The Theory of Plate Tectonics

The Theory of Plate Tectonics Pieces of Earth’s lithosphere (plates) are in constant, slow motion, driven by convection currents in the mantle.

The Theory of Plate Tectonics Combines what geologists knew about sea-floor spreading, Earth’s plates, and continental drift into a single theory. +

Key Points The lithosphere is broken into separate sections called plates.

Key Points The plates float on top of the asthenosphere. CRUST Rigid Mantle

Key Points Movement of convection currents cause plates to move.

Read, “How Plates Move” on page 159

The Mosh Pit we call Earth’s Surface No plate can budge without affecting the other plates surrounding it. As the plates move, they collide, pull apart, or grind past each other. Causes changes in Earth’s surface (volcanoes, mountain ranges, deep-sea trenches)

Speaking of Mosh Pit Analogies… You can think of plate movements like crowd surfing. where are the convection currents…and where is the lithospheric plate?

Plate Boundaries Are where the edges of different plates meet. 3 Types of plate boundaries:

Sliding Boundaries Where two plates slip past each other, moving in opposite directions. Produces: earthquakes Example – The San Andreas Fault

Read, “Sliding boundary” on page 161

Spreading Boundaries Where two plates move apart. Produces: eruptions of molten material, new crust + earthquakes Examples – mid-ocean ridge & the Great Rift Valley in East Africa

Read, “Spreading Boundary” on page 160

Colliding Boundaries Where two plates come together. Produces: volcanoes or mountain ranges, + earthquakes Examples – Himalayas (India) & Aleutian Islands (Alaska)

Colliding Boundaries Density determines which plate will come out on top.

Read, “Colliding Boundary” on page 161

Draw a picture & write examples Tree Map Plate Boundaries Write Type of boundary Write definition Draw a picture & write examples