Download Planet Earth - Sonoma Valley High School

Plate tectonics :
chapter 9.3 & 9.4
Temperature



In core, 6000+ C
Radioactive
elements, high
pressure create
the high temps
Convection
currents in the
mantle move the
continents
Convection currents




Convection currents occur when a gas or a liquid is heated
from the bottom.
Warm gasses & liquids are less dense than cold.
The warm substance rises and the cold sinks.
This process is responsible for air, ocean, & mantel currents.
Pair share: look
at the picture are
the two oceanic
plates moving
towards or away
from each
other?
Plates move as they ‘float’ on a moving mantle
Lithosphere
&
Asthenosphere



Made of the crust and the upper mantle- 60 miles thick
Divided into 7 large tectonic plates
Continental drift is the movement of the plates over
time
Plate
boundaries
Pair share: show
your partner
with your hands
how divergent
plates move.
•
•
Divergent : plates move apart
Magma comes up to fill the gap:
volcanoes, rift valleys, new crust formed
Mid-Atlantic ridge: a divergent plate boundary
N and S America were separated from Europe, Africa
Convergent
boundary
Pair share: show
your partner
with your hands
how convergent
plates move.
Plates move towards each other
 subduction when the denser oceanic plate dives below the
continental plate.
 Forms ocean trenches, mountain ranges, and volcanoes.
ex: Andes, Cascades mtns.

Colliding continental crusts
Mt. Everest



Both plates push upwards
Indian plate smashes into the Asian plate
Himalayas form: world’s tallest mountains
Transform faults



2 plates slide past
each other.
Pacific Plate slides
N past the North
American plate
San Andreas fault
Pair share: show
your partner
with your hands
how transform
faults move.
Review
1. Convection currents
occur because warm
liquids are _________
than cold liquids.
2. Divergent plates move
________ ______
each other.
3. Convergent plates
move ______ _____
each other.