dating, advances in petrology and geochemistry, advanced surveillance and monitoring, and detailed geological studies. The ratio of magnesium to silica in the lava is a sign of what stage the volcano is in, as over time the volcano's lavas shift from alkalic to tholeiitic lava, and then back to alkalic. Although volcanism and erosion are the chief factors in the growth and denudation of a volcano, other factors are also involved. Subsidence is known to occur. Changes in sea level, occurring mostly during the Pleistocene, have caused drastic changes; an example is the breakup of Maui Nui, initially a seven-volcano island, which was transformed into five islands as a result of subsidence. High rainfall due to the trade wind effect impacts on the severity of erosion on many of the major volcanoes. Coastline collapses, a notable part of the history of many of the Hawaiian volcanoes, are often devastating and destroy large parts of the volcanoes. Submarine preshield stage When a volcano is created near the Hawaiian hotspot, it begins its growth in the submarine preshield stage, characterized by infrequent, typically low volume eruptions. The volcano is steep-sided, and it usually has a defined caldera and has two or more rift zones radiating from the summit. The type of lava erupted in this stage of activity is alkali basalt. Due to stretching forces, the development of two or more rift zones is common. The lava accumulates in a shallow magma storage reservoir. Because the eruptions occur with the volcano underwater, the form of lava typically erupted is pillow lava. Pillow lava is rounded balls of lava that was given very little time to cool due to immediate exposure to water. Water pressure prevents the lava from exploding upon contact with the cold ocean water, forcing it to simmer and solidify quickly. This stage is thought to last about 200,000 years, but lavas erupted during this stage make up only a tiny fraction of the final volume of the volcano. As time progresses, eruptions become stronger and more frequent. The only example of a Hawaiian volcano in this stage is Kamaʻehuakanaloa Seamount (formerly Lōʻihi), which is thought to be transitioning from the submarine preshield stage into the submarine phase of the shield stage. All older volcanoes have had their preshield stage lavas buried by younger lavas, so everything that is known about this stage comes from research done on Kamaʻehuakanaloa Seamount.