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Seen from Space 2005

Impact Craters in North Europe

 
Siljan Dellen Lappajärvi Jänisjärvi Suavjärvi
Fig.1 Outskirts of Baltic Sea
(*Click boxed areas A-E to enlarge picture.)

Figure 1 shows the coastal countries around the Baltic Sea during September of 2003. The Baltic Sea appears black in center, and extends north to the Gulf of Bothnia , and east to the Gulf of Finland. Sweden, Finland, Estonia, Latvia, Lithuania, Russia (an enclave) and Poland surround the Baltic Sea clockwise from the west.

An area called the Baltic Shield (*) reaches from southern Norway to Sweden, Finland and a part of Russia (Kola Peninsula and Karelia district). It consists of stable block made in the Precambrian period (after the birth of the Earth 4.6 billion years ago to around 600 million years ago). Metamorphic rocks that some believe to be 3.5 billion years old and the world's oldest class were found in the Kola Peninsula. Since the Cambrian (from 580 million years ago to 510 million years ago) it has eroded without taking crustal changes, and has become flat. Then it came to have the geographic features similar to the Canadian Shield with many lakes that have been eroded by wind, rain and glaciers for many years. Many gigantic impact craters also remain in this area, as you can see in this 250 m resolution GLI image. Every crater of A - E became a lake. The following table shows the order and era each crater was created .

  Crater Diameter Created Era Remarks
E. Suavjärvi 16 km ~ 2400 million years ago
(the Precambrian)
the oldest impact Russia crater in the following Database.
D. Jänisjärvi 14 km 700 million years ago (the Precambrian) Russia
A. Siljan 52 km 361 million years ago
(The end of The Devonian)
The largest multi-ring crater in Europe. Sweden
B. Dellen 19 km 89 million years ago (the Cretaceous) made of two lakes.Sweden
C. Lappajärvi 23 km 73 million years ago (the Cretaceous) Finland
Source:Earth Impact Database maintained by the University of New Brunswick in Canada

The Scandinavian Mountains connected to the north-west side of Baltic Shield were formed together with the U.K., Ireland and the Appalachian Mountains on the east coast of North America during the Precambrian an into to the Devonian (about 600 million years ago to 360 million years ago) by the Caledonian Orogeny. The Caledonian Orogeny caused the collision between the North American plate and Eurasian/African plates. However, since the Permian period (300 million years ago to 250 million years ago), both plates began to separate, and the Atlantic Ocean was formed and continues to expand at a rate of about 3 cm a year.

The area of Northern Europe was covered in a thick glacier during the ice age from 2 million years to 10,000 years ago. The glacier began to retreat about 12,000 years ago. The crust floats on the mantle with a larger density and keeps its balance. This status is called “isostacy,” then the crust that lost weight of a glacier began to uplift. Original uplift speed was 9 cm annually, and continues at a rate of 1 cm a year in the Gulf of Bothnia. It takes 15,000 years to 20,000 years to restore balance.



(*) The Shield is a flat, extensive area composed primarily of Precambrian rocks. If viewed as a whole, the center is a bit higher, and the height gradually decreases in a radial direction. It resembles the shape of a shield used by knights in medieval times, hence it was named "Shield." There are the Canadian Shield, the Baltic Shield, etc.

Explanation of the images:
(Fig.1 and Frames A to E)
Satellite: Advanced Earth Observing Satellite - II (Midori - II)
Sensor: Global Imager (GLI)
Date: September 5, 2003
Color composition was made by using GLI 250 m resolution channels, and assigning red to mid-infrared channel 28 (1,640 nm), green to near-infrared channel 23 (825 nm) and blue to visible channel 22 (660 nm). In these images, vegetation is green, clouds are white or light blue, soil or sparse vegetation is brown, and water surfaces and shades of clouds are black. Frames A to E are partly enlarged images of Fig.1.

Related sites:
Shield memorizing impact craters: Labrador Peninsula, Canada
Circular Farms and Impact Craters in the Sahara
Western Australia, the Red Continent, narrates the Earth's history
Greenland: A White Land Storing 250,000 Year Old Ice

Appendices:
Influence of an uplift:
As the place where an uplift is, two are given in Sweden. One is “Höga Kusten” (HighCoast) located on the west shore of the Gulf of Bothnia. There you can see complicated and strange geographical features such as many islands, inlets, lakes, flat hills 350 m high above the sea level generated by glaciating, retreat of glaciers and the appearance of new lands generated by an uplift. In addition, a good example of the trade network of the Vikings during the eighth and ninth centuries, Birka and Hovgården are registered with the World Cultural Heritage and are located on two islands in LakeMälaren to the west of Stockholm. LakeMälaren was connected to the sea in those days, and prospered as a center of international trade during the Vikings eighth century , but it became extinct by the end of tenth century because big ships could not gain access there due to an uplift.
In Finland they also had to move ports in the sea side in Pori located 230 km northwest of Helsinki and in Vaasa 180 km north of Pori.


The Vikings and their activity coverage:
It was comparatively warm during the time of the Vikings (800-1050). The Vikings left Denmark, Sweden and Norway, and sailed to the European coasts by small ships and carried out active trade. The Danish Vikings arrived at the Mediterranean Sea, the Norwegian Vikings discovered Iceland in 860 and settled there. Some Vikings reached Greenland and North America. The Swedish Vikings reclaimed the following two trade routes by the end of ninth century .

Route 1. Go down the Dnieper from near the Baltic Sea, enter the Black Sea, and continue to Constantinople (Istanbul), the capital of Byzantine Empire.

Route 2. Go down the Volga from near the Baltic Sea, enter the Caspian Sea, and continue to Baghdad, the capital of an Arab kingdom via Baku.

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