Iceland's volcanic UNDERBELLY
How do oceans open and islands form? Follow Iceland's slow rise
to the surface from the widening floor of the Atlantic Ocean.
By Holly McKelvey
Steam leaks up in plumes and rivulets from fissures in the clay-cracked ground. Brick orange and lurid yellow soil gives way to pools of gray mud that belch and bubble. The sulfuric tinge of eggs clings inescapably to the air, clinging to the inside of the nose at first, fading into a background smell after the first few minutes. On the horizon soar mountains permanently capped with snow. Even at distance, the peaks are crystal clear.
We are standing on the rocky landscape of Iceland, a volcanic and bubbling hotspot of living geology perched atop the spreading plates of the mid-Atlantic. This is a geologist's playground, a source of natural wonder and a platform to observe the constant shifting mobility of the earth beneath our feet. It is also a land that powers and heats itself off the warmth of the earth.
Iceland caught the word's attention in 2010 when its volcano Eyjafjallajökull erupted, grounding flights and reminding us of the many ways in which the unpredictability of our planet's shifting crust holds sway over little human necessities like air travel. But its history began long, long before. Let's take a step back in time.
The year is 170,000,000 years before present (BP)*. In this moment, many tens of millions of years before the present day, the vast land blocks that we now call North and South America are beginning to split apart from Africa and the rest of the Pangean supercontinent. As the plates slowly split apart, new magma rises to the surface along the rifting boundary and hardens; the new material contributes to the newly separating plates as they slip away from one another. This happens gradually over tens of millions of years, forming first volcanoes, then a basin, then a sea. Picture, in its earliest days, the sunken relief of the East African Rift Valley, a landscape that is also beginning the snail's pace rifting process. This is the beginning of the Atlantic Ocean.
Jump forward to about 60 million years BP. The southern part of the Atlantic Ocean has opened, and a sea now lies between Africa and the Americas. The North Atlantic Ocean is just beginning to open, following the same gradual rifting process as the South Atlantic. Magma rises to the surface along the rift boundary, hardens, and creates new sea floor. As the Eurasian plate slides away from North American plate, it is spurred by an extra surplus of hot magma emerging from the mantle in one specific northerly spot. This extra input of magma weakens the Earth's lithosphere, making it easier for the two plates to slide apart and widen into the North Atlantic Ocean. This plume of magma? Spoiler alert: it's called the Iceland plume.
As the North Atlantic widens and fills in with water over the next tens of millions of years (geological timelines – notoriously slow), this spot above the Iceland plume grows higher, built up by the extra magma seeping up at that specific point and erupting in underwater volcanic events. Over time these underwater volcanoes rise above the surface of the young ocean. An island is born.
Jump back to the present. The island that is Iceland sits above the water now, spreading in an east-west direction. It is getting bigger each year, millimeter by creeping millimeter; the oldest parts are about 3 million years, the youngest less than 700,000 years old (baby-aged, in geological years). The evidence of this growth? Prominently, the volcanic eruptions, most recently the airplane-stopper of 2010. But Iceland reminds us it's still growing in a gentler sort of way as well: burbling hot springs, sulfuric mud pits, plumes of steam on a chilly landscape marking the geothermal vents Iceland uses to harness so much of its energy.
Each of these is a reminder that geology is a very active, very present force here, on this island perched atop the Atlantic rift boundary, where liquid magma from the mantle emerges faster than anywhere else along the plate boundary. Plate tectonics, a process that normally unfolds on a timescale far beyond a human lifespan, is observable here through the volcanic activity. As you sink into a hot spring or wrinkle your nose at the sulfuric smell – your senses are describing to you the history of the Atlantic Ocean gradually opening, and Iceland's slow volcanic rise out of the sea. A geological history in action.
* For reference, geologists mark 1950 as present, so when you see before present (BP) in academic articles, you can add the extra 65+ years to reach the actual present. When speaking about geological time, of course, 65 years is less than a blink, so the calculation isn't really necessary.
Holly is a graduate student in Environmental Management at the University of Kiel, Germany, where she cycles a lot, drinks tea, and enjoys the brief lapses of sunshine. She can be reached at firstname.lastname@example.org