* Volcanoes are dynamic: The amount of lava within a volcano changes constantly. Magma (molten rock underground) is constantly flowing, rising, and solidifying. Some volcanoes may be actively feeding lava flows while others are dormant with little to no magma.
* Magma chambers are complex: Magma chambers, where lava is stored, are not simple underground pools. They can be vast and interconnected, with branches and conduits. It's very difficult to accurately map their size and shape.
* Limited data: We can use various techniques (like seismic imaging) to estimate the size of magma chambers, but we lack the technology to get a complete and accurate picture of their contents.
Instead of a specific quantity, we can consider these factors:
* Volcano size: Larger volcanoes tend to have larger magma chambers and potentially more lava.
* Eruption history: Volcanoes that have had large eruptions in the past may have larger magma chambers than those with smaller eruptions.
* Volcanic type: Different types of volcanoes (shield, strato, etc.) have varying magma chamber configurations and eruption styles.
In summary, we can't give a specific amount of lava held by volcanoes. It's a constantly changing, complex system, and our understanding is constantly evolving.
