"the Mid-Atlantic Ridge ... zone in which the floor of the Atlantic, as it keeps spreading, is continuously tearing open and making space for fresh, relatively fluid and hot sima [rising] from depth." - Alfred Wegener (1912)
The picture above shows the Mid-Atlantic (Ocean) Ridge (MAR) in Iceland's Þingvellir National Park. The MAR is a divergent plate boundary at which the Eurasian and the North American plates diverge (in the North Atlantic). A deep rift valley (underwater mountain system) shows the boundary between the two tectonic plates - created by magma rising to the seafloor via convection currents and erupting as lava and producing new rock - mainly basalt and gabbro - for the plates.
MAR and the hotspot - Iceland
The ridge is approximated to diverge by 2.5 cm every year (slow in comparison to the Pacific region, where the spreading rate is approximately 12 cm a year). Slow spreading ridges such as the MAR generally have wide rift valleys of 10 to 20 km. The part of the ridge on which Iceland is located is called the Reykjanes Ridge, after the Reykjanes peninsula in the southwest of Iceland. However, the MAR alone does not explain why Iceland is an island while all other parts of the ridge consist of mountains below sea level - another factor has to be important. The reason for Iceland being what it is, lies in it being located in a region with a higher temperature than the surrounding mantle as well as there being a higher concentration of water. Therefore the water in the magma reduces the melting temperature and this enhances volcanic activity on the island. Geologists are yet unsure about whether the hotspot is produced by a deep mantle plume or whether it originates at shallower depth. Unlike the Hawaiian hotspot, no progressive volcanic track caused by plate movement can be found at the Icelandic hotspot. Generally however, the deep mantle plume seems to be the more believable theory with scientists. Estimates to the depth and width of this possible have been found, it is also suggested however, that the hotspot is not hotter enough than its surroundings, to drive a plume. This ridge, together with the hotspot on which Iceland lies, are the key factors to why volcanic and seismic activity takes place in Iceland.
The map above shows how Iceland is located on the MAR. The red triangles indicate active volcanoes - they are all located ON the MAR.
The map above shows how Iceland is located on the MAR. The red triangles indicate active volcanoes - they are all located ON the MAR.
When the ridge system was discovered in the 1950s and the theory of seafloor spreading was introduced in the 1960s, Alfred Wegener's (forgotten) theory of continental drift (1912) was finally acccepted. In addition to that, scientists now believed in the expansion via plate tectonics. The idea of seafloor spreading due to plate tectonics marked a major historical change in geology, as this was the only way to explain and justify the extent of the massive build known as the mid-ocean ridge. When geologists accepted plate tectonics, the idea was seen as a "paradigm shift" - a term coined by US philosopher Thomas Kuhn, defining it as "a change in the basic assumptions or paradigms within the ruling theory of science" in geological thinking. It is now known that the motion of the continents is linked to seafloor spreading.
The Mid-Atlantic Rise is a geological feature described as a bulge running along the floor of the Atlantic Ocean. It is assumed that this bulge is formed by upward convective forces in the asthenosphere pushing the oceanic crust and lithosphere together. Therefore, the youngest rocks form at the axis of the ridge. Nonetheless, all rocks of the oceanic crust are much younger than the Earth itself, as they have only been around for less than 200 million years. Seafloor spreading occurs at mid-ocean ridges where new oceanic crust is formed through volcanic activity and then moves away from the ridge with time, as new rock is being formed constantly. Approximately 4km3 of new ocean crust are formed every year along mid-ocean ridges. Hess' theory states that new seafloor is formed when magma rises up.
The Mid-Atlantic Rise is a geological feature described as a bulge running along the floor of the Atlantic Ocean. It is assumed that this bulge is formed by upward convective forces in the asthenosphere pushing the oceanic crust and lithosphere together. Therefore, the youngest rocks form at the axis of the ridge. Nonetheless, all rocks of the oceanic crust are much younger than the Earth itself, as they have only been around for less than 200 million years. Seafloor spreading occurs at mid-ocean ridges where new oceanic crust is formed through volcanic activity and then moves away from the ridge with time, as new rock is being formed constantly. Approximately 4km3 of new ocean crust are formed every year along mid-ocean ridges. Hess' theory states that new seafloor is formed when magma rises up.
The divergent Mid-Atlantic Ocean Ridge was formed in the first period of the Mesozoic era - the Triassic, when a series of three-armed grabens (a block of land being downthrown which can produce a rift valley, as in this case) combined on the supercontinent Pangaea to form the ridge. The North Atlantic Ocean was created due to a failed rift arm (aulacogen) of the triple junction mentioned above. Therefore, it did not open uniformly. Rifting first began in the north central Atlantic whereas the South Atlantic only opened during the Cretaceous (145 - 66Ma).
The Mid-Oceanic Ridge is the longest mountain range in the world (65 000km) and a constantly geologically active area, due to its movement.
Geysers
Strokkur Geyser erupting, private picture, 2012
Strokkur, Iceland
The Strokkur Geyser is located in the southwest of Iceland, east of the capital Reykjavik and belongs to the Haukadalur geothermal area which includes mud pools, fumaroles, hot springs, algal deposits and geysers. It erupts every 3 to 8 minutes with a plume of approximately 20m. Because Iceland is located on the MAR and the Iceland hotspot, it is prone to earthquake and volcanic activity which therefore leads to hot springs including the rare phenomena of geysers.
Together with the Great Geysir (50m north of the Strokkur) which now erupts very infrequently after having been dormant for several decades, they are not only very popular tourist attractions but also beneficial to mankind.
Beneficial history of geysers
Already in the Paleolithic era (2.6 million years ago until 10 000 BP), geyser water was used for bathing and the Ancient Romans used them for heating. The Strokkur geyser in Iceland first erupted in 1789 when an earthquake along the MAR unblocked its conduit. In the 19th century, its activity often fluctuated but in 1815, the Strokkur spit water of 60m into the air. An earthquake blocked its canal again at the beginning of the 20th century and it never unblocked itself again naturally, so the community decided to have it cleaned out in 1963. Ever since, the Strokkur has been erupting regularly, after having been through several periods of dormancy.In the 1950s, Iceland was known to have approximately 30 known active geysers, however, this value does not account for unknown numbers and is likely to have changed since then.
The Strokkur Geyser is located in the southwest of Iceland, east of the capital Reykjavik and belongs to the Haukadalur geothermal area which includes mud pools, fumaroles, hot springs, algal deposits and geysers. It erupts every 3 to 8 minutes with a plume of approximately 20m. Because Iceland is located on the MAR and the Iceland hotspot, it is prone to earthquake and volcanic activity which therefore leads to hot springs including the rare phenomena of geysers.
Together with the Great Geysir (50m north of the Strokkur) which now erupts very infrequently after having been dormant for several decades, they are not only very popular tourist attractions but also beneficial to mankind.
Beneficial history of geysers
Already in the Paleolithic era (2.6 million years ago until 10 000 BP), geyser water was used for bathing and the Ancient Romans used them for heating. The Strokkur geyser in Iceland first erupted in 1789 when an earthquake along the MAR unblocked its conduit. In the 19th century, its activity often fluctuated but in 1815, the Strokkur spit water of 60m into the air. An earthquake blocked its canal again at the beginning of the 20th century and it never unblocked itself again naturally, so the community decided to have it cleaned out in 1963. Ever since, the Strokkur has been erupting regularly, after having been through several periods of dormancy.In the 1950s, Iceland was known to have approximately 30 known active geysers, however, this value does not account for unknown numbers and is likely to have changed since then.
Advantages
Although situated close to the North Pole, Iceland is one of the hottest places on Earth – beneath the ground we stand on, leading to the hot springs and geysers mentioned. These areas of intensive heat are beneficial to us in several ways, although they do have disadvantages as well.
In and around Reykjavik especially, geyser steam and hot springs are used to warm greenhouses for tomatoes, bananas and other tropical fruits which would otherwise need to be imported to an even greater extent.
Geothermal Energy
As the areas where geothermal energy can be produced are limited to tectonic plate boundaries and active volcanic areas, Iceland has a great advantage in the generation of geothermal energy and the production of electricity. Geothermal energy is defined as the heat from Earth’s core used to create energy – it arises from the Greek terms ‘geo’ for Earth and ‘thermos’ for heat.
Although Iceland has only approximately 30 active geysers (1950), five major geothermal power plants make use of the heat created and produce approximately 30% of the country’s energy, followed by the Philippines with 27% and El Salvador with 25% of national geothermal energy. Only 0.1% of the country’s energy is generated from fossil fuels. Nonetheless, it wants to become a nation with 100% fossil fuel free use in the near future.
In Iceland, the population has access to relatively inexpensive hot water, heating and electricity, due to the large amount of geothermal power generated at five major geothermal power plants – four of which are located in the same area (SW Iceland).
Geothermal power is both efficient and sustainable, which makes geothermal energy so important in terms of decreasing the pollution of the Earth’s atmosphere. Fossil fuels are not needed to generate electricity because the heat heat which comes from hot springs is used instead.
Replacing Fossil Fuels
Geothermal wells release greenhouse gases trapped in the Earth but at a much lower emission than the combustion of fossil fuels does. Therefore, in the future, geothermal power may help mitigate global warming if a way is found to replace fossil fuels with it worldwide.
The erection of geothermal power plants is generally less expensive than those of oil, gas, nuclear or coal power plants. Unlike the sources just mentioned, geothermal energy doesn’t directly contribute to global pollution. It is therefore beneficial to both the environment and the economy.
In and around Reykjavik especially, geyser steam and hot springs are used to warm greenhouses for tomatoes, bananas and other tropical fruits which would otherwise need to be imported to an even greater extent.
Geothermal Energy
As the areas where geothermal energy can be produced are limited to tectonic plate boundaries and active volcanic areas, Iceland has a great advantage in the generation of geothermal energy and the production of electricity. Geothermal energy is defined as the heat from Earth’s core used to create energy – it arises from the Greek terms ‘geo’ for Earth and ‘thermos’ for heat.
Although Iceland has only approximately 30 active geysers (1950), five major geothermal power plants make use of the heat created and produce approximately 30% of the country’s energy, followed by the Philippines with 27% and El Salvador with 25% of national geothermal energy. Only 0.1% of the country’s energy is generated from fossil fuels. Nonetheless, it wants to become a nation with 100% fossil fuel free use in the near future.
In Iceland, the population has access to relatively inexpensive hot water, heating and electricity, due to the large amount of geothermal power generated at five major geothermal power plants – four of which are located in the same area (SW Iceland).
Geothermal power is both efficient and sustainable, which makes geothermal energy so important in terms of decreasing the pollution of the Earth’s atmosphere. Fossil fuels are not needed to generate electricity because the heat heat which comes from hot springs is used instead.
Replacing Fossil Fuels
Geothermal wells release greenhouse gases trapped in the Earth but at a much lower emission than the combustion of fossil fuels does. Therefore, in the future, geothermal power may help mitigate global warming if a way is found to replace fossil fuels with it worldwide.
The erection of geothermal power plants is generally less expensive than those of oil, gas, nuclear or coal power plants. Unlike the sources just mentioned, geothermal energy doesn’t directly contribute to global pollution. It is therefore beneficial to both the environment and the economy.
Other advantages
Blue Lagoon, Iceland
Another use of geysers is the removal of H3BO3 (weak but toxic boric acid) from volcanic mud by the use of geyser steam. With this steam, cauldrons in which the mud has been put, are heated, which separate the boric acid from the volcanic mud due to different melting and boiling points.
It is also possible to bathe in some of the natural hot mineral springs, not in (dormant) geysers however. An example of this is the Blue Lagoon which is a geothermal spa ‘powered’ by the nearby Svartsengi Power Station. It is known to help cure dandruff and several skin diseases as well, due to the mineral-rich water.
It is also possible to bathe in some of the natural hot mineral springs, not in (dormant) geysers however. An example of this is the Blue Lagoon which is a geothermal spa ‘powered’ by the nearby Svartsengi Power Station. It is known to help cure dandruff and several skin diseases as well, due to the mineral-rich water.
Disadvantages
The areas where ‘natural’ geothermal energy can be produced is unfortunately limited to tectonic plate boundaries and active volcanic areas. In other parts of the world, the geothermal power needs to be produced via extraction of hot water from the Earth’s inner part rather than the hot water being close to the Earth’s surface already. Similarly, cold water can be pumped INTO the ground which is then heated, making the water rise back to the surface, where the heat is then collected and used to produce electricity. However, this is a more expensive and lengthy process than making use of the natural heat sources.
The location of geothermal power plants is difficult as well. This is because natural sources of geothermal energy are located along plate boundaries with volcanic activity. However, no one would want to build their power plant near a volcano. In addition, what must be remembered is that geothermal energy cannot be transported over long distances. Therefore, geothermal power plants need to be built close to populated areas as well.
Along with the geyser steam used to generate electricity, hydrogen sulfide can be formed. However, this highly toxic compound is very harmful and also very difficult to dispose of safely.
It has been claimed that the supply of water to the geothermal areas is not endless and that this way of making energy may prove to be unsustainable if a particular location is exploited too vigorously. Theoretically, no matter how possible this is, it is very unlikely that suddenly all volcanic and seismic activity in a particular location (especially in Iceland, at the divergence of two boundary plates) halts at the same time and leaves the country without means to produce geothermal energy.
The location of geothermal power plants is difficult as well. This is because natural sources of geothermal energy are located along plate boundaries with volcanic activity. However, no one would want to build their power plant near a volcano. In addition, what must be remembered is that geothermal energy cannot be transported over long distances. Therefore, geothermal power plants need to be built close to populated areas as well.
Along with the geyser steam used to generate electricity, hydrogen sulfide can be formed. However, this highly toxic compound is very harmful and also very difficult to dispose of safely.
It has been claimed that the supply of water to the geothermal areas is not endless and that this way of making energy may prove to be unsustainable if a particular location is exploited too vigorously. Theoretically, no matter how possible this is, it is very unlikely that suddenly all volcanic and seismic activity in a particular location (especially in Iceland, at the divergence of two boundary plates) halts at the same time and leaves the country without means to produce geothermal energy.