Plate Tectonics THE BASICS Tectonic Plates Rigid slabs

Plate Tectonics THE BASICS

Tectonic Plates Rigid slabs of rock, or plates, that move with respect to each other Large pieces of lithosphere Lithosphere – the cold and rigid outermost rock layer Below the lithosphere is the asthenosphere Asthenosphere – enables the plates to move because this layer is so hot it behaves like a plastic material; can flow

Plate Boundaries Exist where plates meet Divergent Where two plates separate Transform Where two plates slide past each other Convergent Where two plates collide

Convection Currents The circulation of material caused by differences in temperature and density The reason behind plate movement

Mapping Ocean Floor Late 1940’s – began exploring ocean floor Used an echosounder (SONAR) to measure ocean depths Used readings to create topographic maps Noticed vast mountain ranges stretching many miles in the middle of oceans Named them mid-ocean ridges

Seafloor Spreading Process by which new oceanic crust forms along a mid-ocean ridge and older oceanic crust moves away from the ridge

Evidence Magnetic Reversals Studied the magnetic signature of the minerals in these basalts and noticed they periodically flipped