Earth’s
Sub-Surface Processes
CONTINENTAL DRIFT
The process by
which the
continents move
slowly across Earth’s
surface.
PLATE TECTONICS
The theory that pieces of the
Earth’s lithosphere, called
plates, move about slowly on
top of the asthenosphere.
ALFRED WEGENER
German scientist who first
introduced the theory
Kontinentalverschiebung...
AKA
CONTINETAL DRIFT
Recognized that South America and
Africa fit together like a puzzle
What’s the evidence????
• Similarities of coastlines of continents (fit
together like a puzzle)
• Discoveries and correlations of worldwide
distribution of plant and animal fossils
• Records of Earth’s ancient magnetism
captured in lava flows
What’s the evidence????
• Observations of the flow of heat from Earth’s
interior
• Studies of the nature and exploration of the
ocean floor
• Locations of volcanoes and records of
earthquakes
The evidence Wegener needed…
Seafloor Spreading:
The movement of the
ocean floor away from
either side of a mid-ocean
ridge
Creates NEW CRUST!!!
Mid-Ocean Ridges:
A system of undersea
mountain ranges that
wind around the earth
Subduction:
When one plate moves under another plate at a
plate boundary.
Why does this happen??
Oceanic crust is more dense
than continental crust, so
it is forced under the less
dense material
Zone of Subduction
Oceanic-oceanic crust
Oceanic-continental crust
Forms:
Volcanic Island Arcs
& Deep trenches
Understanding the Theory of Plate Tectonics
• The theory not only describes continental movement,
but also proposes an explanation of WHY and HOW
continents move.
• Tectonics is the study of the formation of features in the
Earth’s crust.
• The theory that pieces of the Earth’s lithosphere, called
plates, move about slowly on top of the asthenosphere.
Lithosphere
Crust
Mantle
Outer Core
Inner Core
CRUST: outer surface; can be oceanic or continental
LITHOSPHERE: rigid interior of crust
ASTHENOSPHERE: plastic upper mantle
MANTLE: molten rock
OUTER CORE: liquid iron nickel
INNER CORE: solid iron nickel
Solid rock that
slowly flows
(Like putty)
PLATE BOUNDARIES
Divergent
Pull away from each other
Convergent
Crash into each other
Transform Fault
Slide past each other
National Geographic video
Stress: Folding & Faults
Compression
Tension
Shearing
Tension
Rocks are pulled apart
Occurs at divergent
boundaries
Rocks become thinner
Compression
Crustal rocks are pressed
together
Occurs at convergent boundaries
Pushes rock higher up or deeper
down in the crust
Shearing
This stress pushes rocks in
opposite direction
Sheared rock bends,
breaks, and twists as they
slide past each other
Occurs at transform faults
Result of Stress
ANTICLINE: up-curved folds in layers of rock
SYNCLINE: down-curved folds in layers of rock
MONOCLINE: gently dipping bends in horizontal rock layers
Anticline
Syncline
Monocline
Result of Stress
If there is no movement on
either side of break…this is
a fracture.
When there is movement,
this is a fault
Normal fault Occur along divergent boundaries and the
hanging wall moves downward, relative to the footwall
Reverse fault Occurs along convergent boundaries and
the hanging wall moves upward, relative to the footwall
Strike-slip fault Occurs along transform fault boundaries
and the rock on either side of fault slides horizontally
Thrust fault special reverse fault where fault plane is
nearly horizontal (common in steep mountains)
This Type of
Creates this type of
PLATE BOUNDARY
STRESS
Place where two plates meet
Force acting on a rock to change its shape or volume.
CONVERGENT BOUNDARY
Two Plates Move Towards Each Other
That Stress, creates this type of
FAULT
Break in the crust, where rocks slip past each o
REVERSE FAULT
Hanging Wall forced UP the Footwal
COMPRESSION STRESS
Rock is Squeezed Together
DIVERGENT BOUNDARY
Two Plates Move Away From Each Other
NORMAL FAULT
Hanging Wall Slides DOWN the Footw
TENSION STRESS
Rock is Stretched Out
STRIKE ‘N’ SLIP FAULT
Hanging Wall Moves PARALLEL
(Left or Right) to the Footwall.
TRANSFORM BOUNDARY
Two Plates Move Parallel To Each Other
SHEARING STRESS
Rock is Pushed in Two Opposite Directions
http://youtu.be/ryrXAGY1dmE
Hawaii Hotspot
Seafloor spreading and Megathrust