A spectacular pitchstone ridge on the Isle of Eigg Scotland, rises out of the surrounding small islands landscape.
Sgurr, which means The Notch, has sheer cliffs and is 400 meters (1300 feet) high.
The island mountain Sgurr of Eigg in geology is known as a monadnock in the USA, inselberg in Europe or a koppie in Africa. These are lonely mountains, hills or buttes with different rock to the local area they rise up from.
Pitchstone An Sgurr
An Sgurr was formed as lava poured though a prehistoric riverbed from a volcano on the neighbouring island Rum. Over millions of years, the surrounding land has eroded, leaving the harder pitchstone ridge behind.
An Sgurr (The Notch) | Isle of Eigg
Pitchstone volcano glass rock is famous for its high water content that makes it appearance much duller than obsidian.
For a valley mould of Sgùrr size on a small island how would a stream have enough volume of water while lava pouring out? Eigg is only 5 miles by 3 miles.
How would a stream keep flowing into and through the lava to create pitchstone up to 200 meters thick?
The pitchstone mountain also has similar hexagonal columns to the Giants Causeway in Northern Ireland.