Plate Interactions
Tectonic Plate
Theory
Definition of Plate Tectonics
Plate Tectonics is the
theory that Earth’s
lithosphere is broken into
about 20 plates that move
on top of the
asthenosphere.
Map of the Plates
Questions 1-3
Use the map to answer the following questions.
Put your answers on the back of the map.
1. What is the name of the plate that we live on?
2. About where on the plate is New York City (on
the edge, near the edge, in the middle)?
3. What cities in the United States are on the edge
of a plate?
The Plates Are Moving!
Evidence to Support Plate Tectonics
1. Puzzle-like fit of continents
Shape of Continents
The Plates Are Moving!
Evidence to Support Plate Tectonics
1. Puzzle-like fit of continents
2. Fossils of same species of plants and animals on
various continents, across oceans
Fossil Evidence
The Plates Are Moving!
Evidence to Support Plate Tectonics
1. Puzzle-like fit of continents
2. Fossils of same species of plants and animals on
various continents
3. Glacial grooves that match across continents
Glacial Grooves
The Plates Are Moving!
Evidence to Support Plate Tectonics
1. Puzzle-like fit of continents
2. Fossils of same species of plants and animals on
various continents
3. Glacial grooves that match across continents
4. Coal in cold climates
Coal in Antarctica
The Plates Are Moving!
Evidence to Support Plate Tectonics
1. Puzzle-like fit of continents
2. Fossils of same species of plants and animals on
various continents
3. Glacial grooves that match across continents
4. Coal in cold climates
5. Earthquake boundaries that match the tectonic
plate boundaries
Earthquakes
Looking at the boundaries of
earthquakes around the world…
http://www.iris.edu/seismon/
There is a lot in common to those
plate boundaries!!!
Questions 4-7
Use the map to answer the following questions. Put your
answers on the back of the map.
4. Between the west coast of the North American
plate and the northeastern part of the Pacific
plate, the plates are moving in what way?
5. What do we have a lot of in this part of the
world?
6. Between the African Plate and the South
American plate, the arrows show the plates
moving in what way?
7. What do you think might be occurring there?
More Evidence:
Seafloor Spreading
Visualization of SeaFloor
Spreading
http://www.classzone.com/books/earth_science/t
erc/content/visualizations/es0803/es0803page01
.cfm?chapter_no=visualization
Questions 8 -10
Use the map to answer the following questions.
Put your answers on the back of the map.
8. Between what two plates would seafloor
spreading be happening?
9. What does this do to the size of the ocean
floor?
10. What force makes the magma rise up through
cracks in the seafloor?
Types of Plate Boundaries
• Convergent (Coming Together)
• Divergent (Dividing Apart)
• Transform (Slipping Past)
Converge!
Diverge!
Transform!
Convergent Boundaries
• Definition: Two plates
move into one another
• Two Types of Convergent
Boundaries
1. Continent to Continent
2. Subduction Zone
Subduction Zone
Subduction Zone
Formation of Andes
Mountains
 Nazca plate is moving under South American
plate - this is called subduction
 Nazca plate is ocean crust and therefore more
dense, it sinks below the continental crust
Question 11: What is a subduction zone?
Continent-to-Continent Collisions
Continent-to-Continent
Collision….
Formation of Himalayas
 Indo-Australian plate moved into Eurasian plate
 Eurasian plate began to crumble up
 Over millions of years, Himalayas were built and
continue to grow today
Question 12: Why have geologists found fish fossils at
the top of the Himalayas?
Divergent Boundaries
• Definition - when
two plates move
apart
• Example: MidAtlantic Ridge
• Ocean floor is
growing as the
plates move apart
Transform Boundary
Ring of Fire
Hot Spots - Volcanoes in the
middle of plates