Presentation on theme: "What formation is this? Geologial deposits at Hólar in Hjaltadalur Compressed verion Christian Keller."— Presentation transcript:
What formation is this? Geologial deposits at Hólar in Hjaltadalur Compressed verion Christian Keller
Deserted farm: Hólakot
The upper end of Hjaltadalur demonstrates the U-shaped profile of a glacier-excavated valley
Note the erosion fans along the sides of the valley
The meandering Hjaltadalsá has cut a ”free” profile into a low hill, so we can see inside it
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
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.
Above the notch, there are near-horizontal deposits. A white layer near the top is a tephra layer, possibly Hekla 3000
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.
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