Tectonics Flashcards
What is the plate tectonic theory ?
The earths crust is made up of several rigid plates moving relative to one another
What is ridge-push ?
At mid-ocean ridge magma is risen up into the ridge causing a slope, gravity then acts upon the slope causing older and denser lithosphere to slide away.
What is slab-pull ?
Older and denser plate sub-ducted under less dense plate, edge of the plate sub-ducted as plate is cooler causing it to sink and drag the plate with it
What are convection currents ?
Liquid magma heated up near the core. then rises as hotter it gets more buoyant, then reaches lithosphere where it cools and dense, then as it gets cooler it horizontally spreads and sinks again dragging the plates with it.
What is a plate margin ?
Where two or more tectonic plates meet
Constructive plate margin ?
Where plates are moving apart.
Destructive plate margin ?
Where plates move towards each other.
Conservative plate margins ?
Plates slide past each other so relative movement is horizontal.
What happens at a destructive plate margin between continental and oceanic plates ?
The denser oceanic plate subduct below continental creating an ocean trench and chain of volcanoes.
What happens at a destructive plate margin between 2 oceanic plates ?
Heavier plate subduct into asthenosphere
What happens at a convergent plate boundary between 2 continental plates ?
2 plates collide and both have same density so prevents subduction and can cause fold mountains.
What happens at a constructive plate margin between 2 oceanic plates ?
Two plates moving apart, magma rises between the gap forming new land when cooled causing ocean ridge, sea floor spreading
What happens at a constructive plate margin between 2 continental plates ?
Two plates move apart any land in the middle partially collapses, causes rift valley and graben (valley itself).
What is a hotspot ?
Areas of the mantle have more radiogenic heat than others around it, because they are hotter magma is less dense so a plume rises peircing the crust and creating volcanic activity.
