Trigger

Trigger (起爆剤) is the name used to refer to the Small Scale Induction-Style Active Volcano Controlling Device (小規模誘発式活火山制御装置). It is a technology developed by the United States military for the purpose of inducing a controlled eruption of volcanoes. Though seemingly only a part of GREMLIN's plan, it later becomes clear that its purpose was greatly downplayed for the purpose of deception.

Appearance
Individual devices, which look like drums with four legs, which spread out like a cross and are then affixed to the ground securely with special stakes as support, are attached in strategic locations around a volcano. There are no cables, as each individual device are timer controlled, and a totally isolated system.

Principles
It was developed by the military and is primarily based in Oahu. As the name suggests, it is a device that control the activities of an active volcano. It's purpose is not to stop an eruption from occurring but to distribute the energy to minimize its destructive property of the sheer force of an eruption.

It uses a special combination of explosives set up in strategic points around an active volcano and apply stimuli in various stages to the underground magma to regulate it and cause small scale eruptions, hence the name. The device's stimuli is via sending powerful vibrations underground from multiple angles at once.

By letting the pressure escape before a major eruption occurs, the worse case scenario can be avoided. However, with proper manipulation, the technology can also be use to incite a destructive eruption.

Hawaii Invasion Arc
The Trigger plays an important role in the beginning of the arc, however, its full importance is revealed only at the end.

Roberto Katze, uses the Imperial Package to determine the queer circumstances surrounding his government. More importantly, the fact people unrelated to Trigger is somehow trying to find information regarding it. Later, he discovers that Trigger is Oahu, in Pearl Harbor. After joining Leivinia and Touma's group with Accelerator, they determined that GREMLIN's goal was to strike the United States of America (and by proxy the Science side), shaming it in international affairs and distablize its economy, by inducing an eruption of Kilauea, the largest volcano in the Hawaiian Islands, and then trigger a chain reaction with the other volcanoes creating a huge catastrophe, possibly killing hundreds of thousands of people from several nations.

With this plot in mind, Roberto, Leivinia, Mikoto, Accelerator and Touma go inside Pearl Harbor to secure the Trigger. After much trouble with Saronia A. Irivika, it was discovered that Trigger has already been utilized. In the Volcanoes National Park in the island of Hawaii, Hamazura Shiage, Kuroyoru Umidori and Misaka Worst, discover that Trigger has already been set up, and is starting activation, despite Shiage's best efforts, they are forced to retreat as Kilauea, and only Kilauea erupts.

Kilauea spews forth volcanic ash into the atmosphere spreading forth in every direction, a queer sign that Touma and company seem to overlook, as it thick lava flows should have been expected. Nevertheless, the invasion of the Hawaiian Islands begins in earnest as Trident and their occult allies from GREMLIN begin their attack on American soil.