1. ~ 4.0 Ga. One of the first islands to form on the Earth. The picture shows a bright sunny day, but the atmosphere is likely to have been dark and smoggy. All land at this time was formed by volcanic activity, either from hot spots or subduction zones. Continents, even small ones, are still a distance in the future.

2. Evolutionary Rock Cycles 258

3. The Origins of Continents The Earth began with no continents... Just small, scattered, isolated volcanic arcs... 265

4. Early Growth of Continents... that grew with time, lots of time. About 2 billion years worth into larger continents. 265

5. Volcanic Arcs Evolve into Microcontinents 264

6. Numerous Collisions Over About Two Billion Years Build the Cores Of Modern Continents Small volcanoes and microcontinents, moving across the earth are bound to collide, and stick together to form even larger continents. It was this process that built the large continents we see today. Without it most land masses would be about the size of a state, or perhaps a few states, islands really, like living on Madagascar or New Zealand.

7. http://ace.acadiau.ca/science/geol/rraeside/quizzes/worldmap3p.htm We are so used to the world as it exists today that it can be hard to imagine anything else. For example, in the image below the continents stand out prominently (partly of course because they are brightly colored), and then there is the Pacific ocean. But, if we were to go back 3 to 4 billion years the world would not look like this. Instead it would have been covered mostly by ocean with small islands scattered here and there, like the ones circled below. Imagine a world where the biggest land masses are only the size of Fini, or New Zealand, or at best Borneo and New Guinea. Fiji New Zealand Hawaii Borneo New Guinea

8. United Plates of North America 261

9. Stage Four 2. 39 – 2.33 Stage One 4.0 – 3.0 Stage Two 2.7 – 2.5 Stage Three 2.7 – 2.5 Constructing The Heart Of the North America Continent Stage Five 1.8 – 1.7 Stage Six 1.8 – 1.6 262 & 266

10. All the continents grew by these processes. 261 North America at 1.6 billion years ago. Finally a solid core.

11. Supercontinent Cycles So, think about how such a planet works

12. Rodinia Supercontinent From about 1.2 billion to 600 million years ago 273

13. Pangaea Supercontinent From about 320 million to 175 million years ago 257

14. Cycles Within Cycles Within Cycles

15. Leading to the Earth as it Exists today