lava tube
Molten rock conduit
A lava tube is a natural tunnel formed when the outer surface of a lava flow cools and hardens while molten lava continues to flow beneath, eventually draining and leaving a hollow passage.
These geological formations can extend for miles and range from small crawlspaces to caverns large enough to walk through.
Lava tubes occur on Earth and have been identified on the Moon and Mars, where they've attracted interest as potential sites for human habitation.
Large natural underground chamber
- chamberEnclosed room or cavity
- grottoSmall scenic cavern
- subterraneanBeneath earth's surface
- undergroundBelow ground or countercultural
darkness · skylight · entrance · passage · tunnel · ceiling · floor · collapse
Molten rock underground
- basaltFine-grained volcanic stone
- eruptionViolent sudden release
- ventOpening for airflow
- fissureNarrow crack in rock
shield volcano · effusive · Kilauea · Etna · volcanic · Hawaii · Iceland · Canary Islands
Sharp, blocky lava flow
- crustHard outer layer
- moltenLiquefied by extreme heat
- coolingLosing thermal energy
- solidificationTransition to firm state
channel · drainage · inflation · deflation · breakout · levee · roof · skin
cavern
Large natural underground chamber
- chamberEnclosed room or cavity
- grottoSmall scenic cavern
- subterraneanBeneath earth's surface
underground · darkness · skylight · entrance · passage · tunnel · ceiling · floor · collapse · drip
magma
Molten rock underground
fissure · shield volcano · effusive · Kilauea · Etna · volcanic · Hawaii · Iceland · Canary Islands · Galapagos
aa
Sharp, blocky lava flow
solidification · channel · drainage · inflation · deflation · breakout · levee · roof · skin · insulation
spelunking
Exploring caves recreationally
- cavingSport of exploring caverns
- headlampForward-facing vehicle light
- expeditionOrganized exploratory journey
adventure · torch · gear · ropes · harness · descend · crawl · traverse · pitch-dark · echo
- spacespace, sun, moon, stars, star
- cavescave, cavern, caves, caverns, grotto
- HawaiiHawaii, Pearl Harbor, Honolulu, Maui, Waikiki Beach
- volcanic activityeruption, active, dormant, magma, extinct
- volcanoesvolcano, volcanic eruption, Mount Fuji, volcanic eruptions, caldera
- island featuresbeach, lagoon, coral reef, atoll, reef
lava tubesubway tunnel
Underground rail corridor
mine shaft · railway tunnel · pedestrian tunnel · aqueduct · Channel Tunnel