Magma undulates in the mantle, forming as the Earth’s plates collide.

      A man and woman collide
      in a café.  He pays for the coffee,
      and they share a table as they laugh
      and trade numbers.

Magma is less dense than the rock around it, and it begins to rise.

      As they leave, he rises from his seat
      and holds open the door, placing one hand
      on the small of her back. The skin
      under her thin cotton burns.

When magma erupts onto the surface of the Earth, it is called lava.  

      Months later they lie in bed, amid
      tangled sheets. The surface of their bodies
      hot to the touch. 

Sheets of lava flow over the ground; the lava eventually cools.

     She’s on her side, one hand on his chest,
     one leg on his. Their exposed limbs,
     once wet with sweat, begin to cool.

Cooled lava hardens and turns into basalt, pumice, or scoria.  

      On their 50th he gives her gold.
      She turns the ring on her finger,
      and feels the cool metal grow warm
      against her flesh.