Objectives of this chapter

Because of their simple structure, the oceanic plates offer an ideal situation for the application of simple thermal models to geodynamics. In this chapter, we present the cooling model of the sea floor. We shall analyze how the model depends on boundary conditions and discuss how well the model's predictions fit the data. We shall also show how the discrepancies between the model's predictions and the data lead to the inference of hydrothermal circulation in the young oceanic crust, and small-scale convection in the mantle beneath old ocean basins. We shall also use the cooling model to analyze the effect of mantle hot spots on the oceanic plates. Finally, we shall show how the cooling model for the oceanic lithosphere explains many other geophysical observations.

Continental and oceanic heat flow

Introduction

With the sea-floor spreading hypothesis and the advent of plate tectonics, it became clear that oceanic and continental heat flow are fundamentally different. While crustal radiogenic heat production is the largest component of the continental heat flux, oceanic heat flux is due to the transport of heat to the surface of the Earth by mantle convection (Turcotte and Oxburgh, 1967; McKenzie, 1967; Sclater and Francheteau, 1970). The oceanic lithosphere is in a transient thermal state in contrast with continents which are mostly in, or close to, thermal steady-state. Oceanic heat flux is described by a decreasing function of age which parallels that of elevation (or bathymetry).