5Alfred WegenerWegener proposed the Theory of Continental Drift which suggests that the continents change position slowly by a few cm a year.He could not explain how.
6Four forms of evidence to support his theory... 1.Shape of the continent- Wegener suggested that all the continents were joined together as a super continent called Pangea and that the continents acted like possible pieces to a puzzle. (ex. South America and Africa)
72nd piece of evidence for Continental Drift Theory 2. FossilsSimilar fossils found on one continent have been found on others. Ex. NL and WalesRefer to page 361
83rd piece of evidence for Continental Drift Theory 3.Rocks and Rock LayersGeologists found rocks that were similar on both sides of the Atlantic Ocean. The ages of these rocks are also the same.
94th piece of evidence for Continental Drift Theory 4. Climate ChangeLocation of coal beds. These should be found in tropical, swampy area BUT have been found in cold and moderate climates.
10Accepted or Rejected?Because he was unable to explain HOW the continents move, his theory was rejected by the scientific community.
11Plate TectonicsIn the early 1900’s, scientists used some new technology to further their understanding of the continental drift theory proposed by Wegener.
12New technological advances include the following... 1. Sonar: provides a more detailed picture of the sea floor. (pg. 364) 2. Magnetometers: provide evidence for sea floor spreading. (pg. 365) 3. Deep sea drilling: provides evidence for the internal structure of the crust. (pg. 366)
13Evidence Collected...Discoveries on the sea floor showed that magma produces new crust which pushes the plates of the Earth’s crust.The plates meet at boundaries. The plates can be moved in three ways.
141. Divergent boundaries: plates moves away from each other. 3 types of boundaries are…1. Divergent boundaries: plates moves away from each other.2. Convergent boundaries: plates movetowards each other3. Transform Boundaries: plates slide past each other.*This idea was developed by J. Tuzo Wilson(Canadian Scientist) during the 1960s.Xcvxcv
15Convergent Boundary Where two plates meet is known as the Convergent
16Divergent Boundary Where two plates separate is known as the Divergent
17Transform Boundary Where two plates slide past one another is known as theTransform boundary
18New Theory...Wilson’s ideas form a new theory in the 1970s.Because it was discovered that the sea floor, as well as, the continents were moving, the plate tectonic theory was born.
19Satellites are helping to measure plate movements. Plate TectonicsThis theory states that Earth’s crust is broken up into pieces, called plates that are always moving on Earth’s mantel.Satellites are helping to measure plate movements.