Overview

In this lab students use data about plate motions and topography to answer questions about seafloor spreading rates and plate boundary types.

Plate tectonics is the grand unifying theory in geology. It gets that title because many topics in geology can be explained  in some way by the movement of pieces of Earth’s outer rigid layer. The pieces are called tectonic plates. There are 15 large plates (Figure 2.1), and numerous smaller ones.

Tectonic plates are composed of Earth’s crust and the uppermost, rigid portion of the mantle. Together those layers make up the lithosphere (Figure 2.2). Tectonic plates can move because the layer beneath the lithosphere—the asthenosphere—is weak. You can think of the asthenosphere as a slippery layer that allows the plates to slide and spin (slowly, of course).

Earth’s tectonic plates all move at different rates, and in different directions. If that sounds like Earth’s surface is engaged in a perpetual chaotic traffic snarl, you have the right idea. In fact, plate tectonic theory is useful because it turns out that we can explain a lot based on what happens as the plates interact with each other along their edges. Those interactions can explain many characteristics of Earth’s surface, including where mountains, valleys, plains, and oceans exist, and where volcanoes and earthquakes happen.

In this lab you will learn about the different types of interactions that happen between plates, how fast plates move, and how we can use earthquakes, volcanoes, and other data to map out the edges of plates.

Learning Outcomes

After completing this lab students should be able to:

• Describe the different types of plate boundaries and identify them in diagrams.
• Describe the landforms characteristic of the different plate boundaries.
• Use topographic data and data about the age of the ocean floor to pick out plate boundaries.
• Compare and contrast the characteristic earthquake and volcanic activity along different plate boundaries.

Key Terms

• Plate tectonics
• Tectonic plate
• Lithosphere (continental, oceanic)
• Asthenosphere
• Divergent plate boundary (ocean-ocean and ocean-continent)
• Convergent plate boundary (ocean-ocean, ocean-continent, continent-continent)
• Transform plate boundary
• Mid-ocean ridge
• Trench
• Volcanic arc (island, continental)
• Subduction zone
• Non-volcanic mountain belt

Attributions

Adapted from The Story of Earth: An Observational Guide, Chapter 1. Plate Tectonics by Daniel Hauptvogel and Jinny Sisson. CC BY-NC-SA 4.0