Problem
The current theory of the structure of the Earth, called plate tectonics, tells us that the continents are in constant motion. Assume that the North American continent can be represented by a slab of rock 5350 km on a side and 37 km deep and that the rock has an average mass density of 2600 kg/m^3 The continent is moving at the rate of about 4 cm/year. What is the mass of the continent?