Iceland: The Secret Of Its Creation Revealed

Along the entire length of the mid-Atlantic ridge at only one place has a landmass arisen from the ocean depths. At that place is where what we know as Iceland is located.

This begs the question, why here? Why at no other place along the mid-Atlantic ridge has a landmass formed?

A Clue: Analysis of the Igneous Rocks

The lava that is extruded from the mid-Atlantic ridge on the ocean floor is basaltic in composition, which means it has a high concentration iron and magnesium along with calcium-rich plagioclase feldspars and is very low in silica content. But when igneous rocks were collected in fissures left by fissure eruptions along the mid-Atlantic ridge in Iceland and were taken back to the lab for analysis something startling was discovered. The elements lanthanum and cesium were found to be present in the rock samples, from which can be inferred that the source of this magma was coming from greater depths than previously thought by geologists. Lanthanum and cesium, being two of the heavier rare earth elements on the Periodic Table of Elements, are normally only seen at great depths within the Earth’s interior, approximately 400 miles or more beneath the Earth’s surface, unless they are brought to the surface by magmatism and/or volcanism.

From this finding, in addition to the tremendous volume of lava that is extruded during one of these fissure eruptions on Iceland, geologists were able to infer that the source of this lava was coming from a heat source much deeper than previously thought.

The Island of Surtsey: A Second Clue

An aerial view of the island of Surtsey off the southern coast of Iceland.

The island of Surtsey, which arose from the depths of the Atlantic ocean just off of the southern coast of Iceland on November 14, 1963 is named after the Norse mythological figure Surtr (The fire demon or flame giant; known in old Norse as simply the black or swarthy one). I think Surtr (sometimes spelled, ‘Surtur’) over the centuries evolved in literature into the Norse god of Fire and Ice because of the Norse poem entitled Vafþrúðnismálin in which he is mentioned twice.

“Surtr moves from the south
with the scathe of branches:
there shines from his sword
the sun of Gods of the Slain.”

“rule over the possessions of the gods when Surt’s fire is slaked”.

It is the flaming sword of Surtr, shown in the two illustrations below, that I believe over time in people’s minds is what elevated this minor figure in Norse mythology to the status of the Norse god of Fire. But, Norse mythology is very complex, and I am no linguist.

"Surtr with the Flaming Sword" (1882) by Friedrich Wilhelm Engelhard. - Wikimedia Commons

Surtr: The painting "The Giant with the Flaming Sword" (1909) by John Charles Dollman. - Wikimedia Commons

The amazing thing about Surtsey is that it only took nine and a half months to form the island after it had finally broken through the surface of the Atlantic ocean on November 14, 1963. So clearly, some extraordinarily powerful source of heat must have been behind the creation of this island. The creation of Surtsey gave geologists a new insight into how Iceland itself must have formed some 20 million years earlier.

Ash column of the newly forming island, Surtsey. - Wikimedia Commons

The island of Surtsey as it appeared in 1999. - Wikimedia Commons

Seismic Waves: The Final Clue

In the science of seismology one is basically dealing with two types of waves, namely the P or primary waves and the S or secondary waves. There are other types of seismic waves, (e.g. Rayleigh waves, super shear waves, etc.), but for our purposes we need only concern ourselves with the P-wave and S-wave. P-waves, which are compressional waves and S-waves, which are shear or transverse waves, travel more slowly through hot or molten rock. It is this phenomenon that is of interest to us in our investigation.

Image credit: Encyclopaedia Britannica, Inc. © 2007

Normally, a seismograph will record a steady stream of S and P waves. But when the S and P waves travel through either hot or molten rock the readings change. Now in places like Hawaii and Yellowstone Park, where there is molten rock beneath the surface, you will see these changes in the readings.

Well guess what? When seismologists analyzed the seismic data coming from beneath Iceland, guess what they saw? That’s right! The same changes in seismic readings that are present in the seismograms of Hawaii and Yellowstone Park. And what do Hawaii and Yellowstone Park have in common? They are both sitting over hot spots.

A more comprehensive seismic analysis using artificially created seismic waves–a technique analogous to using ultrasound to see a fetus inside a mother’s womb–revealed a mantle plume or column beneath Iceland that spans about 100 miles in width and 400 miles in depth beneath the Earth’s surface.

So let’s take a look at all of the evidence and see what kind of a picture we can put together.

In the extrusive igneous rocks that were gathered from fissures and brought back to the lab and analyzed there was found lanthanum and cesium, which normally are only found at great depths in the Earth’s interior. The seismic data revealing the mantle column below Iceland corroborates the mineralogical findings that the heat source of the underlying magma and the extruded lava lies at great depths. The formation of Surtsey is evidence that the Atlantic plate has been moving over this hot spot for tens of millions of years.

So here’s the picture that geologists have come up with regarding the creation of Iceland. Given the rate of seafloor-spreading plus the overall movement of the Atlantic plate as a whole, it can be inferred that about 20 million years ago, as the Atlantic plate drifted towards the east, the mid-Atlantic ridge slid onto the mantle plume or hot spot where it is at the present time. The combination of the release of pressure by the mid-Atlantic ridge in conjunction with the tremendous heat (1700° F) generated by the mantle plume made for a one-two knockout punch.

This explains the inordinately prodigious rate of lava extrusion that made it possible for Iceland to not only have formed in the first place, but to have grown into the landmass that today encompasses 40,000 square miles! It also explains why one third of the world’s lava comes from Iceland.

And that ladies and gentlemen is the reason why Iceland is the only landmass that has formed along the entire length of the mid-Atlantic ridge. Mystery solved! 😉

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