What is ridge push?
As oceanic lithosphere moves away from mid-ocean ridges, it cools, thickens, and becomes denser. This causes the plate to sink gradually, creating a slight slope that gravity drives the plate down - aka ridge push
What is slab pull?
Slab pull occurs when a tectonic plate’s dense, cool segment sinks into the mantle, creating a downward force that drags the rest of the plate at destructive margins.
List me 3 types of plate margins
- Constructive (divergent) plate margins
- Destructive (convergent) plate margins
- Conservative plate margins
What is conservative plate margins
Two plates slide past each other, causing powerful shallow-focus earthquakes
What is constructive (divergent) plate margins?
Two plates move apart
What is destructive (convergent) plate margins?
Two plates collide
List me 2 types of divergence?
- In oceanic areas, sea floor spreading occurs on mid ocean ridges
- In continental areas, stretching and collapsing of the crust creates rift valleys
What is mid-ocean ridges (divergence landform)?
Oceanic divergence creates submarine mountain ridges that span thousands of km. Transform faults cut these ridges at right angles, causing friction and shallow-focus earthquakes. Ridges can rise up to 4000 m, and volcanic activity may build islands like Ascension Island.
What is rift valleys? (divergence landforms)
Valleys form when lithosphere stretches and fractures into parallel faults, making the land between collapse into deep valleys seperated by uplifted blocks called horsts (e.g. Great African Rift valley)
List me three types of convergence?
- Oceanic plate meeting continental plate (Peru-Chile trench)
- Two oceanic plate meets (Marina Trench)
- Two continental plate meets (Himalayas)
Describe oceanic plate meets continental plate (convergent)?
Oceanic plate subducts under the continental; its bending forms a deep ocean trench at collision. Convergence uplifts and folds the continental into mountains (e.g., Andes). Beyond 100km oceanic melting (Benioff zone). intermediate/deep earthquakes
Describe two oceanic plate meets?
When two oceanic plates collide, one is forced underneath, creating a deep ocean trench. Magma from the Benioff Zone then builds crescents of submarine volcanoes, eventually forming island arcs.
Describe two continental plate meets?
Continental plates are less dense than the underlying asthenosphere, so they don’t subduct. Instead, when they collide, they uplift and buckle into high fold mountains.
