The mountain belt of the Sierra de Gredos consists of an IGNEOUS rock called GRANITE; this rock may be easily identified by its mix of white, black and pink colours. Granite is an INTRUSIVE igneous rock which means that it was formed as a result of magma being “injected” into the earth’s crust as a large “lump” or mass known as a BATHOLITH. This rock mass is now at surface level due to a combination of two factors: • a period when the rocks were uplifted (about 25 million years ago) • subsequent denudation of the overlying sedimentary rocks by weathering and erosion.
When a large rock mass is uplifted in this way, it is called a HORST, and it is usually heavily faulted and jointed.
Many of the landforms seen in the Sierra de Gredos today are the result of glaciation. Which was most recently at its height about 15.000 years ago. At that time there were approximately 40 glaciers in the area, the largest of which was possibly as by as 10 km long and 300m thick. Today we can see a variety of post glacial features at various scales of size: * Macro:
the very shape of the hills, with smooth outlines up to 1500m.
sharp angular peaks known as horns or pyramidal peaks
deep, steep sided, flat bottomed U shaped valleys, known as glacial troughs.
Corries or cirques.
hanging valleys with waterfalls.
Knife-edged ridges or arretes
Striations (scratches) on rock surfaces.
Polished rock surfaces.
Areas of loose material: moraine
Since the end of the last ice age 10.000 years ago, the landscape of the area has continued to develop by a combination of weathering and erosion processes. Granite is a resistant rock that is non porous but it is susceptible to both physical (freeze-thaw action) and chemical weathering (hydrolysis). Orientation (direction of flow) is much influenced by the relief of the Gredos range which is basically E-W. Precipitation patterns are different on each side of the range: Most erosion in the area is caused by the action of fast flowing rivers. Due to the non porous nature of the bed rock there is a high drainage density, and, fed by the uppers snowfields during the dry summer months, rivers continue to flow throughout the year. Landforms associated with river erosion are:
meanders and cut-off meanders
Three factors affect the climate of the area:
The semi-continental nature of the Iberian Peninsula.
The altitude of the area.
The orientation of the range of mountains (E-W).
The first factor results in a climate that is wet and cold during the winter months and dry and hot in the summer. However the altitude and orientation of the Gredos Mountains mean that the area is generally a lot wetter and cooler than the surrounding lowlands.
SETTLEMENT PATTERN OF THE AREA
The capital of the province of Avila is the town of the same name, the walls of which date from about 1090. It has a population of some 50,000 people although this official figure is increased to almost double that during the working week, with people from the surrounding rural areas commuting on a weekly basis. Villages within the National Park are mainly located along the C500 route linking the N501 (national road) in the E with El Barco de Avila in the West.
Navarredonda de Gredos and Hoyos del Espino, approximately half way along the section of road that runs along the range itself, are the settlements that have expanded most due to the influx of visitors to the area, It is the entry point for most walkers, skiers and rock climbers into the range via the” Plataforma”, a parking area on the foot of the main path leading into the mountains. This parking area can be considered a ‘Honey pot’ location. The village has a large Visitor Centre and in the height of the season a shuttle bus service for walkers from the village to the parking area has been planned.
Farming has traditionally been the main form of economic activity throughout rural areas of the region, pastoral farming being by far the most important activity. Transhumance is practiced with cattle spending the winter months November-May in the lowlands areas of Extremadura, and being brought up to the upper pastures in June once the grass in the upper meadows has had time to establish itself.
More recently tourism has become a more important activity in the area, bringing both positive (employment, growth, earnings) and negative (visual pollution, overcrowding and traffic congestion) impacts. Periods of high tourist numbers are during the months of July and August, and national holidays. Weekends are also very important to a large number of the residents of Madrid, who have second or holiday homes in the area.