Plate Boundaries

Plate Tectonics ▪ Plate Tectonics – the theory that the Earth’s lithosphere is divided into tectonic plates that move around on top of the asthenosphere ▪ The lithosphere is made of two types of crust ▪ Continental – Less dense, Thicker on average ▪ Oceanic – More dense, Thinner on average

What Directions Do Plates Move? ▪ 3 types of plate boundaries 1. Convergent – Plates are moving towards each other 2. Divergent – Plates are moving away from each other 3. Transform – Plates are moving past each other

▪ Convergent – Plates are moving towards each other ▪ Subduction – subduction occurs when one tectonic plate is pushed underneath another ▪ DENSITY!! ▪ More dense plates will sink below less dense plates Convergent Plate Boundary

▪ Arrows – ▪ Picture – ▪ Land Features – Trenches, Island Arc, Underwater Volcanoes Oceanic-Oceanic

Ocean-Continent ▪ Arrows – ▪ Picture – ▪ Land Features – Very active volcanoes, Trench from subduction zone

Continent-Continent ▪ Arrows ▪ Picture ▪ Land Features – Mountain Ranges

Divergent Plate Boundary ▪ Divergent – Plates are moving away from each other ▪ Sea-floor Spreading – at divergent boundaries magma rises and cools, slowly pushing the plates apart ▪ Where the magma comes up is called an Oceanic Ridge

Transform Plate Boundary ▪ Transform – Plates are moving past each other ▪ Strike-Slip-Fault – Plates are moving past each other causing friction and earthquakes ▪ Famous Example – San Andreas Fault