Morainic Amphitheatre of Ivrea: Footprints of giant glaciers
The origin of the morainic amphitheatre of Ivrea
Since 5 millions years ago the Adriatic Sea started to retreat from the Alps through the region that the Po Valley occupies today. This land was gradually covered by the sediments originated from the erosion of the Alps.
Later, during Pleistocene (2.5 million years ago) due to the lower average temperature, the Alps begun to accumulate big amounts of ice that started to spread towards the bottom of the valley. Aosta Valley was covered several times by the Balteo Glacier that used to follow the same path of the actual river Dora Baltea, creating the majestic Morainic Amphitheatre of Ivrea. The most ancient sediments created by the first of three ice ages (Mindel glacial period) are still visible on the left side of the Morainic Amphitheatre, in the Biella area. The front moraine and part of the right side were covered by the sediments of a different ice age: the Riss glacial period (700,000 years ago). During this age the best preserved morainic circle was created, the actual Serra d'Ivrea. The third amount of sediments, dated back to the Wurm glacial period (130,000 to 10,000 years ago), is the most recent and is placed between the previous two including some morainic lines of less importance and height.
This mass of ice pushed with incredibile power towards the bottom of the valley a huge quantity of sand and stones of different sizes.
The size of the glacier was mastodontic: 120km length and 800m height, a surface of more than 500km², diameter 30km and circumference 110km. This is still today one of the biggest and best preserved morainic amphitheatres of the world.
In particular, the left lateral moraine of the ancient glacier, called Serra di Ivrea, is the largest formation of its kind existing in Europe and heads with an almost straight path towards the south-east for almost 20 km, then tearing into the hills surrounding the lake of Viverone.
In its downstream run the Balteo glacier smoothed and rounded the sides of the mountains that were on its path carrying the corrosion materials, which mixed with the Pliocene deluge formations below, formed an incredible mixture of mud, sand, pebbles and boulders huge, which transported from the glacial mass was deposited on the front and sides of the glacier forming the majestic Morainic Amphitheater of Ivrea.
In this way very particular and very varied soils were formed in the composition. You can find: micaschists, orthogneiss of Monte Rosa, white quartzites, black gabbro, purple volcanic rocks, green serpentinites, yellow calcschists, crystalline schists, granites of Mont Blanc, fossiliferous sands, granulites, etc. They come from the decay of the rocks of the majestic massifs of Monte Rosa, Mont Blanc, Cervino and Gran Paradiso and are therefore predominantly sandy, abundantly mixed with pebbles of all sizes. They are very poor in organic matter, therefore in nitrogen, a very important feature for high quality productions due to the low yields they determine in the vineyards. A good quantity of potassium is generally present, a very useful element because it favours the accumulation of sugar in the bunch during the ripening period and of phosphatic substances that contribute most to the fineness of the wines. The lands of the Morainic Amphitheater of Ivrea are very acidic and are normally composed of 70-85% sand, 10-20% of silt and 5-10% of clay that guarantee excellent drainage to the vineyards.