1. What are the layers of the earth (C.L.A.M.O.I.C) and their state of matter? 2. How many cm/year do you think your fingernails grow? T.S.W.B.A.T. understand the dynamic processes involved in the theory of plate tectonics.

Continents are moving as we speak!!! South America and Africa are moving away from each other at a rate of approximately 2-3 cm/year. South America and Africa are moving away from each other at a rate of approximately 2-3 cm/year. (This is about how fast your fingernails grow) The Hawaiian Islands are moving to the Northwest at a rate of 8-9 cm/year. The Hawaiian Islands are moving to the Northwest at a rate of 8-9 cm/year.

The Earth’s crust is divided into 12 major plates which are moved in various directions. The Earth’s crust is divided into 12 major plates which are moved in various directions. This plate motion causes them to collide, pull apart, or scrape against each other. This plate motion causes them to collide, pull apart, or scrape against each other. Each type of interaction causes a characteristic set of Earth structures or “tectonic” features. Each type of interaction causes a characteristic set of Earth structures or “tectonic” features. The word, tectonic, refers to the deformation of the crust as a consequence of plate interaction. The word, tectonic, refers to the deformation of the crust as a consequence of plate interaction.

World Plates

Continental Drift Wegener proposed that the continents floated somewhat like icebergs in water Wegener proposed that the continents floated somewhat like icebergs in water And that the continents had drifted apart And that the continents had drifted apart He did not know what caused the continents to drift apart He did not know what caused the continents to drift apart His theories were not widely accepted His theories were not widely accepted

Wegener’s Continental Drift Hypothesis Wegener suggested that 225 mya all of the land masses were connected in a supercontinent called Pangaea, a Greek word meaning ‘all lands’ Wegener suggested that 225 mya all of the land masses were connected in a supercontinent called Pangaea, a Greek word meaning ‘all lands’ Continents “Drifted” to present positions Continents “Drifted” to present positions Continents “Broke” through the ocean crust Continents “Broke” through the ocean crust

Continental Drift Alfred Wegener: Alfred Wegener: First to Proposed Hypothesis, 1915 First to Proposed Hypothesis, 1915 Published “The Origin of Continents and Oceans” Published “The Origin of Continents and Oceans” WHAT EVIDENCE DID HE USE TO PROPOSE HIS HYPOTHESIS!!! WHAT EVIDENCE DID HE USE TO PROPOSE HIS HYPOTHESIS!!!

Evidence Used by Wegener 1. Fit of South America and Africa 2. Fossils 3. Ancient Climates 4. Rock Structures

Alfred Wegener noted that Africa and South America appear to fit together neatly, like the pieces of a jigsaw puzzle Alfred Wegener noted that Africa and South America appear to fit together neatly, like the pieces of a jigsaw puzzle He proposed that the continents had been joined and had since drifted apart He proposed that the continents had been joined and had since drifted apart

Fossil remains in continuous bands across continents Fossil remains in continuous bands across continents Cynognathus - a land reptile from the Triassic period Cynognathus - a land reptile from the Triassic period

Wegener’s matching of mountain ranges on different continents Paleoclimatic evidence for Continental Drift

Main Objection to Continental Drift Theory Its inability to provide a mechanism for the movement of continents. Its inability to provide a mechanism for the movement of continents. How did the continents move? How did the continents move?

Harry Hess’ Discovery During WWII, Harry Hess was a During WWII, Harry Hess was a captain in the Navy on a transport ship. His vessel was equipped with an echo sounder (SONAR or sound waves bounced off ocean floor). Showed the topography of ocean floor was NOT flat. which Hess used to map the ocean floor to aid the war effort His vessel was equipped with an echo sounder (SONAR or sound waves bounced off ocean floor). Showed the topography of ocean floor was NOT flat. which Hess used to map the ocean floor to aid the war effort In the postwar period the Atlantic was extensively mapped and the Mid-Atlantic Ridge was discovered In the postwar period the Atlantic was extensively mapped and the Mid-Atlantic Ridge was discovered

Plate Tectonics – Initially proposed in 1960’s More encompassing than continental drift. More encompassing than continental drift. Theory that replaced the Continental drift theory. Theory that replaced the Continental drift theory. Provided a mechanism for movement Provided a mechanism for movement

Evidence for Plate Tectonics 1. Earthquake and Volcano “Belts” Pacific Ring of Fire Pacific Ring of Fire 2. Ocean Floor Topography 3. Mid Atlantic Ridge 4. Convection Currents 5. Seafloor Spreading 6. Paleomagnetism

Ring of Fire-All around the Pacific Ocean Geologists discovered that many of the Earth’s volcanoes and earthquakes occurred in a pattern, or set location Geologists discovered that many of the Earth’s volcanoes and earthquakes occurred in a pattern, or set location Called the Ring of Fire Called the Ring of Fire Temperature around the “ring” higher than in other places Temperature around the “ring” higher than in other places

Ocean Floor Has Mountain Ranges larger than those found on the surface

Mid-Atlantic Ridge A giant undersea mountain range extending north to south in the center of the Atlantic Ocean A giant undersea mountain range extending north to south in the center of the Atlantic Ocean Ocean sediments were discovered to be youngest near the ridge and oldest near the continental margins Ocean sediments were discovered to be youngest near the ridge and oldest near the continental margins

Plate Movement “Plates” of lithosphere are moved around by the underlying hot mantle convection cells “Plates” of lithosphere are moved around by the underlying hot mantle convection cells

Convection

Sea-Floor Spreading Hess’s theory that new ocean crust is formed at mid-ocean ridges and destroyed at subduction zones. Hess’s theory that new ocean crust is formed at mid-ocean ridges and destroyed at subduction zones.

PALEOMAGNETISM – another piece of evidence supporting Plate Tectonics Earths magnetic field will REVERSE over time. When this occurs…IRON-BEARING minerals will arrange themselves parallel to the Earth’s magnetic bearing. Essentially, rocks with metal minerals in them…act like little compasses…they point to North…Wherever North is at that time!!

Magnetometer – detects small changes in magnetic fields. Used to construct “magnetic maps” Magnetometer – detects small changes in magnetic fields. Used to construct “magnetic maps”

The Theory of Plate Tectonics a combination of two earlier ideas, continental drift and sea-floor spreading. a combination of two earlier ideas, continental drift and sea-floor spreading. According to the theory, the surface of the Earth is broken into large plates. According to the theory, the surface of the Earth is broken into large plates. The size and position of these plates change over time. The size and position of these plates change over time. The edges of these plates, where they move against each other, are sites of intense geologic activity, such as earthquakes, volcanoes, and mountain building The edges of these plates, where they move against each other, are sites of intense geologic activity, such as earthquakes, volcanoes, and mountain building

Map Of The Plate Boundaries