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Seen from Space 2004

Shield memorizing impact craters: Labrador Peninsula, Canada

 
Charlevoix Clearwater West & East Manicouagan
Fig. 1 Northeast Canada
(*Click boxed areas A-C to see a larger picture.)

Figure 1 depicts Labrador Peninsula in Northeast Canada in early spring of last year. The nothern area of around 50 degrees north was still covered with snow and ice . This image covers Hudson Bay in the upper left, a part of the Great Lakes in the lower left, the Gulf of Saint Laurence, Nova Scotia Peninsula and Prince Edward Island (made famous in the novel and the movie "Anne of Green Gables") in the lower right, and Newfoundland Island and the Atlantic Ocean on the right.

Labrador Penisula is a part of the Canadian Shield (*1), a plateau of granite made 600 million years ago (around the end of Precambrian Era), and is characterized geographically by many lakes formed by erosion from wind, rain and glaciers over a long time. Many gigantic impact craters also remain in this area (*2), and you can find the following craters in this GLI image. (Larger pictures will appear when you click boxed areas A to C.) Some craters became lakes and some were covered with vegetation, depending on when they were created, its geology, subsequent weathering and erosion, etc. The following table shows the craters in the order of created era.

  Crater Diameter Created Era Remarks
A. Charlevoix 54 km 342 million years ago (the former half of the Carboniferous) Only northwest half can be seen in the image. Southeast half is in the bottom of the Saint Laurence River.
B. Clearwater West & East 36 km & 26 km 290 million years ago (border between the Carboniferous and the Permian) Crater chain
C. Manicouagan 100 km 214 million years ago (border between the Triassic and the Jurassic) The largest crater in North America. A part of crater chain.

The Manicouagan crater (C above) consists a crater chain together with Rochechouart crater (25 km in diameter) in France and Saint Martin crater (40 km in diameter) in Manitoba, Canada (*3). "Crater chain" means a chain of craters made by sequential impacts of the pieces broken up of original one terrestrial body like the impact of Comet Shoemaker-Levy 9 on Jupiter in July 1994. There are some crater chains on the Moon and Ganymede, Jupiter's satellite.

"Tableland" in Gros Morne National Park on the west coast of Newfoundland Island is a 600 m high plateau made of p e ridot that was once a part of the upper mantle exposed on the ground surface after breaking through the crust of the ocean floor when the North American Plate and Eurasian/African Plate collided 450 million years ago (the Ordovician). This is one of the main reasons why Gros Morne National Park has been designated a World Heritage Site by UNESCO (the United Nations Education, Scientific, and Cultural Organization).

At L'Anse aux Meadows (meaning cove at meadows) National Historic Site, located on the northen end of Newfoundland Island and declared a UNESCO World Heritage Site, there are archaeological remains of activities of native people around 6,000 years ago and of a settlement of Viking people around 1,000 years ago, or about 500 years before Columbus reached the West Indian Islands.



(*1) 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 the radial direction. It thus resembles the shape of a shield used by knights in medieval times and is called "Shield." In addition to the Canadian Shield, there is also the Baltic Shield and others.

Related sites
(*2) Earth Impact Database operated by the University of New Brunswick in Canada
(*3)News release of the University of Chicago

Explanation of the images
(Fig. 1 and Frames A to C)
Satellite: Advanced Earth Observing Satellite - II (Midori - II)
Sensor: Global Imager (GLI)
Date: April 7 to 22, 2003
These are color composite images generated from GLI spectral channel 26 (1,240 nm) in the medium infrared band (red), channel 24 (1,050 nm) in the medium infrared band (green), and channel 19 (865 nm) in the near infrared band (blue). In these images, snow and ice are white or light blue, soil or sparse vegetation is brown, and water surfaces are black. The original resolution is 1 km.

It is difficult to acqure cloud-free images of this area, even if observed by GLI with 1,500 km wide observation swath because of the climate of this area. We produced the cloud-free seamless image in Fig. 1 by selecting fair parts pixel by pixel from data acquired during the above-mensioned 16 days and composing them by computer processing. This kind of image is called a cloud-free composite image.

Frames A to C exhibit somewhat different coloring because they were partly expanded and image processed to clarify the craters.

Appendix: Tales told of Newfoundland Island
It seems that English fishermen fished off Newfoundland Island in summer as early as around 1500. On the Island shore, dogs unrivaled for hardiness and stamina helped the fishermen. They were carried to England in the beginning of the 19th century and were bred as retrievers. The "Labrador Retiever" was subsequently recognized by the Kennel Club in England in 1903, and they have become familiar as pets, police dogs and seeing-eye dogs.

The Titanic tragedy occured about 650 km southeast off Newfoundland Island from midnight of April 12, 1912 to just before daybreak of the next day (45th year in Meiji Era in Japan); that is 92 years ago. Over 1,500 persons died due to the sinkng after collision with an iceberg. Halifax, Nova Scotia, was the base for rescue activities at that time. Today, you can find a cemetery for the victims, and some articles left by the Titanic are displayed at the Atlantic Maritime Musium there.

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