Which type of cave forms the fastest?

Lava tubes form the fastest among the options listed due to their formation process related to volcanic activity. When lava flows from a volcano, it can create a hard outer layer as the surface cools while the molten lava underneath continues to flow. As the flow of lava eventually ceases and drains away, it leaves behind a hollow tube.

This process can occur relatively quickly in geological terms, often within a matter of days to weeks, leading to the rapid formation of caves. In contrast, the formation of other types of caves, such as coral reefs, sea caves, and sandstone caves, typically involves much longer processes. Coral reefs develop slowly through biological activity, sea caves are shaped by the gradual erosion of rock by wave action, and sandstone caves form through weathering and erosion processes that take thousands to millions of years. Thus, the rapid formation of lava tubes distinguishes them as the fastest type of cave formation among the listed options.