Plate Tectonics Continental Drift

Plate Tectonics Chapter 17

Early Ideas Abraham Ortelius Eduard Suess Alfred Wegener Late 1500’s Dutch mapmaker Noticed N & S America seemed to fit with Europe & Africa Thought they were separated by quakes & floods Eduard Suess Late 1800’s Australian geologist Proposed Gondwanaland All southern continents were once joined Alfred Wegener Early 1900’s German scientist Proposed Continental Drift hypothesis

Continental Drift Proposed by Wegener in 1912 Stated that all Earth’s continents were once joined in a single landmass called Pangaea pan → all gaea → Earth Continents broke apart 200 mya and moved to present position

Evidences of Continental Drift Jigsaw fit of continents Rock formations Similar rock structures & types on separate continents Mountain ranges Coal deposits Fossils Same species on different continents with different climates, separated by salt water Climate evidence Coal deposits: form in temperate swamps, now in Antarctica Glacial deposits in tropical areas (no glaciers there now)

Jigsaw Fit

Rock Evidence

Climate Evidence

Why was Wegener’s hypothesis not accepted? Too many unanswered questions What caused continents to move? Earth’s rotation, maybe? Proved NO How could continents push through ocean floor? Wouldn’t this cause fractures? None found then. Hypothesis thrown out by most until 1960’s