The islands of Hawaii were formed by volcanoes.  The "Big Island", Hawaii,  has two very active volcanoes that are responsible for many eruptions over the last two centuries. Kilauea has many smoking vents and also lava tubes which still carry hot lava into the sea.  Earthquakes caused by moving magma within the volcano are a common occurrence on the island of Hawaii.  Kilauea puts sulfur gases and 
carbon dioxide into the atmosphere around the island.  This causes the island to be cloud covered more often than any of the other islands. Kilauea has been erupting continuously since 1983.  Moan Loa is also an active volcano.  Scientists monitor all these volcanoes to help warn people when an eruption is happening.