Download 11. Jarðsaga Íslands og landmótun (e. Iceland`s geologic history

11. Jarðsaga Íslands og landmótun (e. Iceland’s geologic history)
 Hvað er Ísland gamalt?
 The earth’s history is about 4600 million years but the history of Iceland is only 16 million years,
which makes Iceland one of the youngest countries in the world.
 Two factors have played a major role in the formation of Iceland. One is that Iceland lies astride
the mid Atlantic ridge where the American and the European tectonic plates are constantly
moving apart,
 The second is that Iceland is a hot spot right above a mantle plume. This means that Iceland has
piled up through voluminous volcanic eruptions in fact Iceland is one of the most active volcanic
areas in the world.
 Hvernig leit landið út fyrir ísöld?
 Before the forces of Ice age started to form and shape the land, the landscape was rather
monotonous. It was mostly flat with volcanoes and lava spreads and because the weather was
warmer then than it is now, it was probably cowered with forest.
 The first ice age started about 3 million years ago. Ice ages last about 100 thousand years with
warm intervals of 10- 20 thousand years. The last ice age started 110 thousand years ago and
ended 10 thousand years ago.
 Steingervingar/rannsóknir
 We know this from studying stratum and fossils that can be found in Iceland’s oldest rocks at the
west and east of the country.
 These fossils cover all of Iceland’s geographical history. They are manly plant remains like leafs;
tree trunks and pollen (frjókorn) The oldest fossils that have been found are around 15 million
years old. The best-known place in Iceland where plant fossils have been found is in Brjánslækur
in Barðaströnd located at the south of the west fjords. From the fossils found there we know that
around 10 million years ago trees like walnut and maple used to grow here. But as the weather
grew colder at the beginning of the ice age, trees like conifers (barrtré) took over.
 The second most common fossils found in Iceland are shell fossils. These fossils can tell us about
the different position of sea level at different times in the lands history. The place where these
fossils are mostly found is at Tjörnes at the north east of Iceland.
 Not many animal fossils have been found in Iceland. The oldest animal fossil found a small deer,
is believed to be between 3-4 millj. years old. A few fossils of birds, sea animals and sea
mammals have also been found.
 While ice covered the land, volcanoes erupted under ice and formed palagonite mountains and
ridges. The ice was also a major force in forming fjords and valleys as it would move and dig
through softer stratum and rocks. The ice covered more of eastern Iceland than west Iceland.
Therefore the mountains at the east are pointier than the mountains at the west that have flat tops.
 As volcanoes erupted under ice glacial bursts rushed forth and formed ravines and gorges. When
the weather got warmer and rivers started flowing down these gorges, they would slowly widen
and form valleys. Icefalls and rivers especially glacial rivers move rocks, stones and sand from
one place to the other and change the land. As the glacier recedes lakes and glacial lagoons often
form.
 Two other forces also play an important role in forming the land. They are the weather with its
rain and often-strong winds and the sea, which constantly rasp the Icelandic shores.