PLATE TECTONICS
Early Evidence for Plate Tectonics Evidence
- continental fit
- rock sequences
- glacial evidence
- fossil evidence
- polar wandering
Modern Evidence for Plate Tectonics
- seafloor spreading - 1960's
Types of Plate Boundaries
- Divergent Plate Boundaries
- Types of divergent boundaries
- Seafloor Spreading
- Intracontinental Rifts
- Features to look for
- seafloor plate separation
- Continental plate separation
- Types of rocks
- Convergent Plate Boundaries
- Types of convergent boundaries
- OC - OC
- plates collide and one is subducted
- sediments on the subducting plate are scrapped off
- at about 50 -100 km depth, the subducting plate melts
- the melted material rises and is erupted at volcanic arcs (andesitic magamas)
- OC - CC
- plates collide and OC is subducted beneath the CC
- sediments on the subducting plate are scrapped off
- the subducting plate melts and the material rises and erupts at volcanoes
- CC - CC convergence
- compressional forces cause faulting and thickening of crust - suture forms
- mountains form by compressional forces
- Features to look for
- island arcs
- deep sea trenches
- types of rocks
- OC - OC
- basaltic volcanism creates the volcanic arc islands
- OC - CC
- CC - CC
- mixture of OC - CC rocks and highly metamorphosed rocks
- Transform boundaries
- either OC or CC, move past each other
- Types of rocks
- rocks on either side of the boundary are of different age
Earthquakes as a result of plate tectonics