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Geological and glacer signs at Åselistraumen.
Sign 1. By the moraine at Åseli
Imagine that the time is turned back 10.000 years. Then you would have stood in front of the ice sheet (shown with the red arrow). In the front of the ice was a ridge of stones, in different sizes, located (as the picture shows). The deposition was a result of the ice digging into the bedrock. Stones was excavated, then carried to the snout of the ice and deposited.
Question: From where you stand- can you see traces of the moraine?
The stripes you see in the bedrock are called striations. These were formed when the ice sheet covered the area about 10.000 years ago. Rocks frozen into the base of the glacier abraded the bedrock like a giant piece of sandpaper. Striations are thus traces of glacier movement, and while they do not indicate the directions of the movement, we must find other landforms, so called cresentic gouges and roche mountenèe, to reveal that to us.
Sign 3 By the cresentic gouges
The crescentic gouges you see here were formed when rubble materials were frozen into the base of the glacier, and pressed forcefully against the bedrock. When the pressure became great enough, the rock cracked into splinters along a crescent arc, and a crescentic gouge was formed. The part of the sickle which grades the most steeply into the rock is directed toward the movement of the ice.
Sign 4. By the roche moutonèe
Here you can see a roche moutonèe. It was formed by glacial freezing and thawing. Here the glacier met a bump in the bedrock, such as a rocky knoll, the pressure on the impacted side caused some of the ice to melt. Melted water fleew on the leeward side of the elevation and penetrated the cracks. The released pressure caused the water to freeze again, which could result in cracking of the rocks (see figure underneath), and a steep leeward side was eventually developed.
Short summery of the traces from the last ice age in the area.
The moraine, striations, cresentic gouges and roche moutonèe are traces from the last ice age. They show that the ice moved northwest towards the fjord (mark with a red arrow on the map). The moraine, by the road, was deposited in front of the ice during a stop in the retreat of the ice sheet between 10,000 and 10,500 years ago. Then the ice disappeared from the area because the climate became warmer.
Sign 5. The bedrock
The bedrock tells of large-scale geological processes that took place about 470-430 million years ago when Norway and Greenland collided. The bedrock was folded and a great mountain range, the Caledonian, was formed (see figure). It was just as long and just a tall, if not taller, than today`s Himalaya.
The Caledonian mountains have since eroded, but the bedrock surface that remains today is a window into what once was. We can, in many places in this area, see the folded mouintains in miniature.
Try to find examples in the bedrock.
Saltstraumen Museum - Knaplund - 8056 Saltstraumen - Nordland Fylke - Telefon 755 87500 - Konto: 0539.66.26812
|Publiseringsløsning levert av Seria AS|