|
13 km |
Individual Time Trial |
Prehistoric continent Baltica |
Prehistoric continent Baltica hides below the Danish subsurface, that contains as much as 12 kilometers of sedimentary rocks, formed in the last 450 million years. Baltica is now part of the Eurasian continent, and stretches from the Atlantic coast of Norway to the Ural Mountains, and from the Arctic Ocean to the Black Sea.
What is a prehistoric continent?
What is a prehistoric continent? They are packages of 30 km thick crust that mostly consists of magmatic rocks that formed above subduction zones. Like below that volcano in Tonga that exploded last winter. These types of rocks are more buoyant than the underlying mantle rocks. When the plate of which they form part arrives in a subduction zone, these rocks are offscraped to form mountain belts, or they even stop subduction. So continents can move along the Earth’s surface together with the plates of which they are part, but they will not disappear. They break off one continent and merge with the next in an endless plate tectonic dance. Baltica too.
Avalonia
About 500 million years ago, Baltica was on the southern hemisphere together with the supercontinent Gondwanaland (which included South America, Africa, India, Australia, and Antarctica), around the South Pole. Baltica moved northward, together with another continent, Avalonia (consisting of parts or Ireland, Wales, and England, Belgium, the Netherlands, and northern Germany). About 450-400 million years ago, Baltica and Avalonia collided with Laurentia (Greenland and North America). Baltica and Avalonia also collided with east other, and the fault along which this happened is located around the Danish-German border. But hidden below an enormous pole of sedimentary rocks that were brought in from Scandinavia and Germany.
Armorica
And France? Most of France is part of yet another continent: Armorica. Armorica collided with Avalonia around 300 million years ago. And the last part of Europe, Adria, arrived in the last 50 million years ago, and the faults along which that happened now form the Alps. So Denmark-France is a day’s drive today, but during Baltica’s heydays, they were separated by a hemisphere and an ocean!
I am a geologist and I study plate tectonics and the driving mechanisms in the Earth’s mantle, mountain building processes, and the geography of the geological past. I enjoy geological fieldworks all over the world, and translating the results to science and a broad public.
Douwe van Hinsbergen