Download Introduction to Plate Tectonics

Introduction to
Plate Tectonics
Review
• You have 5 minutes to draw an island from the side
view. I will draw on the board a starting point for
you and I would like you to finish the drawing.
Islands actually look like….this!
Review: Earth Layers
• Crust, mantle, outer core, inner core
• Made of rock: crust, mantle
• Made of metal: both cores
The Rock Layers
• Crust: solid, hard rock
• Very top of mantle: solid, hard rock
• Rest of upper mantle: soft, gooey, hot rock
Lithosphere & Asthenosphere
• In order to describe the motion of tectonic plates,
scientists divide the rock layers in a different way
• Lithosphere: ALL of the solid, hard rock
• (crust + very top of mantle)
• Asthenosphere: The gooey, slightly melted rock
• (rest of upper mantle)
Lithosphere & Asthenosphere
• So, the lithosphere is on top, and the
asthenosphere is underneath
• The lithosphere floats on top of the asthenosphere
Lithosphere
• Earth used to be completely molten
• As it cooled, the lithosphere formed
• BUT – the lithosphere cracked in several places (like
a cracked eggshell)
• So the lithosphere is actually made of several
massive (huge) chunks called tectonic plates
Lithosphere
• There are 2 types of crust
• Oceanic crust: the crust that holds the ocean
• Very thin, very dense (heavy) rock
• The newest rock - more is constantly being made
• Continental crust – make Earth’s continents
• Rock is much thicker and much older
Asthenosphere
• So, the chunks of tectonic plates float on top of the
asthenosphere
• The asthenosphere moves – how
• Remember CONVECTION CURRENTS?
• Heat from Earth’s core travels up through the
asthenosphere, causing up and down movement
Plate Movement
• So convection currents make the asthenosphere
move (it oozes and flows, like oatmeal)
• This also moves the tectonic plates, which are
floating on top of the asthenosphere