Two types of maps commonly used to show the surface areas of the ocean basins and continents are equal-area maps and cylindrical-projection maps (see Figs. 1.6 and 1.7). In Figs. 1.7 and 1.8, a grid is superimposed on the map. At the equator of each map one square represents a surface area of about 1,240,000 square kilometers (or 1.24 X 10⁶ km²).  

 

---

An equal-area map is created by treating the earth like an orange. To get the orange peel to lay flat, it is necessary to make a lot of cuts (Fig. 1.8 A). To make a cylindrical-projection map, think of the earth as a clear globe with black outlines of its features lit from within. To make a flat map, the globe is wrapped in a paper cylinder and the projections of the outlines are traced (Fig. 1.8 B).