Lesson at a glance: Students will learn the three layers of the Earth, observations that support continental drift and sea-floor spreading, and the basic concepts of plate tectonics.

Key Concepts: The Earth has three layers: the core, the mantle, and the crust. Rigid plates, called the lithosphere, are made of the crust and the uppermost mantle. The plates move on the softer, convecting mantle called the asthenosphere. Plat e margins are identified by the distribution of earthquakes and volcanoes. There are 7 major plates and 20 smaller plates. Plates move towards, away from, or slide past each other.

Lesson Outcomes: The students will:

  1. recognize the major layers of the Earth.
  2. demonstrate that earthquakes and volcanoes help define plate boundaries.
  3. describe the ways that plates move, relative to each other.
  4. examine the steps in proving a major theory.

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