I am so glad you are interested in lava – because it is the coolest!

I think the first part of understanding why lava is hot is to think about what lava actually is – melted rock!

All things have a melting temperature – that is, the temperature at which a solid material changes into a liquid. For example, the melting temperature of ice is 32° Fahrenheit. If ice gets warmer than 32° F, it changes from a solid (ice cube) to a liquid (water) – another way to say that is, it melts! And rocks do the exact same thing! If they get warm enough (hotter than their melting temperature) they will change from a solid (rock) to a liquid (lava). The difference between melting ice and melting rock is that rock has a MUCH hotter melting temperature than ice. That exact melting temperature depends on the type of rock, but most rocks deep in the Earth (where lava is formed) melt at temperatures as high as 2,000° Fahrenheit! So that is why lava is hot – because it only forms by melting rock at those really high temperatures.

Then, after the lava is erupted at a volcano, it is eventually cooled down by the air, and once it gets cooler than its melting temperature, it turns back into solid rock.