Iceland: Living on a Mid-Ocean Ridge: L. Carboni-Gorbea and T. Brandon
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Iceland: Living on a Mid-Ocean Ridge
By: Livia Carboni-Gorbea and Timothy Brandon
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What is a Mid-Ocean Ridge?
- Mid-Ocean Ridges are where two plates are pulling apart from each other as hot magma (liquid rock) emerges from the mantle as lava to fill the crack continuously created by the plate separation. The lava cools and attaches itself to the trailing edge of the plate, forming new ocean floor crust in a process commonly known as sea-floor spreading.
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The Mid-Atlantic Ridge (Iceland)
- Iceland is geologically young land; Iceland is located on both a geological hot spot, thought to be caused by a mantle plume, and the Mid-Atlantic Ridge, which runs right through it.
- The Mid-Atlantic Ridge is a submerged mountain range that extends from the Arctic Ocean to beyond the southern tip of Africa, but is only one segment of the global mid-ocean ridge system that encircles the Earth.
- This is the only place where a mid-ocean ridge comes to the surface in its entirety and as such offers a unique opportunity to study its structures and the volcanism that are associated with it. Eruptions occur every 5-10 years and so there is always something new. Earthquakes are a regular occurrence and their effects may be seen in the landscape. Because the land forming processes are so active this is an ideal place to study surface processes and to contrast the results so easily.
- The average spreading rate along the Mid-Atlantic Ridge averages about 2.5 centimeters per year (cm/yr), or 25 km in a million years. This process has been going on for millions of years, and has resulted in plate movement of thousands of kilometers. Over the past 100 to 200 million years the Atlantic Ocean has grown from a tiny inlet of water between the continents of Europe, Africa, and the Americas into the vast ocean that exists today.
- The island itself is composed of primarily of basalt, low silica lava that is native to a Mid-Ocean ridge, also associated with effusive volcanism like Hawaii. There are, however, a variety of volcano types on Iceland that produce more evolved lavas such as rhyolite and andesite.
- Iceland controls Surtsey, one of the youngest islands in the world. It rose above the ocean in a series of volcanic eruptions between November 8, 1963 and June 5, 1968.
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The Effects of the Mid-Atlantic Ridge (on Iceland)
- The consequences of plate movement are easy to see around Krafla Volcano, in the northeastern part of Iceland. Here, existing ground cracks have widened and new ones appear every few months. From 1975 to 1984, numerous episodes of rifting (surface cracking) took place along the Krafla fissure zone. Some of these rifting events were accompanied by volcanic activity; the ground would gradually rise 1-2 m before abruptly dropping, signaling an impending eruption. Between 1975 and 1984, the displacements caused by rifting totaled about 7 m.
- Because of the combination of the locations of hotspots and a Mid-Ocean Ridge, this means that geologically the island is extremely active, having many volcanoes, notable Hekla, Eldgjá, and Eldfell.
 Mount Hekla erupting in 1980. Seen from 4 km NE of the ":summit. |
 Lava fountains tower over Heimaey in the early stages of the Eldfell eruption |
- The volcanic eruption of Laki in 1783 – 1784 caused a famine that killed nearly a quarter of the island’s population. The eruption caused dust clouds and haze to appear over most of Europe and parts of Asia and Africa for several months after the eruption.
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