Author: Steingrimur Thorbjarnarson

The Golden Waterfall is mainly divided into two steps, the upper one roughly aligned EW and the lower one NS. To be more accurate, the upper step is combined of two smaller steps, namely the upper most division line accurately aligned EW, and the lower rocks with the direction N77.8°E. The next step which is aligned N10.4°E is in line with the upper most part of the gorge extending down from the waterfall.

Both N77.8°E and N10.4°E are derived from the main tectonic direction of N41.4°E of the convection rolls and the West Volcanic Zone with its edge only about 10 km to the west, whereas N77.8°E is 1/4 of the angle from direct north-south to N41.4°E, and  N10.4°E is 1/4 of the angle from east-west to N41.4°E.

This Google map shows the waterfall’s context with EW axis and the volcanic zone direction:

To see it closer:

The calculated values of tectonic directions show the details of the three main alignments of the waterfall.

The Tjörnes fracture zone is monitored on a day to day basis by the Meteorological Office of Iceland. Usually the epicenters show a pattern along the fracture zone, but these days it is different. The alignment is from NW to SE and even more northerly direction is found. This shows that the underlying convection rolls are playing a dominating role creating these earthquakes. On the table showing the strength and depth of the earthquakes it is apparent many of the earthquakes are originated around 10 km below the surface. It is close to the ductile part of the tectonic plate, where the effects of convection cells can be manifested. Therefore the pattern of the Tjörnes faults, more connected to the horizontal forces on the brittle part of the plate does not appear here in a clear way. The pattern of covection cells has been added to the information provided by the Meteorological Office of Iceland, and the main line between convection rolls darkened:

The resemblance is sometimes even clearer than this. Just follow the events on vedur.is.

The hotspring area of Geysir is found within the realms of an old volcanic system. It has existed for thousands of years (http://www.geysircenter.is/?c=webpage&id=102&lid=98&option=links) but Geysir as we know it for the last few centuries is first mentioned in 1294 when it was reactivated by a big earthquake.

According to the analysis of convection rolls, Geysir is located where it is due to the tectonic effects of the polygon surrounding the Southern Lowlands of Iceland. The outer boundary of the polygon of the NE-side, close to the north corner, is under the hot springs. Here you can see the outlines of the polygon marked with red lines:

Besides that, the horizontal pressure within the polygon has created a secondary tectonic alignment, and the relevant fractures cross the area. Here these fractures are marked with red:

The Google Earth map shows the fractures clearly. The polygon has the alignment of N41°E and the derived tectonic alignment has the direction N54°E. It is 1/4th of the angle between convection roll alignment and EW axis, formed  with this regularity due to stability conditions within the ductile part of the tectonic plate.

Besides this, the EW tectonic alignment is also apparent in the slopes of the mountain Bjarnarfell west of the Geysir area.

All this ensures a steady flow of underground water through the Geysir area at the depth necessary to bring heat to the surface.

The two geysers, Geysir and Strokkur are aligned along a tectonic line which can also be calculated (N30.9E) which is 1/4th of the angle between convection roll alignment and NS axis. It suggests that the two geysers are connected with an underground fracture.

The Geysir Hotspring Area

These rules of tectonic line arrangement are found all over the world, and become quite explicit at hot spring areas like Geysir.

The lowest and highest points of Iceland are found side by side in the SE. The area is far from the rift zone, still the convection cells below at 120 km depth are divergent, creating tension to the east and west. The effect of this tension should be noticed at the surface, explaining the unusual lowering of the bedrock which is found just east of Öræfajökull forming the Glacier Lagoon.

A section of the Glacier Lagoon and the glacier tongue Breiðamerkurjökull looks like this:

This shows us that in the future the Glacier Lagoon will probably become about four times longer than it is today. The expansion of it should also slow down soon as can be reckoned from the drawing.

The Glacier Lagoon is in the range of influence of the 64th parallel, just as the edge of Skeiðarárjökull and the top of Öræfajökull. The forces of the convection cells at this parallel make us surprised, and as can be seen from the comparison on Google Earth map, the coastline follows the direction of convection rolls underneath, as well as the edges of the glacier.

The guides of the boats on the lagoon often mention the coincidence that the highest and lowest points of Iceland are found side by side, as the lagoon is over 300 meters deep while Öræfajökull is 2110 meters high. But there are reasons for everything!

This can be compared with a former post about the Vatnajökull polygon.

I had a look at the site of Veðurstofa Íslands (Met Office) and saw a good example of earthquakes lined up in a familiar way.

As the tectonic framework is mainly derived from mantle currents, the alignment of earthquakes can sometimes be calculated:

I have inserted the formula for the convection cell alignment and the relevant line for the direction. Sure it fits!