Continental Drift Hypothesis
• • • • Fit of the continents Fossil evidence Ancient mountain ranges Past climate evidence
Swamps formed in tropical regions
Glaciers formed at the south pole
• The continental drift hypothesis proposes that the continents were assembled to form the super continent Pangaea. • Moved through time
The Appalachian Mountains
Swamps
300 million years ago
Evidence of Ancient Glaciers
•Glaciers carve the rock as they move.
•Scientists can determine the direction of movement (notice the direction of movement noted in South America) •As South ica sits today, the pattern would not make sense. (glaciers do not move from sea level to higher elevations)
the mantle or asthenosphere
What is the composition of lava associated with continental crust?
High percentages Si, O Low percentages Fe, Mg
The Theory of Plate Tectonics
Lack of mechanism to explain continental movement.
• Evidence implied that the continents were at one time assembled • Wegener’s idea was not accepted by the scientific community because he could not explain how the continents moved • With advances in technology, new information was gathered in association with WWII
More Data
Theory
Continental drift hypothesis: evidence?
• Proposed in 1911 • All evidence found on the continents • Mechanism for moving the continents was not known
• Based on two hypotheses
– Continental Drift – Seafloor spreading
Explain the development of the theory of plate tectonics in terms of the scientific method.
The same sequence of rocks is found in North America, Great Brittan, and Norway. The pattern does not make sense with the continents in their current configuration.
What is the composition of lava formed on oceanic crust?
High percentages Fe, Mg Low percentages Si, O
DESCRIBE A CONVERGENT PLATE BOUNDARY
What is the source of the lava that forms oceanic crust?
New Zealand Earthquake
• M 6.3 earthquake • Shallow epicenter: 23 miles • Close to Christchurch, city of 370,000 • After shock to the September 4th M 7.1
Fossil Evidence
• Similar terrestrial species were found on many continents now separated by oceans. • Information collected by paleontologists
Ancient Mountain Ranges
3:20
Fit of Continents
• Antonio Snider-Pelligrini (1858), a geographer cut out a map of Africa and South America suggesting they were connected at one time • Other physical evidence based on observation was used by Wegener
Continental Drift Hypothesis
• Alfred Wegener proposed the hypothesis of continental drift in 1911 • He gathered information from many different sources and used it as evidence for his hypothesis
The Scientific Method
Observation of data or information
One or more ideas, statements or questions; Single or multiple hypotheses
Collection of data Not accepted Hypothesis