What we can learn from a step on Lava : that's so dangerous because lava is so hot!
When the lava emerges from one of the vents at Kilauea, it comes out at 700 to 1,200 °C (1,292 to 2,192 °F), and begins to make its way to the path of least resistance.
This video shows how pressure applied to this dense material only causes a slight indentation. While this may not be surprising (it is liquid rock), I think that many people think of lava as more of a hot-watery-like substance. You would never fall into a lava lake the way you would a swimming pool, the molten rock is much more dense, so you would simply land on it, sink a little, and be burned.