DISCUSSION

 

Impacts of the landslides in the landscape are a crucial process in the geomorphology of the relief (Cendrero and Dramis, 1996) and in the Canary Islands, the landslides and the post – volcanic activity are modifying the slope, hydrological network and also, it has influence in the distribution and diversification of the vegetal communities (Villalba 1996) mainly in Tenerife, El Hierro y La Palma (Canals, 2000).

 

Seafloor studies have revealed the landslide materials in the ocean which are easier to analyse due to good conservation status. However, on the surface of the islands the erosion and volcanic activity have deleted the resulting morphology of the landslides and this makes it difficult to study (Urgeles, 1999).

 

The slope is a good indicator of the landslide limits in the islands. In general can find high slopes in the landslides of Tenerife and El Hierro, but sometimes these bounds are not clear or do not exist such as El Julán in El Hierro or Icod and Los Roques de García in Tenerife where there is an overlapping between both landslides. It limits the definition of the landslide areas and consequently, there is a margin of error in some landslide areas defined. Moreover, slope evinces the volcanic activity in the landslide areas but this tool is useful in the landslides where the erosion has not been very high and volcanic activity has been low.

 

The hydrological network is confirming the role of the cliffs generated by landslides and the important character of the volcanism in the streams as El Teide (Santamarta et al, 2013). It implicates that the streams of Tenerife and El Hierro are exposed to high pressure due to volcanic activity, and it can change the erosion processes after eruptions.

 

The land use analysis has given relevant information about the occupation and distribution in landslide areas. Maps of land use are accessible in GRAFCAN and limits do not exist to get the information. The slope is affecting to the land use distribution, but areas with and without landslides have the same percentages in the occupation and it means that occupation could be modified, but in general the activities have the same total area in the land. For future researchers, land use could be interesting analyse with more different types of occupation and try to find some differences in the vegetal species distribution and agriculture activity. Also, differences between some landslides have been found mainly between El Hierro and Tenerife due to the economic activity in Tenerife is higher than El Hierro and, the influence of the high slopes in the boundaries of the landslide areas which determinate the anthropogenic activity and the vegetation occupation in these areas.

 

Other important point in this research is the uplift in the Canary Islands especially, in Tenerife where the uplift movements are affecting to the coastline of the island (Maurer et al., 2008). According this author, the island experiment an uplift process derived from the weight of the new islands, but erosive processes and in particularly, landslides processes are also affecting the local uplift in the island due to the materials lost in the land surface after the landslides. More researchers about the deposit in the land of Tenerife could give important information about these processes in the islands, and explain the combination between the regional and local uplift cause for the landslides or subsidence due to the new volcanic activity in the area. In fact, Watts and Masson (1995) explain the uplift and subsidence processes in Hawaii due to volcanic activity, and use this to explain these processes in Tenerife where landslides succeed 5 ma ago, uplift and erosion were the main factor 3 ma ago, subsidence processes 1.5 ma ago and the recent landslides in the last 1 ma. However, uplift and subsidence processes cannot be explained without analyse the regional processes because according Hildenbrand et al., (2003) and Meco et al., (2007), subsidence and uplift processes are affecting to the islands. The first author says La Palma has signals of regional movements of uplift, and the second author explain the elevation of the islands cause to the weight of each one. Therefore uplift is affecting to the landslides areas, and is an important factor in the landscape of the island, but landslides are affecting to the uplift as well so, it is a loop process where both elements are important and have a relationship between them.

 

In summary, landscape of Tenerife is being affecting for several geomorphological processes that are influencing in the most of the cases all together. Land use of the island is controlled for volcanic activity, land movements and landslides although, the human societies try to control the natural processes until an extreme event succeed as Arenas Negras volcano in Garachico in 1706. This volcano destroyed the main port of Tenerife (GEVIC, 2014) and the old town. Actually, a new town is in the same area and a new port has been built.