The last hurrah

the debatecontinental drift

the “Bullard” filtseafloor spreading

Ice Age

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uniformitarianism catastrophism

Alfred Wegener Arthur HolmesBertram Boltwood

Walter ElsasserEdward Bullard

Harry HessMcKenzie, Vine, MathewsTuzo Wilson

the “erratics”Ice Age modelastronomical theory of Ice Age

uniformitarianism

catastrophism1

youtube tag: Ice Age 4 COntinental drift trailer

UniformitarianismEarth is gradually shrinking, contract ing as i t coo led , producing mountain ranges as it wrinkled and shrank

catastrophismsudden and rapid bursts of dramatic change separated by long intervals of relatively calm cooling, contracting Earth

James DanaEduard Seuss

Continents have always been continents,

seafloor have always been seafloor.

Contraction is the driving force for

rapid bursts separated by long intervals of calm contracting Earth.

James Dana

Earth is gradually shrinking, contracting as

it cooled, producing mountain ranges as it wrinkled and shrank

-permanentism-

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Eduard Seuss

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sudden and rapid bursts of dramatic change separated

by long intervals of relatively calm cooling,

contracting Earth

-gondwanaland-

Eduard Seuss

1

for this to happen, T = 1200oC

Gondwana lead to Continental drift idea

Australia India Africa

Antonio Snider-Pellergini

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series of catastrophes took place on Earth

the Great Flood

Antonio Snider-Pellergini

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first to publish a map which brings together

continents on both sides of Atlantic Ocean

the map is used to explain the similarities between fossils in land masses separated by

oceans

Osmond Fisher1

Moon was formed when young Earth split into two

unequal parts

the hole left behind by the Moon drove the continents to move

towards it to fill the empty space

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2 Alfred Wegener

Father of Continental Drift Theory

meteorologist-geologist

the jigsaw puzzle

paleontological similarities

South America West Africa

mesosaurus marsupials

volunteer reserve cadet (meteorological service of army)

youtube tag: Great Minds - Alfred Wegener (SciShow)

2

2 Alfred Wegener

seek out evidence to support his idea

defended the model in light of criticisms

overall concept stood the test of time

2 Alfred Wegener

Pangea - contained all land surface

Whatever is the driving force, he pointed out the sites of rift valleys the process of continental

drift which still continues to take place

up until now

2 Alfred Wegener

argued that the cause of continental drift are:

retreat from poles caused by centrifugal force possible tidal effects

ploughing through the sima of the seafloor

inaccurate measurements (50-100k years)

Arthur Holmes2

Radioactive decay

Convection is associated with mountain building, continental drift theory

Arthur Holmes2

convection current stirred the continents to move very slowly, pushing other continents as

they collide around the globe

PangeaGondwanaland (South)Laurasia (North)

Bertram Boltwood2Geometric dating

age of earth: 4.5byo

accuracy of measurements in

determining the age of rock samples led to

more accurate historical claims

no new evidencesno new ideas

1950s-1960s

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Walter Elsasser3Fossil magnetism (rocks)

Earth’s magnetic field

Edward Bullard3model of Earth’s magnetic

field as product of circulating conducting fluids in hot fluid core

used early electronic computer for 1st numerical

simulation of dynamo process

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Harry Hess4proponent of the

Seafloor Spreading Theory

Ocean ridges are produced by convection currents in the fluid material of the mantle welling up from

deeper below the surface

Harry Hess4direct evidences

accurate measurements

Mountain formation at Pacific ocean floor reverse magnetic polarity as evident in rocks

age of rocks: new ones found at the ridge, older ones at the foot of the ridge Atlantic ridge widening: 2cm/yr

Dan McKenzie

Frederick Vine

Drummond Mathews

4 linked the evidence for geomagnetic reversals with seafloor spreading model of continental drift

suggestive NOT conclusive

Tuzo Wilson4put together the ideas of Continental

Drift and Seafloor Spreading

PLATE rigid portions of Earth’s

crust that move the ground caused by forces associated

with the two theories

Edward Bullard4

objective method using mathematical basis

used electronic computer to provide unbiased objective matching

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Bernard Kuhn5

erraticsBiblical flood

first to notice the erratic formation of polar ice caps

James Hutton Jens

Esmarck

Richard Bernhardi

5 polar ice cap extended as far South as central Germany

Louis Agassiz

“convert” - finally convinced

enthusiasm position - President

Credibility and Influence

5

5 Louis Agassiz

looked for evidences of glaciation

used Johannes Kepler’s Law of Planetary Motion to

explain Alternating Ice Ages

elliptical orbit

5

Alexander Von Humbolt

Joseph Alchemar

Urbain LeVerrier

James Croll

5 Mulitin milankovitch

used mathematical evidences to describe changing climates by comparing the

temperatures of 3 planets

Mars Earth Venus

Wladimir Köppen

published a book containing his attempt to explain the past climates

based on continental drift

5

It is not the temperature in winter but the temperature in

summer that dictates how much snow stays unmelted in summer

ice cold summer NOT extra cold winter

1958

no new geological evidence seemed to matter the idea had fallen out and died down

1970s

20th century

end of classical science and beginning of quantum revolution

the Last Hurrah

end of all the dynamic changes and beginning of a more stable Earth

7the things i learned:

just as the tectonic plates need “driving force” to cause it to move to form the Earth,

!people need a motivation to keep on doing

what they are doing to attain a goal

conscious effort to pursue a problem scientific method is a cycle — a never-ending process of seeking for truth and making sense

HPS Connect


More than what a person is talking about, in order to persuade

his audience, he must: know his audience have credibility be passionate and enthusiastic

theories are conjectures; scientific theories are refutable It is not the correctness or truthfulness, but the usefulness of a theory that matters

HPS Connect


In the end, it doesn’t matter if people believe you or not,

the more valuable is the passion to seek for truth and the patience

to bear the rigorous work that goes with it.

Science has a way to correct itself Discovery consists of seeing what everybody has seen and thinking what nobody has thought

HPS Connect

Education

The last hurrah