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What formation is this? Geologial deposits at Hólar in Hjaltadalur Compressed verion Christian Keller.

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Presentation on theme: "What formation is this? Geologial deposits at Hólar in Hjaltadalur Compressed verion Christian Keller."— Presentation transcript:

1 What formation is this? Geologial deposits at Hólar in Hjaltadalur Compressed verion Christian Keller

2 Deserted farm: Hólakot

3 The upper end of Hjaltadalur demonstrates the U-shaped profile of a glacier-excavated valley

4 Note the erosion fans along the sides of the valley

5 The meandering Hjaltadalsá has cut a ”free” profile into a low hill, so we can see inside it

6 The upper part of the sediment consists of coarser and finer material sorted in layers. Thie indiacetes that they are deposited by water, running at various speeds: Fast water = larger particles. The layers are oblique. This indicates a violent river where water is moving downhill fast. Suggestion: A glacifluvial deposit The lower part of the sediment consists of fine, sorted material in near-horizontal layers. This indicates a deposition in deeper, calmer water. Suggestion: A glacifluvial deposit either in the sea or in a lake

7 The glacifluvial layers have been cut through by running water creating a V-shaped notch. It suggestss the formation at this point was above water. The notch was later filled with finer material.

8 Above the notch, there are near-horizontal deposits. A white layer near the top is a tephra layer, possibly Hekla 3000

9 On top of the deposits are large stone blocks. Their edges are only slightly rounded (small picture). They must have been left by a glacier overrunning the older deposits.

10 Rocks tell a story: Sharp edges (far left) tell of a recent, local break-off Slightly modified edges (mid left) indicate some erosion Heavily rounded edges (mid right) indicate serious moraine activity Rounded stones (far right) indicates river tumbling


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