Here's some planets that are all-magma, all the time.
Good morning. Today is sextidi, the 6th of Nivôse, Year CCXXXI. We celebrate la lave, molten minerals from the planet's core.
There are two main types of surface lava flow. The most common is ‘a‘ā – from the Hawaiian word for fire – that flows fast, hard, and far. This is the kind that leaves jagged little black igneous rocks everywhere, known adorably among volcanologists as "clinkers." The less common but more often photographed is called pāhoehoe – from the Hawaiian word for paddling – and flows very slowly, forming interesting contours as it slowly crusts over then seeps through again. You can see ropes, waves, "toes," or even elephant skin in pāhoehoe, but all of it is smoother than ‘a‘ā.
Lava is cool. Well, no it isn't, it's very hot, don't touch, but it's ... awesome. There's something mind-blowing about metal becoming so hot that it flows like water.
We only get to see magma once in a while, when a volcano gives us a little gift (that usually comes with the strings attached of death and destruction, but never mind that right now). But lava is everywhere! The best estimate is that 80 percent of the planet is made of lava (when you count the sea floor).
But what about planets that are 100 percent? We've found some. Here's a list: