1. PLATE TECTONICS:
“SLIP SLIDIN’ AWAY”

2. Most plates are located on the ocean floor
Plate Tectonic Theory states the outermost layer of Earth is composed of 9 to 15 large plates and numerous small ones
Most plates are located on the ocean floor

3. Cracked egg used as a Model for Earth’s
tectonic plates

4. Lithosphere composed of the crust and upper mantle forms the Earth’s tectonic plates
Asthenosphere composed of very hot, melted plastic-like material lies below the lithosphere
Giant plates drift around on the asthenosphere at a rate of 1 to 2 centimeters per year

5. Area of interaction between adjacent plates referred to
as the plate boundary
Three types of plate boundaries as determined by the type
of interaction occurring are: divergent, convergent and transform

6. DIVERGENT BOUNDARY Formed when two adjacent plates move apart
Causes molten rock to erupt to the surface and create new crust; seafloor spreading is a result of this process
Creates mid-ocean ridges such as the mid-Atlantic ridge (bottom of Atlantic Ocean)
Continues to form new rocks that move away from ridges, explaining how crust can move and supporting the theory of Continental Drift
Causes underwater volcanos, earthquakes and forms rifts such as the Great Rift Valley in Eastern Africa

7. CONVERGENT BOUNDARY CONTINENTAL-CONTINENTAL
Formed when two plates move together
Plates’ crust type determines geologic
activity at interaction point
Equally dense continental crust plates buckle and
are pushed upward, forming mountain ranges
Examples: Himalayas (still forming), Alps and Appalachians

8. CONVERGENT BOUNDARY CONTINENTAL - OCEANIC SUBDUCTION
Oceanic crust is denser but less thick than
continental crust
Oceanic crust collides with continental crust
Oceanic crust bends, slides under the
continental crust, goes down into the mantle:
this interaction is called subduction
Results in earthquakes, volcanos and
rock deformation
Examples: Cascade Range in the
Pacific Northwest and the Andes
in South America

9. TRANSFORM BOUNDARY OR TRANSFORM FAULT MARGIN
Formed when two plates slide past each other
Usually move in opposite directions but may move in the same direction at different speeds
Fault: a deep crack in the Earth’s surface
Transform boundary : where plates catch and grind but crust is not produced or destroyed
San Andreas Fault
Plates build tension along boundary and release it
with a burst of energy and motion, resulting in earthquakes
Most transform boundaries located on the ocean floor
Notable exception is San Andreas Fault Zone in California
which passes through two thirds of the state: it has
produced many earthquakes, including those in
San Francisco and Los Angeles

10. REVIEW OF THE THREE TYPES OF PLATE BOUNDARIES

11. WHAT’S ON YOUR PLATE???

12. COMPARE THE THREE LAYERS OF AN EGG
TO THE THREE MAIN LAYERS OF THE EARTH A B
EARTH C A B C

13. STRUCTURE OF THE EARTH
Three main layers of the Earth: Core (inner and outer), mantle (upper and lower) and crust
Inner core under extremely high pressure, solid state, very dense, composed mostly of iron
Outer core liquid state, composed mostly of iron
Mantle largest layer, composed of silicon, oxygen, magnesium and iron, divided into upper and lower divisions as determined by different seismic wave speeds
Crust outermost layer, varies in thickness from
more than 60 km to less than 5 km
Contains higher percentage of silicon and aluminum and
lower percentage of magnesium and iron than the mantle
Generally less dense than the mantle