One of Earth's longest mountain ranges, the Mid-Atlantic Ridge bisects the Atlantic Ocean for 11,300 km (7,000 mi). But it is hidden from our view — except where it straddles a hot spot. The combined volcanic activity of the ridge and one hot spot have produced the world's largest volcanic island: Iceland.

Like a splitting seam, magma wells up at the ridge crest and adds to the spreading plates on either side, ever-so-slowly widening the Atlantic Ocean.

• Heat Below, Mountains Above
• As Plates Spread, Iceland Grows
• 1783 - Laki Erupts
• 1973 - Citizens Battle Heimaey's Lava