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Torghatten Brønnøysund by Snorre

A cache by Snorre Send Message to Owner Message this owner
Hidden : 07/12/2007
Difficulty:
3 out of 5
Terrain:
3.5 out of 5

Size: Size:   not chosen (not chosen)

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Geocache Description:


Torghatten is a mountain near Brønnøysund at the norwegian coast. From the sea it is a significant landmark because there is i big whole in it. But how could such a big whole be formed?

The coordinates are from the parking place. From there a path goes up to the Torghatten

Up to now the following explanation was usual. Because of the big ice shield of the ice ages the landmasses were about 100 m lower than they are today. On this level the surf could erode the whole into the mountain. After the ice shield melted the weight was gone and the landmasses could rise. So the whole is on the level from today. But meantime the doctrine changed. 20.000 years ago the ice shield reached the continental shelf. With the following warm period the ice retracted and 12.000 years ago there was no ice at all on and around the Torghatten.

Looking to the Atlantic
Scale: 1.70 m high person in the whole

Sea level was about 100 m above the level from today. The exfoliation of the granite shows vertical structures and this brings the physical and chemical weathering especially in the ceiling forward. Sidewards the weathering is not so intense. And these are the dimensions of the whole: length 116 m, height 41 m and width 18m. The ceiling and the sides consist of granite. The biggest blocks which result from weathering you can find at eastern an the western end of the whole. 60 m from the western exit there is knoll in the middle of the whole. This knoll is about 115 m above the sea level from today. Probably the sea could not erode the next 100 m the eastern exit.

The "temperature" of a glacier is very important for shaping a surface. You have to distinguish between warm and cold glaciers. At the bottom of a warm glacier the pressure is so high that the ice melts and the glacier flows plastic. Pieces of rock are carried along at the bottom and these pieces cause scratches on the rocks. If you have a warm glacier you can also find very strong melt water streams which can generate kettle basins. "Cold" glaciers have no melt water and therefore they are not so good in eroding.

On the way up to the whole
The whole itself

The ice shield on and around the Torghatten was a "warm" glacier. So you can expect glacier scratches and kettle basins. On the eastern side of the Torghatten you can find such glacier scratches on the rocks (40 and 100 m above sea level). You can also find these marks at the sides of the whole and on the knoll. Furthermore there two kettle basins with a diameter of 2-3 m near the whole. The scratches and the kettle basins indicate that glacial processes are responsible for the whole in the Torghatten. The influense of the Atlantic in the west with his waves to little.

But now to the tasks which must be solved for the approval of the log.

1) Take a picture of you standing in the hole of the Torghatten with your GPS. It is evidence that you have been there an did not solve the questions from your living-room.

2) Based on the directions of scratch marks give me the directions, the glaciers was moving (if you want, you can lay your compass on a stone with the scratch marks and take a picture).

3) Explain the process of physical weathering.

4) Name one example of a warm glacier and one of a cold glacier. 5) Thesis: a 2.000 m thick ice shield is on the surface of the earth. The weight is so great that earth's crust begins to sink. After the ice age the glacier melts and the weight is gone. With a delay earth's crust begins to rise. Even now the land masses of North America and Scandinavia are still rising. What is the technial term of these phenomena?

So please first send a mail to torghatten_cache@yahoo.no and after that you get the approval for the caches. Every logs not approved will be deleted immediately.

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