HISTORY OF THE CONTINENTS Grotzinger • Jordan Understanding Earth Seventh Edition Chapter 10: HISTORY OF THE CONTINENTS © 2014 by W. H. Freeman and Company

History of the Continents Chapter 10: History of the Continents

About Evolution of the Continents Nearly two-thirds of the Earth’s surface – all of the oceanic crust – was formed over the past 200 million years. However, rocks of the continents are much older, as old as 4 billion years. Studying the continents tells us how the continental lithosphere formed and evolved.

Lecture Outline The structure of North America 2. Tectonic provinces around the world 3. How continents grow 4. How continents are modified 5. Origin of cratons 6. Deep structure of the continents

● The stable interior ● Canadian shield ● interior platform The Structure of North America ● The stable interior ● Canadian shield ● interior platform ● basins and uplifts

The Structure of North America ● The Appalachian fold belt ● Valley and ridge province ● Blue ridge province ● Piedmont ● Coastal Plain & Continental Shelf

● The North American cordillera ● uplift and orogeny ● rejuvenation The Structure of North America ● The North American cordillera ● uplift and orogeny ● rejuvenation ● crustal stretching

● Continental geology ● cratons ● orogens ● passive margins 2. Tectonic Provinces around the World ● Continental geology ● cratons ● orogens ● passive margins ● active margins

● Types of tectonic provinces ● shield ● platform ● continental basin around the World ● Types of tectonic provinces ● shield ● platform ● continental basin ● orogen ● extended crust

● Ages of tectonic provinces ● Archean ● Early Proterozoic around the World ● Ages of tectonic provinces ● Archean ● Early Proterozoic ● Middle Proterozoic ● Late Proterozoic ● Paleozoic ● Mesozoic and Cenozoic

Thought questions for this chapter Figure 10.8b shows more continental crust of Mesozoic-Cenozoic tectonic age than continental crust of any geologic period. Does this contradict the hypothesis that most of the continental crust was differentiated from the mantle in the first half of Earth’s history?

● Continental accretion ● accreted terrains ● exotic terrains 3. How Continents Grow ● Modes of growth ● Magmatic addition ● Continental accretion ● accreted terrains ● exotic terrains

Terrain accretion

Terrain accretion Spreading center (divergent boundary) Aleutian Trench Wrangellia Spreading center (divergent boundary) Subduction margin (convergent boundary) Cascadia Trench Transform fault N O R T H A M E R I C A San Andreas Fault Island arc Submarine deposits Ancient ocean floor Displaced continental fragments

Thought questions for this chapter How would you recognize an accreted terrain? How could you tell if it originated far away or nearby?

● Modification by plate collision ● Alpine-Himalayan orogeny 4. How Continents Are Modified ● Modification by plate collision ● Alpine-Himalayan orogeny ● Assembly of Pangaea ● The Wilson Cycle

Alpine-Himalayan Orogeny

Alpine-Himalayan Orogeny

Alpine-Himalayan Orogeny

Alpine-Himalayan Orogeny

Alpine-Himalayan Orogeny

Wilson Cycle

Geologic Time Scale of Events in the History of Earth’s Continents

● Modification by epeirogeny ● cooling and heating of lithosphere 4. How Continents Are Modified ● Modification by epeirogeny ● cooling and heating of lithosphere ● weight of accumulating sediments or glacial ice

Thought questions for this chapter How would you identify a region where active orogeny is taking place today? Give an example. Would you prefer to live on a planet with orogenies or without them? Why?

● granite-greenstone terrains 5. Origin of Cratons ● Archean cratons ● granite-greenstone terrains ● high-grade metamorphic terrains

Thought questions for this chapter Why are the ocean basins just about the right size to contain all the water on Earth’s surface?

● Structure of the craton ● continental crust ● cratonic keel 6. Deep Structure of the Continents ● Structure of the craton ● continental crust ● cratonic keel

Thought questions for this chapter What would happen at the surface if the cold keel beneath a craton suddenly heated up? How might this effect be related to the formation of the Colorado Plateau?

Key terms and concepts Accretion Active margin Craton Cratonic keel Accreted terrain Accretion Active margin Craton Cratonic keel Epeirogeny Glacial rebound Magmatic addition Orogen Orogeny Passive margin Rejuvenation Shield Tectonic age

Key terms and concepts Tectonic province Wilson cycle