AS17-1828(M)/AS17-1825(M)

Figure 38

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This mosaic of vertical frames covers part of the same area shown in the preceding oblique view (fig. 37), but shows the Montes Apenninus in much more detail. So that the two pictures can be oriented and compared, the same two craters have been identified in each picture by numbers. The bulk of the mountain chain consists of giant blocks of lunar crust that were lifted and tilted outward by the impact that formed the Imbrium basin. These blocks have been covered by an unknown thickness of debris ejected from the basin. The hummocky deposits (H) probably were formed by the base surge a turbulent cloud of fluidized debris that moved outward along the surface from the point of impact. The hummocks resemble huge dunes. Their dimensions indicate a velocity of flow in excess of 100 km/hr and a maximum thickness of the deposits of several kilometers.

The Imbrium event is believed to have occurred 3.95 billion years ago. Later the basin was almost completely filled by successive flows of basaltic mare material. The same material also inundated parts of the outer edge of the Apennine Mountain chain, as in the lower right corner of the picture. -H.M.