- No subduction or abduction
- Plates try ot move laterally past each other
- Most infamous are the San Andreas Fault in the USA and the North Antolian Fault in Istanbul [both are overdue a huge earthquake!]
- No volcanism
- Generates massive earthquakes
- These are not boundaries, as such, but rather a surface representation of surface plumes
- Plates do not always split above mantle plumes, but as the plate moves over the magma source, it generates a chain of islands
- The oreintation of the island gives an indication of the direction of the plate movement relative to the plume
= Chain of islands, connected to the Emperor Seamount chain (submerged)
= The islands become progressively older to the northwest, indicating the plate is moving in this direction
= This was anticipated before the discovery of continental drift as the islands become shallower in gradient, more advanced vegetation succession and have deeper soils to the northwest.
- Yellowstone Caldera is probably the niggest and highest risk
- Iceland is unusual being a large plume underneath a divergent boundary
This mantle plume theory is stil hotly debated and poorly understood - it is one of the few remaining mysteries of tectonic theory, which is otherwise now widely accepted.
Divergent and convergent boundary notes are on the way!