for example,the carbon cycle cycles CO₂from the air into living material, into the ocean,eventually into the rocks (limestone),and then back again

o need to understand how the Earth moves

■ what is the energy source for this?(described in lecture #2)

■ what is the rock cycle?(described in last lecture)

Modern concept of Plate Tectonics

·    early observations of what was then called Continental Drift

o Alfred Wegener proposed a hypothesis called Continental Drift in 1924

■ observed that the continents seemed to fit together if the oceans were removed from maps

■ was the first to describe it in detail scientifically,but not the first to note this: Abraham  Ortelius(1596),Francis  Bacon(1625),Benjamin  Franklin

(1858),Antonio   Snider-Pellegrini(1858)

first known illustration of the Opening of the Atlantic Ocean by Antonio Snider-Pellegrini,1858

■  Wegner had more information/data than those earlier scientists

he  noted  similar  geology  on  these  continents  as  if  they  were  formed  at the  same  location

he observed data of similar fossils and species on both continents other  evidence:

-ancient climate zones  (coral  reefs  and  deserts)

-glaciations (location and direction of glaciers impossible in current climate)

-“polar   wandering”(shown    below)

o   skeptics  of Continental Drift said:

■  there was no explanation of the energy source

■  there was no ability to refute a claim that plants and animals may have just migrated

■  there was no data/information included about the sea floor

how does something as large as a continent just plow its way through the ocean floor!?

after all,could the continental fit just be a coincidence?

much debate and the hypothesis eventually died

that is all part of the scientific process!

IV.Scientific Method

·    allows hypotheses to be tested and debated

● the good ones hold up and the weak ones die out

● does not imply that scientists are unsure

·    does  imply that scientists are constantly testing new and better ideas

o it is NOT a closed-door or closed-minded approach

·    so,how  did  the  Continental  Drift Hypothesis eventually lead to the Theory of Plate Tectonics??

o more data were collected decades after Continental Drift died away

■ in the early 1960's it was noted that the sea floor appeared to be spreading from its center (data from submarines and satellites)

younger rocks at the center ridge and older rocks near the continents known as the Sea Floor Spreading Hypothesis

could that be linked to the movement of the continents?

0       10        20          33   40    4856              69           83                               118127132142150157 age in millions of years

180

■ lead to the proposal that the mantle of the Earth was convecting much like water boiling on the stove top

driven by the Earth's internal heat

this was the driving force (energy)that Wegner lacked for his hypothesis  the movement of the mantle created new ocean floor crust,which spread out and pushed the passive continents along

■ this then became the unifying theory for the geosciences:Theory of Plate Tectonics (but only in the late 1960s!)

·General  Stages  of  the  Scientific  Method

1.observation   &data   collection

■ example:

Wegner's original observations

geophysical data from the sea floor in the 1960's

2.hypothesis

■ example:

ocean floor created at the center,destroyed at the edges

▶ continental crust therefore must move as part of this process

3.prediction

■ example:

if the sea floor was being created at the middle,then it must be older at the edges (was that true?)