Depositional formations found on the floor of caverns extending upward are called stalagmites.

Here's a breakdown:

* Stalactites: These formations hang down from the ceiling of a cavern. They are formed by the slow dripping of mineral-rich water.

* Stalagmites: These formations rise up from the floor of a cavern. They are formed by the accumulation of minerals deposited by dripping water.

When stalactites and stalagmites meet, they can form a column.