As magma meets the water, it cools and solidifies, adding to the edges of the sideways-moving plates. as magma piles up along the crack, a long chain of mountains forms gradually on the ocean floor. this chain is called:

ANSWER:

As magma meets the water, it 'cools and solidifies', adding to the 'edges of sideways-moving plates' as magma piles up along the crack, a 'long chain of mountains' forms on the 'ocean floor', this process or the chain is called Seamount.

EXPLANATION:

When the magma cools or make contact to water than it starts to turn solid and it starts moving up the building blocks while cooling.Magma is a hot semi-fluid or fluid material which is found within or below the 'earth's crust' from which 'lava' and other 'igneous rock' is formed by process of cooling.

H=   2(area/a+b)h= 2(144/a+b)h= 2(144/18+18)h= 2(144/36)h= 2(4)h=8

Maybe a horizontal because its a pattern