Travel Reference
In-Depth Information
by the creation of the new island of Surtsey in the 1960s. Looking like mini-volcanoes
but actually nothing of the sort, aptly named
pseudocraters
- like those at Mývatn and
Kirkjubæjarklaustur - form when lava flows over damp ground, vapourising the water
beneath, which explodes through the soft rock as a giant blister.
Most
rocks
in Iceland were created in volcanic eruptions, and two common forms are
easily identifiable.
Basalt
forms fluid lava solidifying into dark rock, weathered expanses
of which cover the Reykjanes Peninsula and elsewhere. Where basaltic lavas cool
rapidly - by flowing into a river or the sea, for instance - they form characteristic
hexagonal pillars
, with excellent examples at Svartifoss in Skaftafell National Park and
Hjálparfoss at Þórsárdalur. In contrast,
rhyolite
forms a very thick lava, which often
builds up into dome-like volcanoes such as Mælifell on the Snæfellsnes Peninsula.
Cooled, it normally produces distinctively crumbly, grey, yellow and pink rocks,
typified by the peaks of the central Landmannalaugar region, though in some cases
rhyolite solidifies into black, glass-like
obsidian
(best seen at Hrafntinnusker, on the
Laugavegur hiking trail). Types of tephra to look for include black or red, gravel-like
scoria
; solidified lava foam or
pumice
, which is light enough to float on water; and
bombs
, spherical or elongated twists of rock formed when semi-congealed lava is
thrown high into the air and hardens as it spins - they can be as big as a football but
are usually fist-sized.
Aside from their cones and lavafields, volcanoes affect the landscape in other ways.
Historically, dense clouds of tephra have destroyed farms and farmland on a number
of occasions - such as the twelfth-century eruption of Hekla that buried Stöng in
Þórsárdalur, or the 1875 explosion of Viti, at Askja. Volcanic activity under ice caps
can also cause catastrophic flash floods known as
jökulhlaups
, the most recent being at
Grímsvotn in 1996. On the other hand, extinct volcano craters often become flooded
themselves and form lakes, or
maars
; one of the biggest is Öskjuvatn in the Askja
caldera, but there are also smaller examples at Grænvatn on the Reykjanes Peninsula
and Kerið crater near Selfoss.
Thermal springs and geysers
Thermal springs
are found all over Iceland, sometimes emerging at ground level literally
as a hot-water spring - such as at Hveragerði - or flooding natural depressions or
crevasses to form hot pools, which can be found at Mývatn and Landmannalaugar. In
some cases the water emerges from the ground as steam through a vent; where this
mixes with clay, boiling mud pits or
solfataras
are formed, of which the most extensive
are those at Hverarönd, east of Mývatn. Natural steam is harnessed in Iceland to drive
turbines and generate
geothermal
power
, and also as heating for homes and hothouses.
While geysers tap into the same subterranean hot water as thermal springs, nobody is
quite sure exactly why they erupt - it's either a gradual buildup of water pressure or a
subterranean hiccup. Since the Krísuvík geyser blew itself to pieces in 1999, Iceland's
only example of note is at Geysir, northeast of Selfoss.
Glaciers, rivers and lakes
Glaciers
can be thought of as giant, frozen rivers or waterfalls that move downhill
under their own colossal weight. Usually movement is slow - maybe a few centimetres
a year - though some can shift a metre or more annually. In Iceland, they're all
associated with ice caps, the biggest of which,
Vatnajökull
(which more or less means
Glacial Sea), spreads over 150km across the country's southeast. These caps sit atop
plateaux, with a few isolated rocky peaks or
nunataks
poking through the ice, off which
scores of glaciers descend to lower levels.
Deeper glacial ice is often distinctly blue, caused by the air being squeezed out from
between the ice crystals by the weight of the ice above. However, glaciers are also full of
