is the crust made out of mostly?mostly? OxygenOxygen

What is LAT/LONG of Hawaii hot spot?What is LAT/LONG of Hawaii hot spot? 2020ooN 160N 160ooWW

Sea Floor SpreadingSea Floor Spreading

And Other Plate BoundariesAnd Other Plate Boundaries

Continental driftContinental drift Idea that continents “floated” on the Idea that continents “floated” on the

ocean and moved into current locations.ocean and moved into current locations.

This idea was argued against from its This idea was argued against from its beginning.beginning. The ocean floor was thought to be flatThe ocean floor was thought to be flat How can the continents move? They are so big?!How can the continents move? They are so big?!

Alfred Wegner- 1912 - Continents float. 1912 - Continents float.

Continental DriftContinental Drift

Hess’s DiscoveryHess’s Discovery

In the 1950’s a Naval Captain In the 1950’s a Naval Captain Henry Hess made a discovery.made a discovery.

Hess found that the ocean floor Hess found that the ocean floor was was notnot flat at all. flat at all.

Further research proved that it was in fact Further research proved that it was in fact like a mountain range. like a mountain range. DEMO

New idea?New idea? Scientists looked at the Scientists looked at the

continental shelfcontinental shelf and saw and saw the pieces fit together much the pieces fit together much better.better.

We call this We call this Plate Tectonics not not Continental Drift

Plate tectonics is the Plate tectonics is the movement of the movement of the plates on the mantle!plates on the mantle!

New technology allowed New technology allowed scientists to see another fact scientists to see another fact called called paleo-magnetism.

Gabbro verses a compassGabbro verses a compass What is the composition of gabbro?What is the composition of gabbro? So the Iron in it should always be aligned So the Iron in it should always be aligned

to the polarity of the Earth?to the polarity of the Earth?

If we put a compass on the If we put a compass on the

rock it will show the rock it will show the

magnetic field that was magnetic field that was

frozen into the rock when frozen into the rock when

it formed.it formed.

How does that explain anything?How does that explain anything? If I took water and put iron in it and If I took water and put iron in it and

then froze it the iron would be the then froze it the iron would be the same direction.same direction. But if I put it in and before I froze it, But if I put it in and before I froze it,

then switched the field around the ice then switched the field around the ice tray the iron would align and refreeze tray the iron would align and refreeze the opposite way!the opposite way!

If the fields in the rock have been If the fields in the rock have been flipped then this mean the fields flipped then this mean the fields on Earth have been flipped!on Earth have been flipped!

How does this work?How does this work?

ConvectionConvection moves the plates moves the plates New magma fills the empty space creating the empty space creating

new rock.new rock. This new rock saves the magnetic field

around Earth at that time.around Earth at that time.

**Think of a grocery stores check out.****Think of a grocery stores check out.**

Paleo-MagnetismPaleo-Magnetism Using the Earth’s recorded magnetic field in rocks

to understand the past. This is what the scientists inferred to be happening

Balloon demo

North wasn’t always North!North wasn’t always North!

Magnetic reversalsMagnetic reversals Looking at the rocks around these ridges Looking at the rocks around these ridges

we can see that the polarity in the rocks we can see that the polarity in the rocks has switched.has switched.

Mid-Atlantic Ridge

This is a region of the Earth’s surface is This is a region of the Earth’s surface is also called a divergent plate boundary.also called a divergent plate boundary.

Divergent Plate boundaryDivergent Plate boundary

What causes these plates to move?What causes these plates to move?

Convection – Drives these plates – Drives these plates Lava LampLava Lamp

View of under the oceanView of under the ocean