Rauðhellrar (red caves) is the name of the Morsárdalur west side. On a sunny day the red color of Rauðhellrar is quite noticable. For the geologist Rauðhellrar offer a spectacular cross section of interesting strata.
The hiking trail crosses the edges of these screes. The Rauðhellrar are mostly made of “moberg” or brownish massive material that formed through explosive eruptions beneath ice during a few glacial periods. Along the lower part one can see a dipping surface. This is an unconformity or an erosion surface after one of the many glacials found in the area. This is the fourth erosion surface in Morsárdalur or RF4. Rock units above it were dated at 2.81 million years or almost to the greatest impact of the ice age. An unconformity means that the units above and below the line (unconformity) have a different dip. This indicates considerable age difference between units on either side of the “line”. Studies of this line show that glacial erosion was intensive when it formed. Further in the valley, as the Kjós begins to open up, lavas are visible in between layers of moberg. To better realize this one can visualize the stratigraphic sequence on the bedrock map of Rauðhellrar below and look closer at cross section KB.
The line KB is drawn through Rauðhellrar, from base to top in the gully shown on the photo below.
Line KB denotes that a stratigraphic cross section has been studied as can be seen on the photo below.
In the cross section lavas and “moberg” (or palagonite) alternate. A few lavas in a sequence are termed “formation” or in this case “lava formation”. The moberg present inbetween lavas is also defined as a formation or “moberg formation”. Thus, in cross section KB there are a total of 4 lava formations and 5 moberg or palagonite formations. These formtions, with lavas and moberg respectively, bear witness to 4 warm periods or inter-glacials and 5 cold periods or glacials. The area was presumably ice free during the inter-glacials but was covered with glaciers during the glacials. In addition the surface below each lava formation is defined as an erosion surface, shown with a red line on the map. Explanations for the stratigraphic cross section is on the figure below. Cross section KB is easily accessible and rates among the easier in Skaftafell. Near the top of section KB we come across strata that originate from the central volcano in Kjós. It is noteworthy to see strata here that suggest very rapid changes when explosive volcanism start in the Kjós central volcano. White acidic rhyolite layer dominated the sequence at this time, some 2 million years ago.