Transcript Chapter 17 - MrFuglestad

Chapter 17
Plate Tectonics
Structure of the Earth
Drifting Continents




The Earth’s continents move
16 century mapmaker Abraham Ortelius
noticed the “fit” of the continents.
19th century Eduard Sues proposed an
ancient landmass named Gondwanaland.
1912 – Alfred Wegener proposed the
hypothesis of Continental Drift.
Continental Drift


Wegener proposed that all continents were
once joined in supercontinent called
Pangea.
He was one of the first to propose that the
continents are drifting on the Earth’s
surface.
Continental Drift Evidence





Rock formations (coal beds, sedimentary
rocks)
Climate evidence (glacial deposits)
Fossil evidence (same animals)
Shapes of continents
Paleomagnetism – The study of the Earth’s
magnetic field history through iron bearing
rocks.
Seafloor spreading




In the 1940’s and 1950’s scientists found out
that there are mountains in the center of the
Atlantic Ocean (Mid-Ocean ridge).
Sea floor spreading occurs at the MidOcean ridge and new land is being formed
by volcanoes.
Scientists used a magnetometer to find that
magnetic reversals occur on Earth.
Another view of magnetic reversals
Seafloor Spreading



Scientists also found that there is more
sediment on the sea floor as you move
away from the Mid-Ocean ridge.
Scientists map the age of the rocks on the
ocean floor with isochrons.
An isochron is line on a map that connects
points that have the same age.
The Missing Link


Sea floor spreading explains how the
continents move across the surface.
The plates (the rigid mantle) slide across the
Asthenosphere.
Plate Tectonics



Theory of Plate Tectonics states that Earth’s
crust and rigid upper mantle are broken into
enormous slabs called plates.
There about 12 major plates, and some
smaller plates.
These plates interact at plate boundaries.
Plate Tectonics


Major unifying Geology theory that explains:
Volcanoes
Mountain ranges
Mid-Atlantic ridge and rift valleys
Trenches
Island arcs
Continental Drift

Show video Fearless Planet - last chapter





Look see
Current continents
Plate boundaries
Future continents?
Earthquakes & Volcanoes
Growth of a continent

Subducting plates
 Crashing continents

View video Mountains:




Ethiopian Highlands
Andes
Rockies in summer
Alps
Hotspot
Ridge
Trench
Plate Movements

Volcanism
 Plate movement



Inside the Volcano
 Ring of Fire
Ocean Deep
 Ocean Vents
Inside the Volcano
 Iceland