Mud pots and hot springs along the San Andreas Fault in California reveal new insights about the fault's structure and movement. Geologists have discovered that the fault is not a single clean fracture but is a complex network of smaller intersecting faults that split and rejoin. This finding helps explain why earthquake activity is broader than previously thought, with seismicity occurring miles away from the primary fault strand. It also suggests that stresses can build up over a wider area prior to a large earthquake on the fault.

1. http://www.newscientist.com/articleimages/dn14422/1-mud-springs-reveal-true-extent-of-san-andreas-fault.html

2. The link?

3. What happens at the battleground at plate boundaries?

4. Key Terms Fault: Continental drift: Subduction Zone: Convergent: Divergent: Transform: Continental Crust: Oceanic Crust:

5. What happens when the plates meet? Type of Margin Description of Changes Earthquake / Volcanic activity Examples Convergent (oceanic and continental) Convergent (two continental) Divergent on Land Divergent under the Ocean Transform

6. Convergent (Oceanic & Continental) Oceanic crust is denser than continental crust and so subducts (is forced to sink into the mantle) This is a subduction zone The sinking crust melts under friction & pressure…forms magma which creates volcanoes in the continental crust surface E.g. The Nazca plate in South America – forms the Andes & a line of volcanoes

7. Convergent: Oceanic & Continental

8. Convergent (Two Continental)

9. Convergent (Two continental) If both plates are continental, then they are both too light to really subduct So, a collision occurs Forms large mountain chains e.g. the Himalaya

10. Divergent on land

15. Divergent (on land) A.K.A. ‘constructive’ boundary As plates diverge, this allows magma to the surface When crusts diverge on land, it forms a rift valley e.g. Mid-Atlantic rift in Iceland, East African Rift

16. Divergent under the ocean When plates diverge under the ocean, magma rises to the surface to create new land The Mid-Atlantic Ridge is the biggest area of divergence As magma rises it cools, forming ridges of mountains / volcanoes and new land This is part of the recycling of oceanic crust

17. Divergent under the ocean In Iceland, the Mid-Atlantic ridge is diverging and splitting the country apart Iceland is growing every year!

18. Transform Where plates slide past each other No real surface features Creates a lot of earthquakes as friction builds up then one plate jumps forward E.g. San Andreas Fault, California, USA

19. Transform fault

20. Hotspots Weak areas in the earth’s crust that are far from plate boundaries that allow magma to punch through to the surface E.g. Hawaii