{[ promptMessage ]}

Bookmark it

{[ promptMessage ]}

Continental Drift - Continental Drift Wegener The Origin of...

Info iconThis preview shows pages 1–3. Sign up to view the full content.

View Full Document Right Arrow Icon
Continental Drift - Wegener “The Origin of Continents and Ocean” - Wegener proposed supercontinent of Pangea o Breakup about 20,000 yrs ago o Spead about 30m. year o Continents “float” on top of oceanic crust o Jigsaw puzzle fit of continents o Similar rock assemblages across ocean - When Wegener hypothesized continental drift, he thought which of the following about continents? o They “float” on top of oceanic crust o They used to be closer together than they are today Why Continental drift didn’t work o No sufficient force to move continents o Additional evidence drives new ideas: Convection in the mantle Seafloor spreading Plate Tectonics o Identifying seafloor spreading Seafloor is made of young basalt Mapping of long “crack” running through the Atlantic Later became known as the Mid-Atlantic Ridge Marie Tharp thinks the long crack is a rift valley o The crust is separating and pulling apart o She is initially dismissed o Almost all earthquakes in Atlantic Ocean are along the “crack”
Background image of page 1

Info iconThis preview has intentionally blurred sections. Sign up to view the full version.

View Full Document Right Arrow Icon
o b/c earthquakes are produced during active faulting, the “crack” must be active o Marie Tharp is vindicated Hess and Dietz, early 1960s o Crust seperates at mid-ocean ridges o New crust is formed by upwelling magma o New seafloor spreads away from rift o If crust is always being formed at mid ocean ridges, is the earth expanding? Or is the seafloor being recycled somewhere? o Ocean crust is being recycled o Related to intense volcanism and earthquakes o C oncentrated on margins of the Pacific Ocean- “The Ring of Fire” The Theory of Plate Tectonics o The
Background image of page 2
Image of page 3
This is the end of the preview. Sign up to access the rest of the document.

{[ snackBarMessage ]}