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

Forms: Volcanic Island Arcs & Deep trenches Oceanic-oceanic crust Oceanic-continental crust

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.

Crust Outer Core Inner Core Lithosphere Mantle

CRUST: outer surface; can be oceanic or continental LITHOSPHERE: rigid interior of crust ASTHENOSPHERE: plastic upper mantle MANTLE: molten rock

Solid rock that slowly flows (Like putty)

OUTER CORE: liquid iron nickel INNER CORE: solid iron nickel

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

PLATE BOUNDARY

Place where two plates meet

CONVERGENT BOUNDARY

Two Plates Move

Towards

Each Other

DIVERGENT BOUNDARY

Two Plates Move

Away

From Each Other

TRANSFORM BOUNDARY

Two Plates Move

Parallel

To Each Other Creates this type of

STRESS

Force acting on a rock to change its shape or volume.

COMPRESSION STRESS

Rock is

Squeezed

Together

TENSION STRESS

Rock is

Stretched

Out

SHEARING STRESS

Rock is Pushed in Two Opposite Directions That Stress, creates this type of

FAULT

Break in the crust, where rocks slip past each other

REVERSE FAULT

Hanging Wall forced

UP

the Footwall

NORMAL FAULT

Hanging Wall Slides

DOWN

the Footwall

STRIKE ‘N’ SLIP FAULT

Hanging Wall Moves

PARALLEL

(Left or Right) to the Footwall.

http://youtu.be/ryrXAGY1dmE

Hawaii Hotspot

Seafloor spreading and Megathrust