Lava, Falls and Cave Hazards

Lava is the single biggest killer while mining. Contact deals 4 damage roughly every half-second you're touching it, and it also sets you on fire for a further stretch that keeps ticking damage even after you've escaped it. An unarmored player lasts about 2.5 seconds standing in lava before dying; full sets of stronger armor buy more time, but even a complete, unenchanted set of netherite armor only stretches that to around 11 seconds. Any ordinary item that falls into lava is destroyed instantly, with only netherite-related items surviving the drop.

Lava spreads slowly in the Overworld, about one block every 1.5 seconds, but the block you're about to break into gives no warning beyond sound and, if it's directly above you, a faint dripping particle effect. That's exactly why experienced miners stop and listen for lava's crackle before committing to the next block, then approach it from an angle rather than head-on. Keeping a water bucket or a few spare blocks on hand lets you wall a lava pool off, or turn a source block to obsidian on contact, the moment one turns up.

The other classic mistake is vertical tunneling. Mining straight down risks dropping straight into an open cave, ravine, or lava pool below, with no chance to see what's coming or stop before you land in it. Mining straight up carries a similar risk from gravel or sand collapsing on top of you, or breaking into a space you never got to look at first. Staircasing down instead — one block forward, one block down, repeated — means you always see the next block before you commit to standing on it, which is the entire safety advantage over a blind vertical shaft.