What happens if you fall into lava?

Molten basaltic lava has a density around 2,500 to 3,100 kilograms per cubic metre against roughly 1,000 for a human body, so anything falling onto it lands on top rather than sinking beneath. It is also far more viscous than water — the flowing rivers in footage move slowly and thickly for exactly that reason. Temperature is where the answer stops being interesting: basaltic lava erupts at roughly 1,100 to 1,200 °C, hot enough that the surrounding air causes severe burns before contact, and moisture in the body flashing to steam produces a violent reaction on contact. Volcano hazard agencies note that lava flows themselves cause relatively few deaths compared with other volcanic hazards, because they usually move slowly enough to walk away from; the fatal hazards are pyroclastic flows, lahars and volcanic gases.

The sinking-into-lava image comes from film. Lava is roughly three times denser than a body, so a person would land on the surface.

Physiology, not instruction. Every figure here is a population range under particular conditions, and individual variation is large — temperature, exertion, fitness and health move all of them substantially. Nothing on this page is medical advice.

Situations

• Can you survive a plane crash? Usually — across all US airline accidents studied, more than 95 per cent of occupants survived.
• How long do you have to escape a sinking car? Usually 30 seconds to a couple of minutes of floating — and the window is the way out, not the door.
• Can quicksand pull you under? No. Quicksand is roughly twice as dense as a human body, so you float — you sink to about waist depth and stop.
• How far from a nuclear blast do you have to be to survive? It scales with yield: for a one-megaton airburst, survival is unlikely within about 5 km and likely beyond about 10-12 km.
• How long can you survive in a hot car? Under an hour on a warm day for a child — the interior gains about 20 °C in the first ten minutes.
• How long does it take to drown? Under a minute to lose consciousness — and it is almost silent, which is why so many drownings happen in sight of others.
• What happens if a lift cable snaps? Essentially nothing — lifts hang from multiple ropes and have a speed-triggered brake that grips the rails.
• What height can you survive falling from? Survival is common below about 6 metres and rare above 20 — but people have survived falls from thousands.
• How likely are you to survive a shark attack? Very likely — of roughly 60 to 80 unprovoked bites worldwide each year, fewer than ten are fatal.
• What should you do if you are caught in a rip current? Rips pull you out, not under. Swim parallel to the beach until you are out of the flow, then come in.
• Could you survive inside a whale? You cannot be swallowed by almost any whale — their throats are too narrow — and a stomach offers no air.
• How long do you have to escape a burning house? Around three minutes from the alarm sounding in a modern furnished home.
• Can you survive a tsunami? Yes, by moving inland and uphill immediately — 30 centimetres of moving water can knock an adult off their feet.
• How long can you survive in a sealed container? Carbon dioxide becomes dangerous long before oxygen runs out — a few hours in a cubic metre of air.