Where We Are

Where we are • Today: Drifting Continents • Friday: Plate Tectonics • Last week: Mountain Building, Earth Resources, Global Warming – Course Evaluation - Last day; don’t forget!!

Drifting Plates (Wegener) to Plate Tectonics Some scholars of science have used the story of the origin of plate tectonic theory as an example of a “Kuhnian revolution” Was it?

Kuhnian Revolutions • Science is not a steady, cumulative acquisition of knowledge. • Science is "a series of peaceful interludes punctuated by intellectually violent revolutions,“ • After such revolutions, "one conceptual world view is replaced by another." Thomas S. Kuhn, “The Structure of Scientific Revolutions”, 1962

Kuhn: A Scientific Paradigm • a collection of beliefs shared by scientists, a set of agreements about how problems are to be understood. • essential to scientific inquiry • a paradigm guides the research efforts of scientific communities, and it is this criterion that most clearly identifies a field as a science.

Kuhn: Paradigm Shift • When a paradigm shift takes place, "a scientist's world is qualitatively transformed [and] quantitatively enriched by fundamental novelties of either fact or theory."

From Drifting Continents… • Benjamin Franklin wrote in 1782: • “The crust of the Earth must be a shell floating on a fluid interior. Thus, the surface of the globe would be capable of being broken and disordered by the violent movements of the fluids on which it rested.”

From Drifting Continents… 1. first conception of the revolutionary theory of plate tectonics supported by evidence was proposed by the German geophysicist-meteorologist Alfred Wegener (1880-1930)

From Drifting Continents… • •

CD/PT Video Groups of three: A. What are three lines of evidence Wegener used for Continental Drift? B. What is seafloor spreading? How do transform faults behave oddly at the MidOcean Ridge? C. What was the key development that led to our current theory of Plate Tectonics?

To the video

...to Plate Tectonics A. What are the lines of evidence Wegener used to support Continental Drift? B. What is seafloor spreading? How do transform faults behave oddly at the Mid-Ocean Ridge? C. What was the key development that led to our current theory of Plate Tectonics?

Your Answers to the Drift Rejection Question • It shows that science is based much off logic and reason, and if a "proof" can not be logically proved, then it can be rejected regardless if it is true or false.

Your Answers to the Drift Rejection Question • It shows that without enough evidence, only guesses can be made about why things occur. The scientists just didn't have enough evidence that could explain why things were the way they were. Now days we have satellites, and submersibles and other types of data collecting devices which helps us see the bigger picture.

Your Answers to the Drift Rejection Question • It shows that through proving things wrong, scientists are getting closer to the truth. Wegener had hypotheses that were eventually proved wrong, but knowing that those hypotheses are wrong narrows down the answers to the correct answer.

Your Answers to the Drift Rejection Question • The story indicates that science is a complex subject in itself and when one hypothesizes about something they must have evidence to support what their findings and results show. There has to be plausible explanation as to why the hypothesis makes sense ... however, that's only a start and a lot more has to be proven before the hypothesis is accepted as a theory.

In a nutshell... •“Extraordinary claims require extraordinary evidence” - Carl Sagan

Review of Plate Tectonics • What drives Earth processes? – gravity and density differences – external (e.g. hydrologic cycle, erosion) – internal (e.g. mantle convection)

Review • Plate Boundaries – divergent (AKA constructive) – transform – convergent (AKA destructive) • ocean-ocean (e.g. Mariana Islands) • ocean-continent (e.g. Pacific-North America) • continent-continent (e.g. India-Asia)

Plate Boundaries • divergent (e.g. mid-Atlantic ridge) • transform (e.g. San Andreas fault zone) • convergent • ocean-ocean (e.g. Pacific-Pacific near Marianas Islands) • ocean-continent (e.g. Pacific-North America) • continent-continent (e.g. India-Asia)