#2 - The Underwater Volcanoes Driving Us Apart

If you are a South American living in Africa, or a European living in North America, your journey back to your home country is longer today than it was when you migrated across the Atlantic Ocean.

Every day, at the rate your fingernails grow, Europe moves ever-so-slightly away from North America, and South America edges away from Africa.

One of the products of this tectonic trudge? Underwater volcanoes!

Our ocean floors are alive

Standing on the southwest coast of the UK as a child, I imagined the vast Atlantic Ocean like a shallow-sided bowl, where the water got progressively deeper until you reached the middle.

But oceans aren't like the oceanic bowl I imagined. Ocean floors are alive with volcanoes and trenches in a geologic maze visible from space. 

You can sneak a peek at this oceanic labyrinth by looking at a satellite image of Earth, or bathymetric map showing ocean depth. Darker colors correlate with the deeper parts of our oceans, while lighter colors indicate shallower waters. 

The Atlantic Ocean's surprising shallows
One of these shallow areas occurs slap bang in the middle of the Atlantic Ocean. This meandering region of light blue, which stretches 16,000 km (10,000 miles) from the Arctic in the north to Antarctica in the south, represents the longest mountain range on Earth: The Mid-Atlantic Ridge.

The water is only about 2.5 km (1.6 miles) deep here; an oceanic paddling pool in comparison to the deepest parts of the Atlantic, which are over 3 times deeper.

The volcanic crevasses creating new ocean floor

The middle of the Mid-Atlantic Ridge is marked by a long, thin crevasse; visible on bathymetric maps as a dark blue stripe. Along the crevasse, volcanoes spew lava from Earth's innards and into the ocean.

Over time, the build up of lava creates new ocean floor in the middle of the Atlantic, which effectively pushes Europe away from North America, and Africa away from South America.

A weight off my shoulders: The lava production factory

Lava is generated by partially melting rock deep beneath the ocean floor. But how does solid rock melt?

Just like grapes grow in specific climates, lava is only produced under certain conditions. But rather than sunlight and water being the key controls, lava production needs the right blend of pressure, temperature and water.

The Mid-Atlantic Ridge Lava Farm principally owes its success to one variable: pressure.

Living our lives on Earth's surface, we are familiar with increasing temperature if we want to melt something. But down in the bowels of Earth, a significant reduction in pressure is just as effective at partially melting rock.

This is because temperature and pressure are explicitly linked: rocks experiencing lower pressures require lower temperatures to partially melt, while rock experiencing higher pressures needs higher temperatures to partially melt.

The area beneath the Mid-Atlantic Ridge is a uniquely low-pressure environment, enabling the production of the lava spewed out onto the ocean floor. 

The oceanic OAPs close to our shores

If brand new ocean floor is being created in the Mid-Atlantic Ridge, it follows that the age of ocean crust increases as we move further away from this lava production factory.

The newest additions to the ocean crust family sit in the middle of the Mid-Atlantic Ridge, while the oldest crust is found close to the shorelines of the surrounding continents: North America, Europe, South America and Africa.

These oceanic Old Age Pensioners have seen a lot in their 100-million-years (or more!) of existence. This wise old crust could tell us tales of T-Rex and Velociraptor, as well as the mass extinction event responsible for their demise 65 million years ago. 

What The Rock? The Underwater Volcanoes Driving Us Apart

The Atlantic Ocean is far more interesting that the shallow-sided oceanic bowl I envisaged as a child. It plays host to the longest mountain range on Earth: The Mid-Atlantic Ridge.

Here, underwater volcanoes create brand new ocean floor, which help to fuel the tectonic trudge of Europe away from North America, and Africa away from South America.

The heart of this continental engine is a lava production factory that owes its existence not to searing temperatures, as you might expect, but plummeting pressure. 

With thanks to: Oliver Ward for generously donating his time to help steer a very poor first draft towards something (hopefully) worth reading. 

Diana Armstrong's nails are not only a moving tribute to her daughter; they also represent the distance Europe has travelled from North America in 25 years (roughly!). 

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