<P> The shield stage of the volcano is subdivided into three phases: the submarine, explosive, and sub aerial . During this stage of growth, the volcano accumulates about 95 percent of its mass and it takes on the "shield" shape that shield volcanoes are named for . It is also the stage where the volcano's eruptive frequency reaches its peak . </P> <P> As eruptions become more and more frequent at the end of the preshield stage, the composition of the lava erupted from the Hawaiian volcano changes from alkalic basalt to tholeiitic basalt and the volcano enters the submarine phase of the shield stage . In this phase, the volcano continues to erupt pillow lava . Calderas form, fill, and reform at the volcano's summit and the rift zones remain prominent . The volcano builds its way up to sea level . The submarine phase ends when the volcano is only shallowly submerged . </P> <P> The only example of a volcano in this stage is Lō ʻihi Seamount, which is currently transitioning into this phase from the preshield stage . </P> <P> This volcanic phase, so named for the explosive reactions with lava that take place, begins when the volcano just breaches the surface . The pressure and instantaneous cooling of being underwater stops, replaced instead by contact with air . Lava and seawater make intermittent contact, resulting in a lot of steam . The change in environment also engenders a change in lava type, and the lava from this stage is mostly fragmented into volcanic ash . These explosive eruptions continue intermittently for several hundred thousand years . Calderas continually develop and fill, and rift zones remain prominent . The phase ends when the volcano has sufficient mass and height (about 1,000 metres (3,000 ft) above sea level) that the interaction between sea water and erupting lava fades away . </P>

Volcanoes eventually grow to become a chain of islands called an