Continental Drift and the Origin of Plate Tectonics

The Theory of Plate Tectonics The Earth’s lithosphere is made of a number of solid pieces, called __________ which move in relation to each other. Tectonic plates

Alfred Wegener Theory of Continental Drift Proposed by __________ __________ in 1915. It stated that the earth’s continents separated and collided as they have moved over the surface of the Earth for millions of years. Alfred Wegener

Geographer and Polar Explorer Alfred Wegener (1880-1930) Geographer and Polar Explorer

Wegener’s Map showing the breakup of Pangea (Pangea song) See Reference Table Page 9

Future Super Continents

Africa S.America B. Wegener’s evidence for his his theory: 1. When you line up __________ and ___________________ they fit like a puzzle. Africa S.America

Fossil 2. __________ species have been found on widely separated parts of the earth.

3. Permian fossils are very similar in widely separated continents

Cynognathus

Lystrosaurus

Mt. Sirus Antarctica Lystrosaurus beds

Mesosaurus

S. America Africa fault fold 3. _____________ and ______________ have a good match of ancient continental rocks and tectonic _________ and _________ structures. fault fold

continent 4. Some mountain chains appear to be continuous from ____________ to___________ continent Ex: Appalachians & Caledonian

5. Evidence of _________ climates different from today ancient 5. Evidence of _________ climates different from today Finding coal beds which indicate tropical climates Ex.

Technology developed during Seafloor spreading Video Sonar - image the deep ocean using reflected sound. Magnetometer - detect faint magnetic fields. Developed to search for U-boats

Mid-ocean ridge

II. Sea Floor Spreading: Further evidence of horizontal movement of earth’s crust: A. The ocean floor has a system of submerged mountain ranges called ______________________ Mid-Ocean Ridges

Harry Hess Geologist at Princeton U. 1962 publishes “geopoetry.” Sea floor spreading hypothesis. Suggested that the ocean floor itself might be moving. Harry Hess

Material from deep within the earth comes to the surface at the ___________________ where it spreads apart to make ________________. Ocean ridges New ocean crust

B. The two major pieces of evidence are: 1. Age of igneous ocean material

Rocks of the ocean basins are _________ than continental rocks. younger

2. Reversal of magnetic polarity

When the rock hardened it kept the alignment forming a permanent record of the ___________________ of the earth at that time. Magnetic field

N S

N S

S Magnetic polarity reversal N

reversed magnetism reversals Rocks found farther from the ridges have a _____________ magnetic polarity. Parallel stripes of ________________ on either side of these ridges preserve the record of many ____________ of the earth’s magnetic field. reversals

Sea Floor Spreading Video

dark dense C. The _______ _________ (basaltic) igneous rocks of the crust near the ocean ridges are covered with a thin layer of ____________. sediment

This is evidence that the earth’s crust is very ___________ near the ridges. young

The oldest parts of the ocean crust are found far from the ___________ ridges and near the _______________ ocean continents

Observation- as you increase distance from the ridge there is an increase in in the thickness of the layer. Inference: The thicker the layer of sediments on top the ocean floor the older the crust is because more time has passed

Magnetic Poles Shifting Video

Acceptance of Sea Floor Spreading (Plate Tectonics) 1970’s - rapid confirmation of remaining predictions and acceptance of the basic theory by most geologists. 1980’s - Plate Tectonics becomes the dominant paradigm in geology. 1990’s - Development of a detailed plate tectonic history of the last 700 million years. Continental Drift Song Plate Tectonic Whistle