Download Earth Science 4

We Need More Evidence!
Purpose: Prove to yourself
that Earth’s continents really
are moving apart.
Trust No One.
• So far you have heard three pieces of evidence
suggesting that Earth continents are moving.
– Animal Fossils
– Plant Fossils
– Landforms
• BUT is that good enough? What do you
think?
• Be a SKEPTIC, discuss other explanations for
these so called pieces of evidence.
Some more evidence
• One good thing about scientists is
that they don’t give up until they
find the truth. (At least the good,
honest, and true scientists don’t.)
• SO, let us see what they came up
with.
Evidence 1
•
I am going to show you two videos discussing
scientific evidence that the continents are
moving. Please answer the following:
1. Describe in detail what the scientists
observed?
2. Where did they observe it? How big was it?
3. What evidence did they find proving that
what they observed was the cause of the
continents moving apart?
Sea-Floor Spreading
• Other pieces of evidence suggested that the
continents of Africa & S. America had been
attached.
• However, those pieces of evidence did not
explain HOW they MOVED APART.
• Sea-Floor Spreading provides a cause for
the movement of the continents.
Sea-Floor Spreading
• Mid-Atlantic Ridge
– 1 Mile High
– 12,000 Miles Long
– Part of larger 50,000 mile worldwide underwater mountain chain.
• Age of rocks get older the further you
get from the ridge AND younger the
closer you get to the ridge.
SO…
• If the sea-floor is spreading,
does that mean the Earth is
getting larger?
• Choose a side, either yes or no.
• Come up with some ideas to
support your choice.
Even the Earth Recycles!
• Subduction
– The Process through which the
crust plunges back into the Earth.
• Some absorbed by Mantle.
• Some forced upward becoming…
–Volcanoes
–Mountains
Can a Lil’ Crack Do All That?
• Purpose: Can a crack in the
sea floor cause entire
continents to move or is there
more to it?
What do you think?
• Based on what you know so far about the
Earth’s Interior, do you think there could
be more going on inside the Earth than
just Sea-Floor Spreading?
• Spend the next three minutes thinking
about what else could be causing the
continents to drift?
Could we somehow make a model?
• No, we can’t melt rocks, but
can we do something else?
How About A Demonstration?
• I will call you to the front.
10 at a time. While I am
calling groups up please read
pages 376-380. Take Notes.
Explain What You Observed
•
•
•
•
What is heat?
What does it do to the water?
How does the water change?
How does all of this relate to the way the
water moves?
• How does this relate to the movement of the
Earth’s Crust?
Why Does This Motion Occur?
• Convection Currents (Hypothesis)
–The movement of materials due to
differences in temperature.
•High Temp=Higher Energy=
Spread Out=Less Dense=Float
•Low Temp=Lower Energy=
Condense=More Dense= Sink
The Continents get Carried Away
What Happens When the Plates Move?
• Earthquakes
• Volcanoes
• Mountain Building
But Why?
• Please discuss some ideas for
why the movement of Earth’s
plates leads to:
–Earthquakes
–Volcanoes
–Mountains
How About A Video?
• Don’t Forget About Tomorrow’s Lunch Time Review