## 4 Results
### Pre-Landslide Topography and Geology Reconstruction
Thus, the contour lines of the slopes of both sides of the landslide have been extrapolated, both on the slopes above the lateral moraines not affected by glacial erosion with a slope of about 14\({}^{\circ}\), and on the slopes below the moraines, with a slope of about 40\({}^{\circ}\). The limit for the extrapolation of both slopes is imposed by the deduction of the situation of the maximum extent of glacier ice according to the location of the lateral moraines. It has also been taken into account that the axis of the bottom of the valley before the landslide was located about 250 m to the west of the current one, since the mass movement invaded it and displaced the river to the east. This displacement can be very well measured by joining the rectilinear north-south channel of the Urbion River upstream and downstream of the landslide (Figure 9(0)). The bottom of the valley was also about 20 or 25 m above the current one: this can be observed very well in the unevenness of the river embedding in the mass of the slide and in the associated alluvial fan (Figures 2 and 3B). All this has been taken into account to reconstruct the topography of the valley excavated by the glacier that is presented in the geological map of Figure 4B. To reconstruct the geology of the substrate in the valley, the contour map method has been used, drawing geological contacts 22-23 and 22-21 in the pre-glacial topography, for which the current outcrops and dips have been used. This is what is represented in Figure 4B, that is, the geology of the substrate under the surface formations of the moraines, the mass of the landslide and the alluvial fan. On the topography of Figure 4B, the thickness of the lateral moraines has been added, supposedly covering the entire valley. The end result is a topographic map of the valley floor before the slide, under the ice of the tongue, which is not shown here. In Figure 4C the exterior topography is represented with the level curves of the glacier surface at its maximum apogee, assuming this gently convex and slightly asymmetric surface as a result of taking into account the altitudes of the moraines, of about 25 m higher elevation on the left than on the right. We have assumed that the bottom of the valley is the situation of the maximum glacier phase, and that this bottom no longer descended when the glacier was receding. If we admit this, it follows from these maps that the maximum thickness of the glacier tongue at its maximum advance was, in this zone of the slide, of no more than 140 m.  
4. Reconstruction of the topography during the retreat of the Pico de Urbion glacier. Although the logical thing was to think that the slope would failure until the complete disappearance of the glacier, canceling the wall-wedge effect of the ice at the foot of the slope, they have tried to simulate the intermediate situations in the retreat of the glacier to exhaust all the possibilities. Thus, in Figure 4D, the topography in the glacial retreat is represented by way of example, considering a thickness of the ice tongue of 40 m and keeping the bottom topography constant. In the latter situation, the glacial front had recoded almost 2 km and was in this sector of the valley. The end of the glacier was residually restricted to the narrow valley bottom, increasing its volume on the rise of the topographic step of contact 21-22. If we look at the profile corresponding to the final situation in Figure 9(2), the difference in slope level has increased with respect to before the glaciation from 300 to 375 m and, with respect to the slope, it remains 14\({}^{\circ}\) above 1675 m, up to 1900 m from the summit. It has increased in the lower part to 40\({}^{\circ}\) from 1675 m to the bottom, located around 1525 m.  
Figure 5 shows two geological sections along the landslide where it can be seen that practically the entire unit (22) has been mobilized, limit of the failure in depth, and which has been exceeded in the foot of the slide. The dip, relatively in favor of the slope, has contributed to the landslide.