3 - Plate Tectonics

driving forces of plate tectonics

result of heat transfer and density differences in the mantle, hence this cartoon

what is conduction

heat transfer through direct contact, driven externally

what is convection

heat transfer driven by density differences

what is advection

horizontal movement

what is radiation

heat transfer by electromagnetic waves

three driving forces of plate motion

1. mantle convection

2. slab pull

3. ridge push

what is mantle convection

transport of mass (and heat) through the earth as a result of the initial heat

what drives motion in mantle convection

earth retaining heat from formation + radioactive decay

in the original mantle convection model, how were plate margins moving?

spreading ridges were upflow zones, convergent margins were downflow

what is a triple junction

where the boundaries of three tectonic plates meet

what is slab pull

subducting slab descends, P + T increase, metamorphose basalt —> dense eclogite

what is eclogite composed of

lots of garnet and cpx

which is more dense?: a subducting slab or the mantle

subducting slab

where does ridge push occur

at divergent margins

what happens during ridge push

thermal uplift or doming (asthenosphere)

what happens to the new crust that forms as ridge push occurs

it slides off the slope, pushing it away from the ridge

what three forces are at play during plate motion

F_rp = ridge push

F_su = force of suction from trench retreat

F_sp = slab pull force

what is trench suction and what does it cause

downward force of subduction, pulls overriding forward, causes subduction zone to retreat

causes “trench rollback”