Every geographic area has its own problems. Florida has its hurricanes, central USA has its tornado alley, and on the west coast, we live in fear of "The Big One". An earthquake so big that it will have catastrophic consequences. Periodically, the media revives details of the superquake, and reminds us that there is small chance of it occurring sometime in the next 50 years.
Imagine placing a few air mattresses in the middle of a swimming pool and letting them sit there for a few days. Do you think they might all stay together? Do you think they might stay in the middle? We would have to consider a wide range of different possibilities based on what factors might cause them to move.
Scientists have noticed a great deal of evidence to suggest that the continents are not just sitting in place on the Earth, and that the continents are in fact drifting very very slowly. In this section, we will learn what Continental Drift is and some of the reasons that scientists believe it is actually taking place.
- Notes. Template available here.
- Textbook p506-517
- Workbook p207-p213
Assignment: What is the Mechanism of Continental Drift?
- Using the file 12.1.text.pdf, you will read and and make notes explaining how Continental Drift may occur. Follow the instructions given:
- Define "Tectonic Plates." What are found along the edges of tectonic plates and help us identify their boundaries?
- Explain what the "MidAtlantic Ridge" is.
- The MidAtlantic Ridge has been suggested as a source of Continental Drift by a method called "Sea Floor Spreading". Explain what sea floor spreading is and draw a diagram to show how it might make the plates on either side of the Ridge move.
- There are 2 strong pieces of evidence for Sea Floor Spreading: the age of rocks found on either side of the ridge, and paleomagnetism. Explain each and draw a diagram to show magnetic striping and the ages of rocks on either side of the ridge.
- "Hot Spots" allow for the creation of volcanoes without being near the border of a tectonic plate. Explain what a hot spot is. The first 1:20 of this video might help: The Hawaii Hot Spot
Things you should know after today:
- what is the theory of continental drift?
- what evidence do we have that continental drift actually occurs
- what is the mid-Atlantic Ridge
- how does continental drift occur
- keywords: tectonic plates, ridges, paleomagnetism, hot spots, magnetic striping