Structure of a Continent Figure 13-3

How are continental plates formed? Figure 13-4

Continent-Ocean Collision

Ocean-Ocean Collision

Antilles Arc

Subduction Zone Jump

Granite plutons begin deep within an orogenic belt. How do they get to the surface? Erosion and Isostatic Rebound!

Discovery of the “roots” of mountains:

“Airy”-style isostasy: density is the same, but the thickness varies (ice cube model) (Good for continental mountains)

“Pratt”-style isostasy: lateral density varies (Good for mid-ocean ridges)

Ocean gravity map gives seafloor bathymetry.

World topography is mostly in isostatic equilibrium, but not always.

Geoid (meters), from GRACE satellite data

Tectonic history of North America

Eastern Terranes

Highlight 13-2 Tectonic history of North America: Growth of the Appalachians

Geometry of the Pacific – North America plates

Western Terranes

Western Terranes: The Rockies

But subduction is much more shallow than this picture shows!

Where does heating come from? Western Terranes: Basin and Range

Canadian Rockies Appalachians Alps

Volcanism adds rock to continental volume.

Hotspot volcanism often begins with a large basaltic flood.

Afar hotspot

Columbia flood basalts

Columbia flood basalts: Beginning of Yellowstone hotspot

Shape of Atlantic Ocean determined by Iceland hotspot