Objectives of this chapter

The Earth can be compared to a big thermal engine: its internal heat provides the energy that drives all geodynamic processes and its long term evolution is governed by cooling. The total energy of the Earth depends on its internal structure and composition. How energy is transported in the Earth depends on its physical properties, which are controlled by the thermal structure. Here, we review some basic geophysical information about the present state of the Earth's interior and show how it is related to the thermal regime and the energy budget of the Earth. This chapter is not intended as a comprehensive description of the Earth and its main units and is focused on aspects that are most relevant to heat generation and transport.

Introduction

This chapter is focused on the silicate Earth which is made of a thin crust over a thick mantle, lying above a central metallic core. For the sake of brevity, we do not explain plate tectonics and assume familiarity with some of its basic premises and terminology. Mid-ocean ridges are zones of shallow sea floor where volcanic eruptions and earthquakes occur frequently. The sea floor is formed out of the mantle there, moves horizontally, and eventually returns into the mantle through deep trenches in a process called subduction.