The colors show the ages of the volcanic rocks that make up the island. This figure shows the position of the Mid-Atlantic Ridge (plate boundary) on Iceland. Iceland began to emerge from the sea about 16 million years ago, when enough lava had accumulated to raise the pile that high. Since then, the North American plate has moved to the northwest until the hot spot was under its current location beneath the Vatnajökull ice field (0 million years ago). Fifty million years ago, Greenland was over the hot spot. Keep in mind that hot spots remain stationary while plates move over them. The orange numbered circles on the map above-numbers are millions of years ago-show points under the North American plate where the hot spot was located during the past 50 million years. It is not at the boundary between plates but in the middle of a plate (Pacific), so it is only partly like Iceland. Hawaii is the classic example of a hot spot volcano. For more information about hot spots, see my post: ). So why has Iceland grown so much taller? That’s because it is also sitting on a hot spot-a hot plume bringing heat and molten rock (i.e., magma) from deep within the earth. The thing is-nearly all of these ridges are located about 2500 meters (8200 feet) beneath the ocean surface. As two plates pull away from each other, hot magma rises and erupts to form volcanic rock. Mid-ocean ridges are where ocean crust is created around the world. As the plates move apart, the Atlantic Ocean continues to widen at a rate of about 2 cm/yr (1 inch/year). The tectonic plates include both continents and the newly-created oceanic crust. Iceland sits on the Mid-Atlantic Ridge (pink lines, dashed where transform faults connect ridge segments), where the North American plate is separating from the Eurasian plate (green arrows) and new ocean crust (blue color) is being created. It was Norwegians who first settled the island in the year 840. This Google Earth map shows the location of Iceland in the North Atlantic Ocean between Greenland and Norway. This post describes the tectonic setting of Iceland the second post will explain the types of volcanoes and the third post will discuss the glaciers and their often-spectacular interactions with volcanoes. During a trip there with other geologists in July, I explored the landscapes of one of the most geologically-active places on our planet. Visiting Iceland is on pretty much every geologist’s “bucket list” because of its unique above-water position on a plate boundary where two plates are moving apart from each other (i.e., diverging). At its deepest, it is 63 metres.Sitting in the middle of the North Atlantic Ocean is the island country of Iceland. The Silfra fissure has three distinct sections: Silfra hall, Silfra cathedral – a 100 metre-long fissure with visibility almost from end to end – and Silfra lagoon.
This lengthy filtration accounts for the water’s purity. But after an eruption of the Skjaldbreiður blocked the river, water has trickled underground into porous lava rock and takes up to 100 years to travel to the lake. Until a few thousand years ago, meltwater ran through a river directly into the lake. The lake is also noted for its crystal clear waters, which are fed by Iceland’s second largest glacier Langjökull, about 50 kilometres to the north. Þingvallavatn is the country’s largest lake with an area of 83.7 square kilometres, and Silfra is a popular scuba diving attraction. They result in further cracks and fissures, but none are as large as Silfra. This movement, which builds up pressure in the earth above the crack, results in a major earthquake every 10 years or so. The Silfra fissure, under Þingvallavatn lake in Iceland’s Þingvellir, or Thingvellir, valley was formed as the Eurasian and North American tectonic plates move apart by around two centimetres a year.
0 kommentar(er)
