Money makes a variety of economic transactions possi-ble.
in the following three situations, determine whether money is involved in the transaction. in prison camps during world war ii, and in some prisons today, cigarettes circulate among prisoners. for example, a cell phone might cost 600 cigarettes, whereas a magazine might cost only two cigarettes.
1. discuss whether cigarettes are fulfilling all three func-tions of money in this case.
2. over the last 50 years, credit cards have become an increasingly popular way for people to purchase goods and services. are credit cards money?
3. almost every day, many people sign their names to little pieces of paper called checks, which are then accepted in exchange for goods and services. do these checks constitute money?

51% were unhappy, i think .   ; )

the earth’s crust is broken into separate pieces called tectonic plates (fig. 7.14). recall that the crust is the solid, rocky, outer shell of the planet. it is composed of two distinctly different types of material: the less-dense continental crust and the more-dense oceanic crust. both types of crust rest atop solid, upper mantle material. the upper mantle, in turn, floats on a denser layer of lower mantle that is much like thick molten tar.

each tectonic plate is free-floating and can move independently. earthquakes and volcanoes are the direct result of the movement of tectonic plates at fault lines. the term fault is used to describe the boundary between tectonic plates. most of the earthquakes and volcanoes around the pacific ocean basin—a pattern known as the “ring of fire”—are due to the movement of tectonic plates in this region. other observable results of short-term plate movement include the gradual widening of the great rift lakes in eastern africa and the rising of the himalayan mountain range. the motion of plates can be described in four general patterns:

collision: when two continental plates are shoved together

subduction: when one plate plunges beneath another (fig. 7.15)

spreading: when two plates are pushed apart (fig. 7.15)

transform faulting: when two plates slide past each other (fig. 7.15)