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Speaker 1: This Day in History Class. It's a production of I

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Speaker 1: Heart Radio. Hey everyone, welcome to the podcast. I'm Eves

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Speaker 1: and you're listening to This Day in History Class, a

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Speaker 1: podcast that really takes to heart the phrase you learn

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Speaker 1: something new every day. Today is January six. The day

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Speaker 1: was January six, nineteen twelves. German geophysicist and meteorologist Alfred

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Speaker 1: Wegner first presented his hypothesis on continental drift in a

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Speaker 1: public lecture. Wagner advanced the hypothesis of continental drift, but

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Speaker 1: he was not the first to propose that continents gradually

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Speaker 1: drifted across Earth's surface. Wagner's hypothesis was largely rejected by

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Speaker 1: the scientific community, but it did influence the development of

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Speaker 1: the theory of plate tectonics. For centuries, people have record

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Speaker 1: noyes that the coastlines of the continents could fit together

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Speaker 1: as if they were puzzle pieces. Wagner recognized this, and

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Speaker 1: around nineteen ten he became interested in looking into the

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Speaker 1: reason behind the observation. He came across the idea that

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Speaker 1: Africa and South America were once connected by a huge

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Speaker 1: land bridge. He also read about the similarities between fossils

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Speaker 1: on different continents and he noticed that Greenland had drifted

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Speaker 1: away from Europe, and that San Diego and Shanghai we're

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Speaker 1: getting closer to one another over the years. Geological features

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Speaker 1: also matched each other when continents were brought together, but

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Speaker 1: he rejected the idea that land bridges between continents just

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Speaker 1: sank and disappeared. After reading about other lengths between continents,

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Speaker 1: Wagner became convinced that all the continents were once joined

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Speaker 1: as a single continent. The lecture he presented on January sixth,

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Speaker 1: nineteen twelve, at a meeting of the Geological Association in

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Speaker 1: Frankfurt was called the Uprising of Large Features of Earth's crust,

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Speaker 1: Continents and Oceans on geophysical basis. Three years later he

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Speaker 1: published the book The Origin of Continents and Oceans. He

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Speaker 1: proposed that there was one big or continent surrounded by

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Speaker 1: a global ocean. According to his hypothesis, the massive continent

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Speaker 1: began to split about two hundred million years ago, and

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Speaker 1: the newly formed continents never stopped drifting apart. He called

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Speaker 1: this movement continental displacement. He turned to fossils, geologic evidence,

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Speaker 1: and climatology to support continental drift, but people largely opposed

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Speaker 1: the idea. That was partly because Wagner did not have

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Speaker 1: a good model for how the continents moved apart. He

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Speaker 1: suggested that gravitational pool and centrifugal entitled forces moved the

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Speaker 1: continents through Earth's crust, but that was an unbelievable proposal.

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Speaker 1: If continents plowed through the oceanic crust, then they would

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Speaker 1: be distorted, and centrifugal entitle forces were likely too weak

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Speaker 1: to move continents. There was no direct evidence at the

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Speaker 1: time for the movement of the continents, and there was

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Speaker 1: no known mechanism that would be able to move entire continents.

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Speaker 1: On top of this, Wagner miscalculated the rate at which

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Speaker 1: North America and Europe were moving apart. Though some people

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Speaker 1: supported his explanation, most geologists stuck to the hypothesis of

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Speaker 1: static continents and land bridges. Wagner died in nineteen thirty.

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Speaker 1: It wasn't until the nineteen fifties when scientists returned to

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Speaker 1: the theory of continental drift as they explored the ocean floor.

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Speaker 1: Wagner's hypothesis wasn't completely off. For instance, continental movement did

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Speaker 1: have a hand in the creation of mountains, just not

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Speaker 1: as he suggested. Now. Plate tectonics is the most widely

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Speaker 1: accepted theory. It says that Earth's crust is split into

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Speaker 1: rigid moving plates that move slowly over the underlying mantle.

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Speaker 1: While the continent do move, as Wagner and others before

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Speaker 1: him proposed, so does the oceanic crust. The driving force

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Speaker 1: for the motion is likely conviction currents and the magma

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Speaker 1: of the upper mantle. I'm Eave Jeff Coote, and hopefully

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Speaker 1: you know a little more about history today than you

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Speaker 1: did it yesterday. You can find us on social media

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Speaker 1: and Facebook, and you can email us at this Day

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Speaker 1: at I heart media dot com. Thanks again for listening,

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Speaker 1: and have a fantastic twenty four hours until we see

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