1 February 2017

An oddball at Eshaness

Posted by Callan Bentley

Eshaness is in western Shetland, on the Northmavine Peninsula.

It’s a land of Devonian-aged mafic volcanic rocks, a cross-section through a stratovolcano the erupted hundreds of millions of years ago. The powerful forces of coastal erosion have chewed into these rocks, carving Shetland’s edge into a series of cliffs and sea stacks.

The rocks on display are mainly of two types: basalt and agglomerate (lahar deposits or pyroclastic ejecta making a rock sometimes dubbed volcanic breccia). One cliff, south of the lighthouse, shows basalt overlying volcanic breccia:

Zooming in on the top and bottom units:

Outcrops of the breccia nearer to the lighthouse:

And then there was this:

Perched atop the cliff top was an erratic: a boulder of granitic intrusion breccia, filled with angular fragments of older rocks of several flavors. This oddball was likely dropped here when Shetland was last glaciated. There’s nothing like it anywhere nearby.

The other side looks like this:

My son loved it! It seemed friendlier in its polished smooth texture than the craggy, poky agglomerate all around:

Here are three GigaPans of the site, if you’re interested in exploring some of the details. If you don’t have Flash enabled, click through to zoom in and explore them.

Link 0.58 Gpx GigaPan by Callan Bentley

Link 0.48 Gpx GigaPan by Callan Bentley

Link 0.63 Gpx GigaPan by Callan Bentley