- Earth's Magnetic Field has both a north and south pole
- We cannot feel earth's magnetic field
Cure Point- When iron-rich minerals are heated above temperature known as the cure point, the rocks lose their magnetism
- Iron-rich grains can cool down and return to having its magnetism
Fossil Magnetism- Rocks formed thousands or millions years ago have records of the direction of the magnetic poles
- Also known as paleomagnetism
- Rocks indicates lattitude at the time it became magnetized
Apparent Polar Wandering:
- Many peleiomegnetic poles once existed
- If magnetic poles remain stationary, their apparent movement is produced by continental drift
A Scientific Revolution Begins:
Oceanic Ridge System- Winds through all of the major oceans
- One of segments called Mid-Atlantic Ridge
- Discovery of central rift valley
- earthquake discovered occurring in trenches at sea floor
Thursday: 37-42 notes
Continental Drift: An Idea Before Its Time
- South America and Africa fit together like a puzzle piece
- Alfred Wegener set forth bas outline of his hypothesis of continental drift in his book The Origin of Continents and Oceans
Pangaea- A supercontinent that once existed
- Began to fragment into smaller continents during the Mesozoic era and drifted to their present positions
Fit of the Continents
- Wegener saw similarities of coastlines along the different continents
- Atlantic ocean was formed
Fossil Evidence
- Identical fossil organisms found in South America and Africa
Mesosaurus- aquatic fish-catching reptile
- Several fossil organisms found on different land masses
- During ice age the lowering of sea level allowed animals to cross the narrow Bering Strait between Asia and North America
Glossopteris- Plant, identified by its large seeds that were not easily distributed, was found widely among Africa, Australia, India, and South America
- Only grew in a subpolar climate
Present-day Organisms- Modern oganisms with similar ancestries clearly had to evolve in isolation during the las few tens of millions of years
Rock Type and Structural Similarities
- Similarties in rock structures on both sides of the Atlantic Ocean
- Linked land masses together
Paleoclimatic Evidence
- Dramatic global climatic changes druing the geologic past
- Layers of glacially transported sediments of the same age were found in southern Africa and South America
- Fossils from the coal fields indicate that the tree ferns that produced the coal deposits had large fronds, which are indicative of tropical settings
The Great Debate
- Wegener translated his book into English, French, Spanish, and Russian
- His hypothesis had a great deal of criticism
Rejection of the Continental Drift Hypothesis
- Gravitational force that the moon and sun exert on the earth to produce tides
- Wegener argued that the tidal forces would chiefly affect earth's outermost layer, which would slide as detached continental fragments over the interior
- Larger sturdier continents broke through the oceanic crust
- Wegener wrote 4th edition of his book
- Danish workers took measurements but found no evidence of drift
Monday: 50-60 notes
Plate Tectonics: The New Paradigm
Plate Tectonics- Theory of continental drifts and seafloor spreading united
- Mechanisms of subduction and seafloor spreading that turn earth's major features that include continents, mountains, and ocean basins
- Basis for viewing most geologic processes
Earth's Major Plates
Lithosphere- Uppermost mantle along the overlying curst
- Broken down into plates
- Are the thinest in the oceans where their thickness may vary from kilometers at the oceanic ridges to 100 kilometers in the ocean basins
- Overlies a weaker region in the mantle called asthenosphere
- Broken into numerous segments called lithoshperic or tectonic plates that are in motion to one another and continually changing in shpe and size
Asthenosphere- The temperature/pressure reginme in the upper part is such that rocks are very near their melting points
- A very weak zone that permits the lithosphere to be effectively detached from layers below
- Weak rock within upper part allows earth's rigid outer shell to move
Plate Boundaries
- Tectonic Plates move as coherent units relative to all other plates
- All interactions among individual plates occur along their boundaries
- Plates are bounded by three distinct types of boundaries
Divergent Boundaries- Where 2 plates move apart, resulting in upwelling of material from the mantle to create new seafloor
Convergent Boundaries- Where 2 plates move together, resulting in oceanic lithosphere descending beneath an overriding plate, eventually to be reabsorbed into the mantle, or possibly in the collision of two continental blocks to create a mountain system
Transform Fault Boundaries- Where 2 plates grind past each other without the production or destruction of lithosphere
- Each plate is bounded by a combination of these three types of plate margins
- Individual plates may diminish or grow in area depending on the imbalance between the growth rate at divergent boundaries and the rate at which the lithosphere is destroyed at convergent boundaries
- Plate boundaries are not fixed but move about
- New plate boundaries can be created in response to changes in the forces acting on the rigid slabs
Divergent Boundaries
- Are mostly located along the crests of oceanic ridges and can be thought of as constructive plate margins
- Also called spreading centers because the seafloor spreading occurs at these boundaries
Oceanic Ridges and Seafloor Spreading
- The mechanism that operates along the oceanic ridge system to create new seafloor is appropriately called seafloor spreading
- Reason for elevated position of the oceanic ridge is that newly created oceanic crust is hot, and occupies more volume, which makes it less dense than cooler rocks
Continental Drifting
- Divergent plate boundaries can develop withing a continent, the landmass can split into two or more smaller segments
- The splitting of a continent is called continental drift
Earth's Magnetic Field and Fossil Magnetism:
- Earth's Magnetic Field has both a north and south pole
- We cannot feel earth's magnetic field
Cure Point- When iron-rich minerals are heated above temperature known as the cure point, the rocks lose their magnetism
- Iron-rich grains can cool down and return to having its magnetism
Fossil Magnetism- Rocks formed thousands or millions years ago have records of the direction of the magnetic poles
- Also known as paleomagnetism
- Rocks indicates lattitude at the time it became magnetized
Apparent Polar Wandering:
- Many peleiomegnetic poles once existed
- If magnetic poles remain stationary, their apparent movement is produced by continental drift
A Scientific Revolution Begins:
Oceanic Ridge System- Winds through all of the major oceans
- One of segments called Mid-Atlantic Ridge
- Discovery of central rift valley
- earthquake discovered occurring in trenches at sea floor
Thursday: 37-42 notes
Continental Drift: An Idea Before Its Time
- South America and Africa fit together like a puzzle piece
- Alfred Wegener set forth bas outline of his hypothesis of continental drift in his book The Origin of Continents and Oceans
Pangaea- A supercontinent that once existed
- Began to fragment into smaller continents during the Mesozoic era and drifted to their present positions
Fit of the Continents
- Wegener saw similarities of coastlines along the different continents
- Atlantic ocean was formed
Fossil Evidence
- Identical fossil organisms found in South America and Africa
Mesosaurus- aquatic fish-catching reptile
- Several fossil organisms found on different land masses
- During ice age the lowering of sea level allowed animals to cross the narrow Bering Strait between Asia and North America
Glossopteris- Plant, identified by its large seeds that were not easily distributed, was found widely among Africa, Australia, India, and South America
- Only grew in a subpolar climate
Present-day Organisms- Modern oganisms with similar ancestries clearly had to evolve in isolation during the las few tens of millions of years
Rock Type and Structural Similarities
- Similarties in rock structures on both sides of the Atlantic Ocean
- Linked land masses together
Paleoclimatic Evidence
- Dramatic global climatic changes druing the geologic past
- Layers of glacially transported sediments of the same age were found in southern Africa and South America
- Fossils from the coal fields indicate that the tree ferns that produced the coal deposits had large fronds, which are indicative of tropical settings
The Great Debate
- Wegener translated his book into English, French, Spanish, and Russian
- His hypothesis had a great deal of criticism
Rejection of the Continental Drift Hypothesis
- Gravitational force that the moon and sun exert on the earth to produce tides
- Wegener argued that the tidal forces would chiefly affect earth's outermost layer, which would slide as detached continental fragments over the interior
- Larger sturdier continents broke through the oceanic crust
- Wegener wrote 4th edition of his book
- Danish workers took measurements but found no evidence of drift
Monday: 50-60 notes
Plate Tectonics: The New Paradigm
Plate Tectonics- Theory of continental drifts and seafloor spreading united
- Mechanisms of subduction and seafloor spreading that turn earth's major features that include continents, mountains, and ocean basins
- Basis for viewing most geologic processes
Earth's Major Plates
Lithosphere- Uppermost mantle along the overlying curst
- Broken down into plates
- Are the thinest in the oceans where their thickness may vary from kilometers at the oceanic ridges to 100 kilometers in the ocean basins
- Overlies a weaker region in the mantle called asthenosphere
- Broken into numerous segments called lithoshperic or tectonic plates that are in motion to one another and continually changing in shpe and size
Asthenosphere- The temperature/pressure reginme in the upper part is such that rocks are very near their melting points
- A very weak zone that permits the lithosphere to be effectively detached from layers below
- Weak rock within upper part allows earth's rigid outer shell to move
Plate Boundaries
- Tectonic Plates move as coherent units relative to all other plates
- All interactions among individual plates occur along their boundaries
- Plates are bounded by three distinct types of boundaries
Divergent Boundaries- Where 2 plates move apart, resulting in upwelling of material from the mantle to create new seafloor
Convergent Boundaries- Where 2 plates move together, resulting in oceanic lithosphere descending beneath an overriding plate, eventually to be reabsorbed into the mantle, or possibly in the collision of two continental blocks to create a mountain system
Transform Fault Boundaries- Where 2 plates grind past each other without the production or destruction of lithosphere
- Each plate is bounded by a combination of these three types of plate margins
- Individual plates may diminish or grow in area depending on the imbalance between the growth rate at divergent boundaries and the rate at which the lithosphere is destroyed at convergent boundaries
- Plate boundaries are not fixed but move about
- New plate boundaries can be created in response to changes in the forces acting on the rigid slabs
Divergent Boundaries
- Are mostly located along the crests of oceanic ridges and can be thought of as constructive plate margins
- Also called spreading centers because the seafloor spreading occurs at these boundaries
Oceanic Ridges and Seafloor Spreading
- The mechanism that operates along the oceanic ridge system to create new seafloor is appropriately called seafloor spreading
- Reason for elevated position of the oceanic ridge is that newly created oceanic crust is hot, and occupies more volume, which makes it less dense than cooler rocks
Continental Drifting
- Divergent plate boundaries can develop withing a continent, the landmass can split into two or more smaller segments
- The splitting of a continent is called continental drift