The Iceland Hotspot

Robyn Brown

April 2011

ES 767 Global Tectonics
Emporia State University

A satellite view of the eruption of the Eyjafjallajökul Volcano in Iceland.
Image taken from NASA Image

Introduction

An underwater mountain chain known as the mid ocean ridge or the mid Atlantic ridge circles the globe and is one of the largest mountain ranges on Earth. The mid Atlantic ridge consists of underwater seamounts, volcanoes, and spreading ridges. However, at one location in the Atlantic, the mid ocean ridge rises above sea level. It cuts straight through the middle of one of the largest islands in Europe, Iceland. This makes Iceland one of the most geologically active places on Earth. Iceland is located east of Greenland in the middle of the North Atlantic Ocean. Iceland is around 20 million years old, which is rather young geologically speaking. Some of the most active volcanoes in the world are located in Iceland. This is due to Iceland remaining situated on a hotspot. A hotspot is an area under the crust that is relatively hot that receives energy from a thermal plume. Historical volcanism in Iceland provides more information on Iceland's volcanoes and their past eruptions.

A detailed map of Iceland lying in the middle of the Atlantic Ocean. It shows the mid Atlantic ridge cutting through Iceland along with the location of its hotspot. Image taken from Iceland Keck (Used by permission).


Origin of the Hotspot

The origin of the Iceland hotspot began with the breakup of the supercontinent Pangaea. As the Eurasian plate and the North American plate began to diverge, magma from underneath the crust rose up through the open rift and spilled over filling the valleys. This repeated activity of magma rising and cooling created the island of Iceland. Iceland was found to act more geologically complex than simple tectonic processes alone. Normal sea floor spreading and transform faults conflicted with the Icelandic tectonic processes. The crust underneath Iceland remained thin with a mantle plume that formed below the surface. A mantle plume or hotspot is a hot, narrow upwelling of molten material from the Earths mantle. The mantle plume hypothesis is popular among scientists which states portions of the mantle are hotter than average, thus melting the mantle. However, Iceland geology contradicted this hypothesis as research suggested that a shallow thermal plume existed. It takes greater depth to form a thermal plume as the process of a rising, spreading plume is unhurried. Although it was debated that the plume is not shallow, rather, it plunges deeper than scientists believed and it is just difficult to discern. Seismic tomography has taken place to study the mantle plume.


Three dimensional view of the mantle plume under Iceland.
Image taken from Iceland Plume (Used by permission)


Present Day Iceland

Iceland today is extremely active with volcanism and earthquakes. Three rift zones have appeared across Iceland in recent times. This is largely due to the spreading of the mid Atlantic ridge. The Eurasian and North American plates are still in the process of diverging and Iceland is moving with them. The portion of the crust located between two of the rift zones, called Hreppar in South Iceland, is departing with the North American plate. This will allow parts of Iceland that are active to eventually become inactive as it slides away from the hotspot. As Iceland moves, shifts in the spreading ridges occurs. One shift was discovered in North Iceland while a second shift is now in progress in South Iceland. Today, research indicates the Eastern Rift Zone slowly beginning to take over the Western Rift Zone and becoming the central spreading area in South Iceland. When a plate boundary has drifted a considerable distance a new rift zone develops. Rifting is no longer occurring in Central Iceland but has veered closer to 64 degrees North due to recent observations of constrained eruptions in the eastern zone. However, the western zone is still more seismically active than the eastern zone. It is estimated that the Western Rift Zone drifts 3.5 to 5 centimeters per year.


Present day map of Iceland. It is clear to see all three active rift zones, the northern, the western, and the eastern zone. The map also displays two rift zones to the west that are no longer active.
Image taken from Iceland Keck (Used by permission)


The Future of Iceland

Iceland will stay exceptionally active for many years to come. Iceland may eventually split as the Eurasian and North American plates proceed to diverge and the hotspot gradually cools off. Observation data obtained from a system called Project HOTSPOT will support further research as more sensors undergo installation around the thermal plume. Project HOTSPOT is an already existing system which consists of instruments that observe not only the seismical aspect but the gravitational and hydrological conditions as well. The goal of this network is to place it in the rigid environment of Central Iceland. In the future, more observation sites will increase over the area. These observation sites will allow more research to occur in areas that have bitter and harsh conditions. A website that is maintained by Richard M. Allen Project HOTSPOT explains in detail the purpose and goals of this program. To acquire a better understanding, access to a comparison data quality plot is available for viewing along with other interesting information concerning this project. Nonetheless, what the future holds for Iceland still remains a great geological mystery.


References

Asgeirsdottir, Margret 1999. The HOTSPOT Station observational networks in Iceland [Retrieved on April 14, 2011]

Einarsson, Pall 1991. Earthquakes and present-day tectonism in Iceland. Tectonophysics, 189, 261-279. Retrieved from http://www3.hi.is/~heidi/Data/Article-richard/Einarsson91.pdf [Retrieved on April 13, 2011]

Korenaga, Jun 2004. Large Igneous Provinces Commission International Associated of Volcanology and Chemistry of the Earth's Interior, Department of Geology and Geophysics, Yale University, The dynamics of the Iceland hotspot and continental breakup magmatism [Retrieved on April 13, 2011]

Korenaga, Jun 2004. Origin of the Iceland hotspot and the North Atlantic Igneous Province, Department of Geology and Geophysics, Yale University, Origin of the Iceland hotspot and the North Atlantic Igneous Province [Retrieved on April 13, 2011]

Ito, Garret, Mittelstaedt, Eric, van Hunen, Jeroen, 2011. Repeat ridge jumps associated with plume-ridge interaction, melt transport, and ridge migration Journal of Geophysical Research, Volume 116, PP. 20 [Retrieved on April 14, 2011]

Trønnes, R.G. Nordic Volcanological Institute, University of Iceland, Geology and geodynamics of Iceland [Retrieved on April 14, 2011]

Nolet, Guust, Morgan, Jason W., Vogfjord, Kristin, Allen, Richard M. 1997. Project HOTSPOT: A seismological study of the Iceland Hotspot Project HOTSPOT [Retrieved on April 28, 2011]


Figures and Illustrations

Illustration 1: http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=43912

Figure 2: http://people.usd.edu/~Brennan.Jordan/IcelandKeck2004.html

Figure 3: http://www.abc.net.au/science/news/img/iceplume.htm

Figure 4: http://people.usd.edu/~Brennan.Jordan/IcelandKeck.html