Trascrizione
In this room, we will delve into the theory of plate tectonics, which explains the movements of the Earth's crust. Please approach Showcase 5, where you will find charts and visualisations related to the complex structure of the Earth. The outermost part of our planet is called the crust, or lithosphere (lithos means rock). Below it lies the mantle, composed of continuously moving molten magma, and at the centre, the Earth's inner core.
The Earth's crust is broken into plates, called lithospheric plates, which float on the mantle and move according to the movements of the magma. When these movements push two plates apart, hence called divergent plates, magma emerges from the fracture, solidifying to create new crust. When they bring two plates closer to each other, depending on their composition the convergent plates either collide and form mountains, or one of them partially slides beneath the other, in which case they are called strike-slip plates.
If you approach Showcase 6, you will see how the African Plate and the European Plate began to converge a little over 100 million years ago (which would correspond to a year for our person-Earth, Gea). Initially, the two plates were on opposite sides of an ancient ocean, the Neo-Tethys, and during the collision, the crust beneath the ocean, which was more elastic, slid beneath the African Plate. This is called subduction, which results in the accumulation of crust fragments and sediments. However, the two plates continued to approach until their continental parts, which were harder and more resistant, collided, leading to the displacement and overlap of enormous masses of rocks, deforming the entire Alpine region. Consider that in the geologically short period of about fifteen million years (less than two months in Gea's life), the central part of the Alps was uplifted by more than 20 kilometres and laterally shifted along... well, you've already guessed it, along the fault called the Insubric Line!
Now, take a look at the geological maps displayed in Showcase 7, where each colour corresponds to a geological formation. As you can see, the northern part of Valtellina is much more colourful than the more uniform southern part. This is because Valtellina emerged from the collision of the two plates we discussed: a continental part with a longer and more eventful history to the north, with all the colours, and a southern part that was once the ocean floor. By understanding how the rocks that make up the surrounding mountains were formed, that is knowing about the volcanoes, islands, seas, and rivers that composed the landscapes of the past, we can understand the different nature that characterises them. Showcase 8 presents igneous, sedimentary, and metamorphic rocks.
The first, igneous rocks, form through the cooling and solidification of magma and are classified as intrusive or plutonic when they solidify within the Earth's crust; and effusive or volcanic when they erupt on the Earth's surface as volcanic lavas. Sedimentary rocks, on the other hand, form through the accumulation of sediments, such as small fragments of other rocks, shell fragments, mud, and, in recent times, even plastics and microplastics that deposit and solidify into new rocks. Finally, metamorphic rocks form through the chemical and physical transformation of pre-existing rocks. But let's move on to the next room, where you can see examples of each of these rocks found in Valtellina.