Chapter 4: Plate Tectonics and Marine Geology
Modified from "Physical Geology" by Steven Earle*
Learning Objectives
After reading this chapter you should be able to:
- explain Wegener’s original evidence for “continental drift”
- explain how paleomagnetic evidence supports the theory of plate movement
- explain mantle convection – the process that moves plates around
- identify the different ways that tectonic plates can interact with each other, and the various geological features that result from these interactions.
- describe the differences between passive and active continental margins
- define geological features such as seamounts, guyots, and hot spots
- explain why some island systems such as Hawaii are formed in chains
- explain how coral reefs evolve from fringing reefs to atolls
- explain the processes behind the formation of hydrothermal vents
In the previous chapter we learned about the crust as the solid outer layer of Earth. But the crust is not a single, solid piece; instead, it is broken up into about a dozen major plates that constantly move past each other, reshaping the surface of the Earth through the process of plate tectonics. Plate tectonics is a model that explains the origins of continents and oceans, folded rocks and mountain ranges, earthquakes and volcanoes, and continental drift. Plate tectonics was first proposed just over 100 years ago, but did not become an accepted part of geology until about 50 years ago. It took 50 years for this theory to become accepted for a few reasons. First, it was a true revolution in thinking about Earth, which was difficult for many established geologists. Second, there was a political gulf between the main proponent of the theory Alfred Wegener (from Germany) and the geological establishment of the day, which was mostly centered in Britain and the United States. Third, the evidence and understanding of Earth that would have supported plate tectonic theory simply didn’t exist until the middle of the 20th century. This chapter will examine the evidence for plate tectonics and the mechanism by which it works. Following this, we will discuss the consequences of plate motion and the various geological features that can be explained through this revolutionary idea.
*”Physical Geology” by Steven Earle used under a CC-BY 4.0 international license. Download this book for free at http://open.bccampus.ca
the uppermost layer of the Earth, ranging in thickness from about 5 km (in the oceans) to over 50 km (on the continents) (3.2)
a region of the lithosphere that is considered to be moving across the surface of the Earth as a single unit (4.1)
the concept that the Earth’s crust and upper mantle (lithosphere) is divided into a number of plates that move independently on the surface and interact with each other at their boundaries (4.1)
the idea that the continents have moved over the surface of the Earth over geological time (4.1)
