Plate Tectonics
Liz LaRosa for use with my 5th Grade Science Class
http://www.middleschoolscience.com 2009
Earth’s Layers
1.Scientists
determined the inner
layers using seismic
waves.
2.Earth’s crust is
broken up into huge
tectonic plates
(lithosphere) that drift
atop the soft, puttylike underlying middle
mantle
(asthenosphere).
The lithosphere is
made up of crust and
upper mantle.
The Mantle
• Thickest layer
• Contains most of
the Earth’s mass
• Is denser than the
crust
Plate movement is caused by
convection currents in the
asthenosphere.
http://pubs.usgs.gov/gip/dynamic/unanswered.html
The Core
• Both inner and outer
core are made of hot
metals.
• The inner core is
solid.
• The outer core is
liquid.
Tectonic Plates
Plates can move in three
directions.
• Together- Convergent boundary
• Apart- Divergent boundary
• Past each other-Transform boundary
Different Types of Boundaries
http://pubs.usgs.gov/gip/dynamic/understanding.html
Continental-Continental collision
ex: Indian and Eurasian Plates result in nonvolcanic continental mountains-the Himalayan
Mountains
Sea Floor Spreading- Divergent
boundaries
Sea Floor Spreading
• Mid Ocean Ridges – underwater mountain
chains that run through the Earth’s Basins
• Magma rises to the surface and solidifies
and new crust forms
• Older Crust is pushed
farther away from the ridge
Divergent Boundary –
Arabian and African Plates
Divergent Boundary –
Iceland
http://pubs.usgs.gov/gip/dynamic/understanding.html
Convergent Boundary – Oceanic & Continental
This is called a Subduction Zone because the ocean plate is
sinking under the continental.
Denser
basalt
Less dense
granite
http://pubs.usgs.gov/gip/dynamic/understanding.html & http://www.geology.com
At subduction zones of continental
and oceanic crust there are many
volcanoes( a volcanic arc) and
trenches due to the more dense
ocean plate sinking.
Transform Boundary – San Andreas Fault
At this boundary, crust is neither created or
destroyed.Many earthquakes occur at all plate
boundaries.
www.geology.com