1. Add the new notes to your table of contents, and then turn to the next clean page and set up your title and date
8C: Plate Tectonics

2. Add hypothesis and theory to your index
Example:
Hypothesis of Continental Drift
Examples:
Gravitational Theory
Cell Theory
Evolutionary Theory
Hypothesis
Theory
A possible explanation about an observation that can be tested by scientific investigations
An explanation of observations or events based on knowledge gained from many observations and investigations

3. Add hypothesis and theory to your index
Example:
Hypothesis of Continental Drift
Examples:
Theory of Plate Tectonics Gravitational Theory
Cell Theory
Evolutionary Theory
Hypothesis
Theory
A possible explanation about an observation that can be tested by scientific investigations
An explanation of observations or events based on knowledge gained from many observations and investigations

4. Hypothesis vs Theory
A hypothesis is a testable idea. Scientists do not set out to “prove” hypotheses, but to test them. Often multiple hypotheses are posed to explain phenomena and the goal of research is to eliminate the incorrect ones. Hypotheses come and go by the thousands, but theories often remain to be tested and modified for decades or centuries. In science, theories are never hunches or guesses and to describe evolution as “just a theory” is inappropriate.
A theory is an explanation. The validity of a theory rests upon its ability to explain phenomena. Theories may be supported, rejected, or modified, based on new evidence. Gravitational theory, for example, attempts to explain the nature of gravity. Cell theory explains the workings of cells. Evolutionary theory explains the history of life on Earth.

5. Add plate tectonics to your index of key terms
Plate Motion
The theory of plate tectonics states that Earth’s crust is broken into rigid plates (tectonic plates) that move slowly over Earth’s surface.
The movement of one plate is described as either moving away from or toward another plate, or sliding past another plate.
Plates move at speeds of only a few centimeters per year. At this rate, it takes moving plates millions of years to make new continents, new mountain ranges, or other landforms.

7. Alfred Wegener and Continental Drift
Long before geologists proposed the theory of plate tectonics, they discovered evidence of continental movement.

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9. In 1912, before the Theory of Plate Tectonics came to be, Alfred Wegener developed the hypothesis that continents move, called continental drift

11. Fossil Evidence Geological Evidence
Wegener used different types of evidence to back up his hypothesis
Fossil Evidence
Geological Evidence
fossils of the same ancient plant existed on different continents
similar rocks are found on two distant continents
fossils of fresh water reptiles are found on continents separated by a vast ocean
locations of ancient glaciers, as well as mineral deposits can be traced from one continent to the next
fossils of other similar animals are found on continents separated by vast oceans
matching coastlines and mountain ranges on separated continents

12. When fossil and rock evidence is viewed with today’s continents, they appear to be random, only when viewed as past connected continents, do they make sense.
Even with all of this evidence, Wegener could not convince the other scientists of his time that he was right
This was mainly because he could not explain how the continents were moving

13. Harry Hess made it happen!!!
How did the Hypothesis of Continental Drift become the Theory of Plate Tectonics?
Harry Hess made it happen!!!
Harry Hess was a geologist and Navy submarine commander during WWII
In 1960, he proposed that the continents move due to sea-floor spreading
This provided the evidence Wegner’s original hypothesis lacked, this proved HOW the continents were moving!!!

15. Convection Currents and Sea-Floor Spreading
Convection is the circulation of particles within a material caused by differences in thermal energy and density (think boiling water)
Convection affects the mantle underneath tectonic plates
Hotter mantle is less dense and therefore rises toward Earth’s surface while cooler mantle is more dense and sinks deeper into the mantle

16. Add seafloor spreading to your index
As the Earth’s mantle moves, it pushes and pulls tectonic plates over Earth’s surface.
Tectonic processes continually generate new sea floor at ridges and destroy old sea floor at trenches.
This is what causes sea-floor spreading!
Add seafloor spreading to your index
As the convection currents in the mantle move the molten material, the lithosphere moves on the surface of Earth

18. Mid Ocean Ridge
Mid Ocean Ridge
Underwater mountain range where molten material from the mantle rises to the ocean floor, creating new rock
Subduction Zone
Area where one tectonic plate slides underneath another, sinking back into the mantle and becoming molten material again
Oceanic Trench
Long, deep depression at the edge of the ocean, where oceanic crust subducts below continental crust