1. Theory of Plate Tectonics

2. What are Plate Tectonics
Earth is broken into large plates that change in their size and position
Float on the molten interior layer of Earth
Continents ride on the plates
Continents move at a rate of 1cm/year
Atlantic Ocean getting wider; Pacific Ocean getting narrower
Cause of earthquakes and volcanoes and forms mountains

4. Shape and Structure of Earth
Earth has 3 layers:
Core
Mantle
Crust
Each layer has unique chemical and physical characteristics
Earth is shaped as an “oblate spheroid”
Flattened poles; bulging equator

5. Shape and Structure of Earth
Core: divided into an inner core and outer core
Outer core is a liquid (molten) layer
Inner core is at the center of Earth; is a solid
Made of iron and nickel; °C
Mantle: layer below the crust
Divided into sublayers: upper mantle, asthenosphere (magma), lower mantle
Crust: outermost layer of the Earth
Made of solid rock
Lithosphere: made up of continental and oceanic plates; includes crust and upper mantle

7. Asthenosphere and convection Currents
Asthenosphere is the hotter upper mantle below lithosphere
Flows like silly putty but it’s not a liquid layer
Large temperature difference between upper mantle (1400 °C) and lower mantle (2600 °C)

8. Asthenosphere and Convection Currents
Difference in temperature creates convection currents
Convection current – transfer of heat in a liquid or gas that causes magma to rise
Rises up through the mantle and into the crust
Causes molten rock to move
Formation of oceanic ridges (seafloor spreading) and mid-ocean islands

10. Major Plates
Geologists have divided tectonic plates into three arbitrary categories:
Major plates: Pacific Plate, North American Plate, Eurasian Plate, African Plate, Antarctic Plate, Indo-Australian Plate, South American Plate
Minor/secondary plates: Somali Plate, Nazca Plate, Philippine Sea Plate, Arabian Plate, Caribbean Plate, Cocos Plate, Scotia Plate
Microplates

11. Major Plates

12. Plate Boundaries
Plates interact with each other at three types of boundaries:
Convergent
Divergent
Transform
Interactions between these plates results in geological features and activity

13. Convergent Boundary
Convergent boundary: two plates come together and push against one another
i.e. Boundary between South American plate and the Nacza plate
One plate rides up over the lithosphere of another plate, forming a subduction zone

14. Convergent Boundary
Results in the formation of mountain ranges and volcanoes (volcanic arcs)
Continental – Continental boundary: creation of large mountain ranges; both plates too light to subduct
Continental – Oceanic boundary: creation of volcanic arcs
Oceanic – Oceanic boundary: creation of island arcs and formation of deep trenches

15. Divergent Boundary
Divergent boundary: two plates move away from each other
Creates a gap of magma to form new crust between the two
i.e. Mid-Atlantic ridge; separation between South American and African plate

16. Divergent Boundary Oceanic Plates
Rising convection currents lift the lithosphere
Creates a fissure in the plate
Magma flows into the fissure, solidifies, and then repeats itself.
Continental Plates
Pulling apart of plates produces a rift
As rifts grow deeper dropping below sea level, water will enter
i.e. Red Sea

17. Transform Boundary
Transform boundary: two plates slide past one another
Results in strong earthquakes but no loss or gain of sea floor
i.e. Boundary between the Pacific plate and the North American plate