Alfred W.

"Doesn't the east coast of South America fit exactly against the west coast of Africa, as if they had once been joined?”"This is an idea I'll have to pursue.”- letter to his future wife, December 1910

Alfred Lothar Wegener (1880-1930)

Turns out, he wasn’t the first. Francis Bacon noticed this in the 1600s.

In 1858, geographer Antonio Snider-Pellegrini made these two maps showing his version of how the American and African continents may once have fit together, then later separated.

Evidence for continental drift:1) The shapes of continents match2) The rocks match3) The plants match4) The ice matchesYet, the current positions don’t match

A younger Alfred

A ghoulish Alfred

A colder Alfred

Glacial evidence

This all lead to a theory…CONTINENTAL DRIFT

The continents have movedaround the globe over time.

They were all together about 250Million years ago (I’ll call it Pangea, meaning “all the Earth” in Greek)

There was a southern mega-continent (Gondwana) and a northern mega-continent(Laurasia).

…and a whole lot of criticism.

"Utter, damned rot!” -W.B. Scott

"If we are to believe [this] hypothesis, we must forget everything we have learned in the last 70 years and start all over again” -American scientist

"Wegener's hypothesis in general is of the footloose type, in that it takes considerable liberty with our globe, and is less bound by restrictions or tied down by awkward, ugly facts than most of its rival theories." - Dr. Rollin T. Chamberlin, University of Chicago

I’ve seen better filmson laundry detergent.

This sounds likeour kind of criticism.

A break in the action:What makes a good scientific

theory?Scientific Theory - A hypothesis or group of hypotheses

that: 1) Explains scientific observations; 2) Is tested with repeated experiments and observations and found always to work; and 3) Is accepted by the scientific community.

A good scientific theory:1) Logical consistency 2) Agrees with the data.3) Verifiable causes that explain and predict 4) Advanced comparisons (simplicity, tradeoff of

generality and specificity, distinction between non-fatal difficulties and fatal difficulties)

Is continental drift a good theory?

- Self consistent- Agreed with available data- Made specific, testable predictions- Had difficulties, but weren’t fatal ones

Do you think peopleknow that we startedour careers as German arcticmeterologists, Statler?

Ah, to be youngand freezing coldagain, Waldorf.

Implications1) The older concept of land bridges to explain fossil

distributions became less likely.2) The concept of a mobilistic Earth is brought

forward.3) It allowed scientist to start making predictions

about fossil distributions, geological structures, and earthquakes.

It placed an easily comprehensible, tremendously exciting structure of ideas upon a solid foundation. It released the continents from the Earth's core and transformed them into icebergs of gneiss [granite] on a sea of basalt. It let them float and drift, break apart and converge. Where they broke away, cracks, rifts, trenches remain; where they collided, ranges of folded mountains appear.

H. Cloos (famous geologist)

1950s: The bathymetry of the ocean floor.

Marie Tharp

Bruce Heezen

Harry Hess

Fred Vine and Drummand Matthews

1963

In 1967, W. Jason Morgan proposed that the Earth's surface consists of 12 rigid plates that move relative to each other.

Two months later, in 1968, Xavier Le Pichon published a complete model based on 6 major plates with their relative motions.