How and Why the Plates Move Part II

1. Convection How and Why the Plates MovePart II

2. Convection currents in the mantle move the plates!

3. Convection currents cause : • The plates to pull apart which leads to sea floor spreading (ridge push) • The plates to collide which leads to subduction (slab pull)

4. Plate boundaries • A plate boundary is the area where two different plates come together • There are 3 main types of plate boundaries 1. Convergent = where plates crash into one another 2. Divergent = where the plates move away from each other (they separate) 3. Transform = where the plates slide past each other

5. Convergent Boundaries There are 3 types of convergent boundaries 1. continental/oceanic –forms trenches, volcanoes, earthquakes 2. oceanic/oceanic – forms trenches, volcanoes, tsunamis and earthquakes 3. continental/continental – forms mountains

6. The Mariana Trench – ocean/ocean • The Mariana trench is 2500 km long and 11,033 meters below sea level. • This trench is located where the pacific plate is subducted beneath the Philippine plate

7. Divergent Boundaries • Where two plates move away from one another • Sea floor spreading • Forms mid ocean ridges • New oceanic lithosphere forms • Mostly found in the ocean, but can be found on the continents

8. Mid Atlantic Ridge

9. Transform Boundaries • When two plates slide past each other horizontally • Sometimes called “faults” • Responsible for many earthquakes because when the plates slide past one another it is not a smooth ride! • Do not typically form volcanoes!

10. San Andreas Fault • Located in southern California • Site of many earthquakes

11. San Andreas Fault

12. Measuring Plate Movement • Scientists use many satellites in space to track plate movement • This group of satellites communicates with ground stations and is called a “global positioning system” or GPS for short. • Plates move on average of 2.5 cm per year

13. GPS