Boundaries, Stresses, and Faults OH MY!

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Boundaries, Stresses,and FaultsOH MY!

• How do geologic events change and shape Earths
  surface?

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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

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Plates around Earth move in different directions
cause different geologic events (things that
happen on Earth).
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Lets 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).
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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

Lets break it down
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Divergent Boundaries

• Place where 2 plates pull away from each other

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How is the rock pulled at Divergent
Boundaries?Rock gets THIN in the middle as it
is pulled apart.This STRESS is called
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What happens when the rock SNAPS from the Stress
of Tension?A Normal Fault (fault is a break in
Earths crust)Rock drops down as it breaks
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What happens next _at_ Divergent Boundaries?

• A geologic feature or event
• May form RIFT VALLEYS on continents
• SEA-FLOOR SPREADING in the ocean

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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

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Transform Boundaries

• Place where 2 plates slide past each other

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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

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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.

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What happens next at Transform Boundaries?

• May cause Earthquakes when the rock snaps from
  the pressure.
• A famous fault _at_ a Transform Boundary is the San
  Andreas Fault in California.

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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!

San Andreas Fault, CA ?
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Convergent Boundaries

• Places where plates crash (or crunch) together or
  subduct (one sinks under)

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How is the rock pushed at convergent boundaries?

• Rock is pressed or squeezed together.
• This stress is called COMPRESSION

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What happens when the rock is squeezed from the
Stress of Compression?

• A REVERSE FAULT
• Rock is forced upward as it is squeezed.

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What happens next _at_ Convergent Boundaries?

• May form Mountain Ranges.
• These are Folded Mtns. Like the Himalayas or the
  Rockies.

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How Do Mountains Form?

• The forces of plate movement can build up Earth's
  surface, so over millions of years, movement of
  faults can change a perfectly flat plain into a
  gigantic mountain range
• Sometimes, a normal fault uplifts a block of
  rock, so a fault-block mountain forms
• When a piece of rock between two normal faults
  slips down, a valley is created

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Anticlines and Synclines  

• Describs downward and upward folds in rock
• An _______is a fold in a rock that arcs upward
• A _______ is a fold in a rock that arcs downward
• These folds in rocks are found on many parts of
  the earths surface where compression forces have
  folded the crust.

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What else happens _at_ Convergent Boundaries?

• May form Volcanoes _at_ Subduction Zones
  as denser oceanic plate dives under less dense
  continental plate.

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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 _at_ subduction zone.

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Plate Boundaries

• Can you match the boundary name correctly with
  its diagram?
• _____________
• _____________
• _____________

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Plate Boundaries

• Correct Answers
• Divergent
• Convergent
• Transform

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StandardS6E5. Students will investigate the
scientific view of how the earths surface is
formed.
d. Describe processes that change rocks and the
surface of the earth. 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?
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StandardS6E5. Students will investigate the
scientific view of how the earths surface is
formed

• e. Recognize that lithospheric plates constantly
  move and cause major geological events on the
  earths surface.
• Review
• 1. List the geologic event(s) that can occur at
  each plate boundary. (What happens or is formed
  here?)
• ____ ____ _at_ Divergent Boundaries
• ____ ____ _at_ Convergent Boundaries
• __________ _at_ Transform Boundaries

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StandardS6E5. Students will investigate the
scientific view of how the earths surface is
formed

• f. Explain the effects of physical processes
  (plate tectonics, erosion, deposition, volcanic
  eruption, gravity) on geological features
  including oceans (composition, currents, and
  tides).
• Review (Make sure to use voc. from your notes)
• Explain how Earthquakes occur.
• How can new ocean floor be created?
• How do mountain ranges form?
• Why is density important at subduction zones?