Correct Answer: Option 4 – Explosive eruption of lava from a volcano

Pumice rocks are extrusive igneous rocks meaning it is formed by volcanic eruptions on the surface and typically created when super-heated, highly pressurized rock is violently ejected from a volcano. It can be formed when lava and water are mixed. They are generally produced from volcanoes whose lava is of a viscous type (less viscous lava produces the characteristic lava flows).

This igneous rock is light and porous, containing a network of gas bubbles in volcanic glass and minerals. Pumice has an average porosity of 90%, and initially floats on water. Pumice is commonly pale in color, ranging from white, cream, blue or grey, to green-brown or black. Pumice is a common product of explosive eruptions and commonly forms zones in upper parts of silicic lavas. It produced in very large quantities and may accumulate as lumps or as abraded fragments of pumice called shards. .

Based on these arguments, the rest of the options are incorrect.