Download Boundaries, Stresses, and Faults OH MY!

Boundaries,
Stresses,
and Faults
OH MY!
How do geologic events change and
shape Earth’s surface?
Remember…
The Lithosphere is made of…
The CRUST + The Upper Rigid Mantle
Plates may be called by different names:
Crustal Plates
Lithospheric Plates
Tectonic Plates
Plates around Earth move
in different directions & cause different
geologic events (things that happen on Earth).
Let’s recall what makes the plates move…
Convection Currents in the mantle move the plates as the core
heats the slowly-flowing asthenosphere (the elastic/plastic-like
part of the mantle).
There are 3 types of Plate
Boundaries.
Each one has a type of STRESS on
the rock
& a way that it breaks, called a
FAULT:
• Divergent Boundaries
• Convergent Boundaries
• Transform Boundaries
Let’s
break it
down…
Divergent Boundaries
• Place where 2 plates pull away from each other
How is the rock pulled at Divergent
Boundaries?
Rock gets THIN in the middle as it is
pulled apart.
This STRESS is called
What happens when the rock
SNAPS from the Stress of
Tension?
A Normal Fault (fault is a break in Earth’s
crust)
Rock drops down as it breaks
What happens next at Divergent Boundaries?
• A geologic feature or
event…
May form RIFT
VALLEYS on
continents
SEA-FLOOR
SPREADING in the
ocean
Helpful Hints…
• Divergent is like “dissecting” or “dividing”
• If you pull warm bubble gum or silly putty, it will
thin in the middle until it is stressed so much
that it breaks.
• Happens on land
& under H2O
Convergent Boundaries
• Places
where
plates crash
(or crunch)
together or
subduct (one
sinks under)
How is the rock pushed at convergent
boundaries?
• Rock is pressed or squeezed together.
• This stress is called COMPRESSION
What happens when the rock is squeezed
from the Stress of Compression?
• A REVERSE FAULT
• Rock is forced upward as it is squeezed.
What happens next at Convergent Boundaries?
• May form Mountain Ranges.
These are Folded Mtns. Like the Himalayas or the
Rockies.
What else happens at Convergent Boundaries?
• May form
Volcanoes @
Subduction
Zones
as denser
oceanic plate
dives under less
dense
continental
plate.
Helpful Hints…
• Convergent = “Connecting” boundaries
• May work like a trash compactor smashing
rock.
– Rock goes crunches up to make folded mountains.
– Rock goes down “under” @ subduction zone.
Transform Boundaries
• Place where 2 plates slide past each other
How is the rock broken at
Transform Boundaries?
• Rock is pushed in
two opposite
directions (or
sideways, but no
rock is lost)
• This stress is
called SHEARING
What happens when the rock is sheared
(or “cut”) from the Stress of Shearing?
• A STRIKE-SLIP FAULT
• Rocks on each side of the fault slip past
each other as they break.
What happens next at Transform Boundaries?
• May cause
Earthquakes
when the rock
snaps from the
pressure.
• A famous fault @ a
Transform
Boundary is the
San Andreas
Fault in
California.
Helpful Hints…
• Shearing means cutting (“Shears” are like
scissors)
• Transform boundaries run like trains going past
each other in different directions & they shake
the ground!
→
Plate Boundaries:
Can you match the
boundary name
correctly with its
diagram?
Standard:
S6E5. Students will investigate the scientific view of
how the earth’s surface is formed.
Review: (Make sure you use voc. from your notes)
1. How does the process of subduction recycle rock?
2. How can magma rise up on the ocean floor?
3. What happens to rock to form folded mountain
ranges?
Standard:
S6E5. Students will investigate the scientific
view of how the earth’s surface is formed
Review:
List the geologic event(s) that can occur at each
plate boundary. (What happens or is formed here?)
4. ____ & ____ @ Divergent Boundaries
5. ____ & ____ @ Convergent Boundaries
6. __________ @ Transform Boundaries
Standard:
S6E5. Students will investigate the scientific
view of how the earth’s surface is formed
Review: (Make sure to use voc. from your notes)
7. Explain how Earthquakes occur.
8. How can new ocean floor be created?
9. How do mountain ranges form?
10. Why is density important at subduction zones?