Examples of Hotspot Volcanism
Hotspots Under Oceanic Lithosphere
The Hawaiian Islands
These volcanic islands were formed from a hot spot that has occurred in the middle of the pacific plate, making it geologically significant. The Hawaiian Archipelago islands have been created here by undersea volcanoes building up to the surface, which formed by low viscosity lava eruptions (known as Hawaiian eruptions) which solidified to form shield volcanoes. . Over millions of years the plate moves north-west over the hot spot and though the original volcano becomes extinct, a new one will form above the hot spot.
Kauai is the oldest of the main Hawaiian islands now. It was formed about 5 million years ago. The volcano is now extinct and as an island it is in the process of being eroded. The youngest island of the Hawaiian Archipelago is the “Big Island” of Hawaii itself, with surface lavas all less than 1 million years old. It still has active volcanism, from its five volcanoes: Kohala, Mauna Kea, Mauna Loa, Hualalai and Kilauea. On the seafloor, 20 miles south east of Hawaii is an active volcanic area, a seamount called Loihi, which erupts periodically. It is estimated that it will take around 10,000 years before it breaks the ocean surface to form a new island.
The Hawaiian islands however, are not the only evidence of the hotspot that drives present day volcanism in the area. The Emperor range of Seamounts, reefs and Atolls stretches in a dog-leg shape Northwest of the present day location of the Hawaiian Islands, showing the motion of the Pacific plate in the same direction.
Kauai is the oldest of the main Hawaiian islands now. It was formed about 5 million years ago. The volcano is now extinct and as an island it is in the process of being eroded. The youngest island of the Hawaiian Archipelago is the “Big Island” of Hawaii itself, with surface lavas all less than 1 million years old. It still has active volcanism, from its five volcanoes: Kohala, Mauna Kea, Mauna Loa, Hualalai and Kilauea. On the seafloor, 20 miles south east of Hawaii is an active volcanic area, a seamount called Loihi, which erupts periodically. It is estimated that it will take around 10,000 years before it breaks the ocean surface to form a new island.
The Hawaiian islands however, are not the only evidence of the hotspot that drives present day volcanism in the area. The Emperor range of Seamounts, reefs and Atolls stretches in a dog-leg shape Northwest of the present day location of the Hawaiian Islands, showing the motion of the Pacific plate in the same direction.
Hotspots Under Continental Crust
The Deccan Traps
The Deccan traps are another example of hot spot volcanic activity, though present at the plate boundary rather than in the middle of a plate. Formation occurred around 65 million years ago, when a new mantle plume reached the surface and erupted- covering an area of 1.5 million square km with a thick layer of lava, that now is visible as over 2000m of flat lying basalt and covers an area of 500,000 square km. This large eruption, which took place over a very short time geologically of 500,000 years, would have changed the global climate dramatically, possibly leading to the demise of the dinosaurs which also occurred around 65 million years ago. At this time, the Indian plate was present at the current site of Reunion Island, which is now the youngest island of the South-East to North-West trending hotspot chain, having separated about 160 million years ago from the African continent, opening the Indian Ocean.
The western Indian Ocean. The red arrow indicates the layout of the hot spot on the ocean floor and the Mascarene plateau on the east of the oceanic rift (red arrow starting on Reunion Island). The layout continues on the west of the rift with the Chagos Archipelago, the Maldives and Lakshadweep and finishes with the Deccan Traps. The layout was cut between 35 and 48 million years by the mid oceanic rift.
Photo from http://www.ipgp.fr/pages/0303081001.php?langue=1
Photo from http://www.ipgp.fr/pages/0303081001.php?langue=1
The Snake River Plain-Yellowstone Hotspot
The Snake River Plain-Yellowstone hotspot is one of the most prominent areas of hotspot induced volcanic activity under continental crust on earth. Responsible for volcanic activity in Idaho, Wyoming, Nevada and Oregon, Yellowstone is an excellent example of a highly active area of hotspot volcanism.
Accounting for over half of the Worlds’ geothermal features, as well as two thirds of its active geysers, these features- as well as the mud-pots, hot springs and fumeroles of the area, are an expression of the incredible geological processes at work here and the power of the Yellowstone hotspot. With heat flow of ~2,000 mWm-2 in Yellowstone itself, around 30 times the continental average, the hotspot is not only responsible for the extensive hydrothermal activity and past volcanic eruptions in the locality and beyond (the first silicate volcanic deposits thought to have resulted from the hotspot date from around 70 Mya and are found in the Yukon region of Canada), but also the topography of the area. The heating of the lithosphere above the hotspot, leads to it being more buoyant than the surrounding crust. As a result of this buoyancy and the underlying volcanic processes, the Yellowstone topography is far from static. The Yellowstone plateau itself has experienced a great deal of movement over geologically minute timescales. In the 56 years up to 1985 alone, the area experienced around a meter in uplift, followed by subsidence from then until the present day.
The tectonic movement of the North American plate relative to the Yellowstone hotspot is etched into the landscape of the park, the Snake River Plain and beyond. The South-Westerly progress of the North American plate can be inferred from the chain of volcanic features, such as Calderas, stretching North-West of the region to the Yukon Region of Canada.
Accounting for over half of the Worlds’ geothermal features, as well as two thirds of its active geysers, these features- as well as the mud-pots, hot springs and fumeroles of the area, are an expression of the incredible geological processes at work here and the power of the Yellowstone hotspot. With heat flow of ~2,000 mWm-2 in Yellowstone itself, around 30 times the continental average, the hotspot is not only responsible for the extensive hydrothermal activity and past volcanic eruptions in the locality and beyond (the first silicate volcanic deposits thought to have resulted from the hotspot date from around 70 Mya and are found in the Yukon region of Canada), but also the topography of the area. The heating of the lithosphere above the hotspot, leads to it being more buoyant than the surrounding crust. As a result of this buoyancy and the underlying volcanic processes, the Yellowstone topography is far from static. The Yellowstone plateau itself has experienced a great deal of movement over geologically minute timescales. In the 56 years up to 1985 alone, the area experienced around a meter in uplift, followed by subsidence from then until the present day.
The tectonic movement of the North American plate relative to the Yellowstone hotspot is etched into the landscape of the park, the Snake River Plain and beyond. The South-Westerly progress of the North American plate can be inferred from the chain of volcanic features, such as Calderas, stretching North-West of the region to the Yukon Region of Canada.
Hotspots in Iceland
Hotspot in Iceland
There is a hotspot of volcanic activity in Iceland owing to MOR spreading. The mid-ocean ridge system (MOR) wraps around the earth for more than 65,000km, with over 90% lying underneath the ocean thus most of its eruptions pass unnoticed. However, it rises above sea level in Iceland, with recent maps showing a narrow region of recent volcanic activity of about 10km, and often in places less than 1km wide.
Eyjafjallajökull eruption in 2010
Eyjafjallajökull is not of the MOR, and is an atypical volcano in that it has two discrete magmatic sources of different compositions involved, as opposed to one main one. The eruption was caused by meeting of the basalt magma, with other magma, that is largely silica-rich trachyandesite. Recent research at the University of Iceland has suggested that this type of volcano might be more typical of moderately active volcanoes, as opposed to most active volcanoes on earth. Being an extremely recent eruption, detailed and abundant accounts exist, to give the following description of chains of events, as an example of a volcanic eruption. On March 20th 2010, there was great seismic activity at Eyjafjallajokull volcano as well as emergence of a red cloud glowing above the vast glacier that covers the volcano. Fire fountains jetted from 12 vents on the volcano, reached as high as 100m (according to the Institute of Earth Sciences at the University of Iceland.) The volcano seemed to return to dormancy, then on April 14th it erupted, emitting clouds of ash that reached as high as 11,000
The link below shows live footage of the eruption, hosted by YouTube. http://www.youtube.com/watch?v=f1ztg0wUqKY
There is a hotspot of volcanic activity in Iceland owing to MOR spreading. The mid-ocean ridge system (MOR) wraps around the earth for more than 65,000km, with over 90% lying underneath the ocean thus most of its eruptions pass unnoticed. However, it rises above sea level in Iceland, with recent maps showing a narrow region of recent volcanic activity of about 10km, and often in places less than 1km wide.
Eyjafjallajökull eruption in 2010
Eyjafjallajökull is not of the MOR, and is an atypical volcano in that it has two discrete magmatic sources of different compositions involved, as opposed to one main one. The eruption was caused by meeting of the basalt magma, with other magma, that is largely silica-rich trachyandesite. Recent research at the University of Iceland has suggested that this type of volcano might be more typical of moderately active volcanoes, as opposed to most active volcanoes on earth. Being an extremely recent eruption, detailed and abundant accounts exist, to give the following description of chains of events, as an example of a volcanic eruption. On March 20th 2010, there was great seismic activity at Eyjafjallajokull volcano as well as emergence of a red cloud glowing above the vast glacier that covers the volcano. Fire fountains jetted from 12 vents on the volcano, reached as high as 100m (according to the Institute of Earth Sciences at the University of Iceland.) The volcano seemed to return to dormancy, then on April 14th it erupted, emitting clouds of ash that reached as high as 11,000
The link below shows live footage of the eruption, hosted by YouTube. http://www.youtube.com/watch?v=f1ztg0wUqKY