It takes just four hours for one bacterium to become .

256 bacterium.

Explanation:

suppose a bacterium would divide once in every half an hour, this means it would be double in half an hour.

therefore, a number of the bacterium after half an hour will be 1 x 2 = 2.

After one hour, we would have doubled the number of bacterium =2 x 2

= 4.

Also, in one and a half hours, it would become 4 x 2

= 8.

In 2 hours, it would be 8 x 2 = 16.

Also in two and half hours, it would  be 16 x 2

= 32.

In three hours, it would be 32 x 2

= 64.

In three and a half hours, it would be 64 x 2

= 128.

Funally, in four hours, the number of bacterium would have been multiplied to 128 x 2

= 256.

volcanoes (an event in the geosphere) release a large amount of particulate matter into the atmosphere. these particles serve as nuclei for the formation of water droplets (hydrosphere). rainfall (hydrosphere) often increases following an eruption, stimulating plant growth (biosphere).