6Evidence for Wegener’s Idea Continents fit together like puzzle piecesFossils found on different continents were identical…separated by thousands of miles…how’dey do dat?
7This is a freshwater reptile called a Mesosaurus This is a freshwater reptile called a Mesosaurus. Look at the distribution of fossils….hmmmmWegener compiled information about fossil discoveries from around the world. He felt this evidence was compelling.
9Evidence for Wegener’s Idea Continents fit together like puzzle piecesFossils found on different continents were identical…separated by thousands of miles…how’dey do dat?Dey ustabe neighbors
10Evidence for Wegener’s Idea Continents fit together like puzzle piecesFossils found on different continents were identical…separated by thousands of milesEvidence from Glaciers: Marks in bedrock left behind by glaciers located on AFRICA, SOUTH AMERICA, INDIA, and AUSTRALIA indicate that portions of these continents must have been CONNECTED in polar regions far from their present positions.
14Continental Drift Hypothesis The continents were all connected at one timeSupercontinent was called PangaeaPangaea broke apart up into two continents call Laurasia and GondwanalandContinents are still moving today
15…plus, he was “only” a climatologist Few believed Wegener…..…because he could not explain what hidden mechanism might be responsible for the movement of an entire continent!!!…plus, he was “only” a climatologist
161930Wegener leaves for Greenland to seek more evidence to test his hypothesis.He is never seen again. Some speculate that he ate his own dogs before he froze to death.The last photo him…His hypothesis is “hotly” debated for the next 30 years
23Evidence for plate tectonics So, how would you characterize the distribution of earthquakes and volcanoes around the world?Random?Patterned?Isolated?
24Evidence for plate tectonics Location of earthquakes and volcanoesThe distribution of earthquakes and volcanoes is not random. Earthquakes and Volcanoes occur TOGETHER in narrow bands under the oceans and along the edges of some continents.
25Evidence for plate tectonics …turns out…these locations are the edges of plates called “Plate Boundaries” where the plates rub against each other.
26VolcanoesVolcanoes are evidence of HEAT escaping from inside the EarthThis HEAT leaves the Earth as hot LAVASo…if heat from inside the Earth is making it all the way to the surface…MAYBE this movement of heat can move continents too
27What Makes the Plates Move What Makes the Plates Move? A concept in Science that Wegener KNEW, but did not imagine it could move continents.The plates move due to the transfer of HEAT energy from the Earth’s coreHeat leftover from Earth’s formation and produced by radioactive decay creates DENSITY differences in the mantle.This causes the fluid mantle to flow.The flow of mantle material pulls on the crust above it…like a leaf on a stream
30The of Plate Tectonics Evidence: THEORYThe of Plate Tectonics Evidence:Convection currents in the mantle move the plates around…and have been doing so for more than 4 billion years (1:10)Convection cell movement causes plates to collide, rip apart, and plunge back into the mantle
31We’re not sure which model is correct. This current model (A) predicts that convection cells are limited to the outermost plastic mantle.This current model (B) predicts that convection cells extend through the mantle toward the Lehmann discontinuity.We’re not sure which model is correct.Don’t you just LOVE theuncertainty of Science?
32Which model has the New York State Ed Dept selected for you?
33Current Scientific Theory “Plate Tectonics” The Earth’s crust is composed of about 22 platesThe plates are rigid and may contain CONTINENTAL or OCEANIC crust, or BOTHCONTINENTAL CRUST is mostly GraniteOCEANIC CRUST is mostly Basalt
35Evidence cont’d 2. Age of seafloor Oceanic igneous rock is much younger than continental igneous rocksOceanic rock gets younger as you approach the mid-ocean ridge (mountain range which runs through all world’s oceans)
37Reading PassagePlease open your text book to page 337 and read the passage titled “Seafloor Spreading” to the end of 339
38Magnetic pattern in rocks Earth’s magnetic pole reversesMagnetic crystals line up with earth’s poles when the magma hardensPatterns in ocean rocks show parallel strips on either side of the ridge that match in width, age, distance from the ridge, and magnetic polarity
80Theory of Plate tectonics So by the mid-60’s all the evidence came together to form theTheory of Plate tectonicsThis theory states that the Earth crust is broken into a series of plates which are constantly on the move.
81Convection computer model. The most current understanding.