The Big Idea of this unit is that the earth is composed of layers that, through heat and pressure, cause movements that result in geological features above and below the earth’s surface. Tectonic plate theory explains how mountains, volcanoes, and trenches are created on land and under the sea. Information about the rock cycle, weathering, and erosion also explains how the earth is continually changing. This unit explores the relationships between these different geological processes and how they affect the landscape and related environments of the earth.