Notebook Setup On pages 28 – 29, glue down the “Physical Geography: Plate Tectonics” worksheets On pages 30 – 31, glue down the “Oreo Cookies and Plate Tectonics” worksheets

Warmup What is the “truth”? How do you define “truth” and is it debatable? Is your “truth” different from someone else’s “truth”?

Physical Geography Plate Tectonics

Geologic Time January 1 - Earth and planets formed Pretend the age of the earth (4.6+ billion years) is compressed into one calendar year. January 1 - Earth and planets formed Early March - liquid water stands in pools. Late March - earliest life July - oxygen is important part of atmosphere October 25 – multi-cellular organisms Late November - plants and animals abundant December 15 to 25 - dinosaurs arise and disappear 11:20 pm, December 31 - Humans appear One second before midnight - Automobile invented

What is ‘tectonics’? The word “tectonics” comes from the Greek ‘tektonikus’, meaning “building or construction” Plate tectonics refers to the process of earth crust formation, movement, and destruction.

What is a ‘Plate?’ Lithospheric plate: crust + upper mantle Asthenosphere: plastic mantle

History of Plate Tectonics ‘Fit’ of coastlines was recognized by Sir Francis Bacon in the 1600s But how did the continents move?

1915 = Alfred Wegener proposed the theory of continental drift. Supercontinent Pangaea (‘all-earth’) [225mya]. Fragmentation and drift to current positions.

Plate Movement History

STOP: Answer this question What would scientists need to find to prove that the continents were once connected? Check with your neighbor to see what they thought scientists should look at.

Wegener’s Evidence Fit of continents Fossil plants, animals, rock types / geology matched on opposite shores deposits inconsistent with current geography

Striking Match of Geologic Regions

Striking Match of Biological Regions

History of Plate Tectonics Main problem with the theory of plate tectonics: Couldn’t explain how the continents ‘drift’! Wegner hypothesized spin of Earth or tides…..

History of Plate Tectonics Arthur Holmes (1930s) came up with a new theory of motion: Thermal convective cells in the upper mantle (aesthenosphere) theory is largely ignored

History of Plate Tectonics In the 1960s, Harry Hess and Robert Deitz (geophysicists) proposed sea floor spreading along mid-oceanic ridges for plate motion.

Sea Floor Spreading

STOP: Answer the question If the sea floor is spreading in some places, what’s happening in other places? Is Earth getting bigger? What do your neighbors think about your ideas?

Plate Tectonics Theory Continental Drift + Sea Floor Spreading  Theory of Plate Tectonics

Plate Tectonics Theory Plate boundaries: main location for Earth’s volcanic and earthquake activity. This is the main place where mountains are created. Type of plate boundary determines activity. 3 types: diverging (spreading) converging (colliding) transform (sliding)

Geography of the Plates 7 major plates; several minor plates Small plates / boundaries still unknown

Plate Margins: how do we know? Marked by volcanic and tectonic activity

Convergent Plate Boundaries Activity: 1) Subduction (heavier plate dives under another) 2) Earthquakes 3) Volcanism Features: 1) Ocean trench 2) Explosive volcanic mountains

Convergent Plate Boundaries Examples: Himalaya Mountains Andes Mountains Ring of Fire

Divergent Plate Boundaries Landscape features: Land: rift valleys, volcanic mountains, thinning crust Ocean/sea: rift valleys, mountain ranges

Divergent Plate Boundaries Examples: Atlantic Mid-Oceanic Ridge Red Sea Rift valleys of eastern Africa

Transform Plate Boundary Activity: Two plates slip past each other; Earthquakes Features: Faults Example: San Andreas Fault, California

Activity! DON’T EAT THE OREO! I will not give you another one! Try to keep your Oreo crumbs on the plate Try to be careful with twisting off the Oreo top so it doesn’t break right away