Travel Reference
In-Depth Information
Landscape and geology
Iceland's lunar landscapes are one of the country's prime attractions, but its
apparently ancient facade is in fact an illusion. Geologically, Iceland is very
young, with its oldest rocks dating back a mere fourteen million years, to a
time in the Earth's history when the dinosaurs had long gone and humans
were yet to evolve.
Iceland's landscape appears so raw because it sits on a geological hot spot on the
mid-Atlantic ridge, where the
Eurasian
and
American continental plates
are drifting east
and west apart from each other. As they do so, Iceland is continually tearing down the
middle, allowing
magma
(molten rock from the Earth's core) to well upward towards
the surface. When the surface cracks - in an earthquake, for instance - magma erupts
through as a volcano, and when groundwater seeps down to magma levels it boils and
returns to the surface as a
thermal spring
or, more dramatically, a
geyser
.
Almost all such geological activity in Iceland is located over this mid-Atlantic tear,
which stretches northeast in a wide band across the country, taking in everything
between the Reykjanes Peninsula, the Westman Islands and Mýrdalsjökull in the
southwest, and Mývatn and Þórshöfn in the northeast. As this band is where volcanoes
are creating all the new land, it's here that you'll find the most recent rocks; conversely,
the oldest, most geologically stable parts of the country are around Ísafjörður in the
West Fjords and Gerpir cliffs in Iceland's extreme east.
Iceland is also close enough to the Arctic for its higher mountains and plateaux
- most of which are in the south of the country - to have become permanently
ice-capped, forming extensive
glaciers
. Melt from around their edges contributes to
many of Iceland's
rivers
, which are further fed by
underground springs
- also the
source of the country's largest
lakes
. Cold, dry air formed by sub-zero temperatures
over the ice caps is also responsible for some of the weird
atmospheric effects
you'll
encounter here, whilst the
Aurora Borealis
or northern lights are caused by solar wind,
or streams of particles charged by the sun, hitting the atmosphere.
Volcanoes
Though Iceland's volcanoes share a common origin, they form many different types,
based on the chemical composition of their magma, which flows out of the volcano as
lava
. Where the lava is very fluid and the eruption is slow and continuous, the lava
builds up to form a wide, flattened cone known as a
shield volcano
, a type that takes its
name from the Skjaldbreiður (Shield-broad) volcano at Þingvellir. Where an eruption
is violent, the lava is thrown out as a fine spray, cooling in mid-air and forming cones
of ash or
tephra
, a cover-all name for volcanic ejecta; typical examples of tephra cones
are found at Mývatn's Hverfjall, and Eldfell on Heimaey in the Westman Islands.
Relatively rare in Iceland,
strato volcanoes
are tall, regular cones built from very
long-term lava and tephra accumulations; westerly Snæfellsjökull is a good example,
though the country's most consistently active volcano, Hekla, has formed in a similar
manner but along a line of craters rather than a single vent.
Crater rows
are one of the country's most common volcanic formations, caused when
lava erupts at points along a lengthy
fissure
, such as occurred at Leirhnjukur north of
Mývatn in the 1970s, and Lakagígar in southeast Iceland during the 1780s. Both
eruptions produced a string of low, multiple cones and large quantities of lava - in
Lakagígar's case, flows covered six hundred square kilometres.
Submarine eruptions
also
occur off Iceland and are how the Westman Islands originally formed, as demonstrated
