Download What forms at a spreading zone?

Aim: How do the plates of the Earth
move?
Do Now:
Using the worksheet, “Plate Movement:
In out and Sideways”, answer the
following questions below.
- What forms at a spreading zone?
- What forms at a fracture zone?
- What three features form at a
convergence zone?
I. Causes of Plate Motion
Convection currents within the mantle
push and pull the plates (ESRT p.10)
• Convection occurs when warm material
rises and cool material sinks (DENSITY!)
II. Types of Plate Boundaries
1. Divergent boundaries form where
two plates move apart (spreading).
• Rift valleys are found at the
boundaries the divergent plates.
• Oceanic ridges
are found on
either side of the
rift valley.
• Seafloor spreading produces new
oceanic crust at divergent plate
boundaries
2. Convergent boundaries form where
two plates come together.
Which type of
crust sinks under
the other and
why?
• Oceanic crust sinks since it is more dense.
• Subduction zones are where one plate is
forced down into the mantle beneath a
second plate.
• trenches mark
the subduction
zones on the
surface.
Subduction zone
A. Oceanic Crust vs. Continental Crust
• Oceanic crust sinks beneath the continental.
• Continental Volcanoes form from the rising magma.
(example: Andes Mountains)
B. Oceanic Crust – Oceanic Crust
• One of the two plates sinks under the other.
• Volcanic Islands grow out of the ocean
(example: Aleutian Islands)
C. Continental Crust – Continental Crust
• The two plates collide and the continents being carried
are forced upward.
• Mountain ranges form from the uplift of these
continents (example: Himalayan Mountains)
3. Transform fault boundaries form
where two plates grind/slide past
each other.
• They move
parallel
• Faults and fractures
- cuts and cracks.
• Shallow earthquakes occur
San Andreas fault in California is an example of a
transform boundary
Boundary Type
Convergent
Divergent
Transform
Movement
Features
ESRT PAGE 5