Ch 10 Plate Tectonics

• Section 10.1

Continental Drift

continental drift - a hypothesis proposed in 1912 by German meteorologist,

Alfred Wegener

Continental Drift

one landmass called Pangaeaone ocean called Panthalassa

Continental Drift

Based on: rock clues fossil clues climate clues

Pangaea

Pangaea

Pangaea

Rock clues

Rock clues

Fossil clues

Fossil clues

Glossopteris

Climate clues

Continental Drift Theory

Evidence:Puzzle-like fit of continentsIdentical fossils & rock structure on various

continentsGlacial deposits in present-day tropical climatesCoal deposits in present-day temperate climates

Wegener’s idea was rejected in early 1900’s –

because he could not answer:

“What caused the continents to move?”

“How, when, or why did continents move?”

Sea Floor Spreading

1947 – rocks on ocean floor found to be younger than continental rocks

1960 – Princeton U. – Harry Hess – proposed theory of Seafloor Spreading – if seafloor is moving, continents may also be moving

mid-1960’s – paleomagnetic reversal time scale developed for continental rock matches that of rocks found on sea floor

The Geomagnetic Reversal Time Scale

Discovery of Sea-Floor Spreading

Sea-Floor Spreading