u/Express-Ad1108

Crafted from 9 blocks of regular magma, active magma naturally generates near the shores of the Nether's lava oceans and in Basalt Deltas.

When placed below lava, active magma will periodically shoot own geysers of lava that set on fire and push entities upwards. Similar to sulphur geysers, the height of the geyser is determined by the number of lava blocks above. However, unlike sulphur geysers, lava geysers give a prepararion sound and particles before activation to allow players to avoid them.

Lava above active magma produces bubbles.

Active magma is also the only solid block hot enough to keep Striders warm. And its damage to the players cannot be avoided with sneaking.

Additionally, active magma allows for infinite netherrack - when lava touches blue ice over active magma, it produces netherrack rather than basalt, making netherrack fully renewable.