Evidence for Plate
Tectonics
Example Power Point
Earth Science
Standard:
Dynamic Earth Processes
• Students know features of the
ocean floor (magnetic patterns,
age, and sea-floor topography)
provide evidence of plate
tectonics
Vocabulary
• Transform faults: faults that run across a
mid-ocean ridge
• Mid-ocean ridges: undersea mountain
chain where new ocean floor is produced:
a constructive (divergent) plate boundary
Mid-ocean ridge
Vocabulary
• Ocean-floor spreading: process in
which old ocean floor is pushed away
from a mid-ocean ridge by the formation
of new ocean floor
• Trenches: V-shaped valley on the ocean
floor where old ocean floor is subducted;
a convergent plate boundary
Ocean Floor spreading
• Volcanic and
earthquake activity
occurs at the mid-ocean
ridges.
• As lava erupts and
hardens, ocean floor
moves away on either
side of the ridge
Deepest Parts of the Oceans
• As older ocean floor moves away from midocean ridges, it moves down deep into Earth
along trenches.
• Trenches are found close to continents or
near strings of islands such as Alaska’s
Aleutian Islands.
Magnetic Patterns
• Basalt rock on
the ocean floor
records the earths
magnetic field
when it hardens
• The pattern of
magnetic stripes
is identical on
both sides of a
mid-ocean ridge
Summary
• Ocean floor topography
– Underwater mountains - mid-ocean
ridges
– Deep underwater trenches
• Evidence
– Age of rock on ocean floor
– Magnetic patterns
– Ocean floor is spreading at mid-ocean
ridges
Quiz
1. Where is the youngest rock in the
ocean formed?
2. Where is the deepest part of the ocean?
3. Name three pieces of evidence that
supports plate tectonics?
Acknowledgement
• Books: Exploring Earth Science
– Prentice Hall
• Internet: www.usgs.gov
– Dynamic Earth