This chapter is about processes that are primarily driven by gravity. There is some overlap with previous chapters, particularly the chapter on soil flow and creep (Chapter 9) where slow moving processes without soil or saprolite failure were discussed. In this chapter the distinguishing features of the processes are (1) the process begins only after failure of the strength of the material, the trigger mechanism, and (2) the subsequent transport of the material is fast. These two features are linked because if there is a strength failure then immediately after the failure there is significant force imbalance (typically the force constraining the movement has disappeared as a result of the failure) and the soil/rock mass is rapidly accelerated by this force imbalance. While these two processes are conceptually linked it is convenient below to treat them separately. In contrast the processes discussed in Chapter 9 do not involve a failure mechanism, and consequently the dramatic and sudden force imbalance does not exist.