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

PANGEA

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.

Crust Lithosphere 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 DivergentConvergentTransform Fault Pull away from each otherCrash into each otherSlide past each other

Divergence Convergence

Convergence

Transform Fault: San Andreas Fault

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)

Hawaii Hotspot Hawaii Hotspot Seafloor spreading and Megathrust