ES 144: NOTES
September 14, 2012
LECTURE 4: PLATE TECTONICS (THEORY AND EARLY EVIDENCE)
Abraham Ortelius (1596) Theory of continental drift.
Idea bounced around w/ (Bacon, Franklin, SniderPelligrini)
Edwards Seuss – Started to put the ‘puzzle’ together. He found marine fossils in mountains and
questioned why – discovering later there use to be an ocean there. Found more evidence of cont.
drift > fern growth on bunch of continents.
Founded contraction hypothesis compared Earth to apple New and shiny and smooth,
once old, like an apple, the cracks became filled with the ocean.
Alfred Wegener (1912) Arctic explore. Main idea (continental drift.) Questioned “All stuck
together then drifted apart” This land was called PANGEA. (200 mya)
Proved true in a way, instead of land fitting together it is the continental shelves that fit
Mountains = Appalachian Mountains extend to Greenland, Norway, UK… indicating
they were once linked.
Glaciers = More geological evidence: looking at tips and glacier deposits. (Though giant
glacier on tips and top of Antarctica)
>2 theory: Ice age Whole world covered in ice.
Fossil Evidence = Fern species, other animals species. Wegener thought since land was
connected it spread throughout land. (Naïve people argued these animals all swam
Lines of evidence:
Fit of continents
Matching Mt. sequences
Evidence of glaciers
Ice age & Cont. moved
D.C and Paris moving away from each other every year we move 6 cm (finger nail growth
Mechanisms and doubt:
Continents “plowed through Ocean basins
Calcs. Showed incorrect.
Continents move because of gravitational attraction of equator and sun/moon.
Gravitational forces are too small, man on moon before we accepted this
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Structure of Earth > all about density:
Earth has distinct layer