Name: Date: Tuesday 12/1/15

Topic – Ch4L2 – Development of a Theory (Pages 134-141)• Essential Question (SC.7.E.6.2, SC.7.E.6.4, SC.7.E.6.7)

• How is the seafloor spreading?• Student Objective

I can explain how there is evidence for seafloor spreading• I Do/We Do – Guided notes and Class discussion• You/Do – Student/Teacher choice menu• Do Now

• Do Lesson 1 Review on pg 132• Think about it on pg 134

Development of a Theory

• Remember how much of the evidence for continental drift was on the seafloor?• After world war 2, we were able to explore the seafloor• Done using an echo sounder• A topographic map was able to be made this way

• Echo sounding allowed us to see giant mountains below the ocean’s surface• Mid-ocean ridge: mountain ranges that are in the middle of the

ocean• much larger than those on land

Seafloor spreading

• Seafloor spreading: the process where new oceanic crust forms along a mid-ocean ridge and older oceanic crust moves away from the ridge• Done in the 1960’s• Helped to explain continental drift better than Wegner’s explanation

Seafloor spreading

• Basalt is formed when lava erupts and cools at the mid-ocean ridge on the ocean floor• As eruptions continue to occur, the older crust is pushed away• So what does that tell you about where the oldest and youngest

layers are?

Oceanic Mountains

• The mountains in the mid-ocean ridges are formed in two ways• 1) they can erupt on the ridge and build up along the ridge• 2) as the lava cools and forms new crust, it cracks, forming jagged mountain

ranges

• Sediment does accumulate on the ocean floor• The farther you go away from the mid-ocean ridge, the seafloor

becomes smooth• Forms abyssal plains

The rock layers are magnetized

• Normal polarity: when magnetized objects point north• Reversed polarity: when magnetized objects reverse direction and

point south• Magnetic reversal: this is when the magnetic field reverses direction• This occurs every few hundred thousand – every few million years• A magnetic field is formed by movement of electrons of the molten

iron in the outer core

Extra resources

• https://www.youtube.com/watch?v=6CsTTmvX6mc• https://www.youtube.com/watch?v=BCzCmldiaWQ• https://www.youtube.com/watch?v=K8blL9Ki2mQ• http://earthguide.ucsd.edu/eoc/teachers/t_tectonics/

p_seafloorspreading.html• Brainpop “Ocean Floor”• http://www.divediscover.whoi.edu/history-ocean/continental.html

Chapter StandardsPrimary Standards• SC.7.E.6.2 – Identify the patterns within the rock cycle and relate them to surface events (weathering and erosion)

and sub-surface events (plate tectonics and mountain building)• SC.7.E.6.4 – Explain and give examples of how physical evidence supports scientific theories that Earth has evolved

over geologic time due to natural processes• SC.7.E.6.5 – Explore the scientific theory of plate tectonics by describing how the movement of crustal plates causes

both slow and rapid changes in Earth’s surface, including volcanic eruptions, earthquakes and mountain building• SC.7.E.6.7 – Recognise that heat flow and movement of material within Earth causes earthquakes and volcanic

eruptions, and creates mountains and ocean basins. Secondary Standards• LA.7.2.2.3 the student will organize information related to a topic through charting, mapping, paraphrasing,

summarizing, or comparing/contrasting.• MA.6.A.3.6 Construct and analyze tables, graphs, and equations to describe linear functions and other simple relations

using both common language and algebraic notation. • Data – See Bi-Weekly Analysis

• ESE/504/ELL – Separate Page

Green = On Level Yellow = Below level Blue = Above Level

Vocabulary – 14 words – Chapter 4

Lesson 1 – p126 Lesson 2 – p134 Lesson 3 – p142

1. Pangea2. Continental Drift

1. Mid-Ocean Ridge2. Seafloor spreading3. Normal polarity4. Magnetic reversal5. Reversed polarity

1. Plate tectonics2. Lithosphere3. Divergent,

Transformed, and Convergent plate boundaries

4. Subduction5. Convection6. Ridge push7. Slab Pull