Hawaii is known for its striking volcanoes scattered around the islands, but many don’t know much about the variety of lava these volcanoes can produce. When the volcanic substance made of liquid and solid rock remains below ground, it is known as magma. Once magma is exposed to the air, either through a volcanic eruption or a fissure in the earth, it becomes lava. The behavior depends on its chemical composition. Low silica, which is common in Hawaii, flows and can travel for great distances. High silica, also called pyroclastics, explodes in ash or cinders when it leaves a volcano. In addition to having varying silica levels, Hawaiian lava generally comes in three forms. Check out how diverse!
Nearly all lava in Hawaii erupts as pahoehoe.Fast-flowing, it hardens into a smooth, rope-like solid because the outermost lava of a channel cools before the inside. Such a delay in solidification produces lava tubes; it can flow within these tubes for long distances.
A type of pahoehoe, pillow, lava forms when it flows into the ocean. When the it makes contact with water, a solid crust forms immediately. As more of it flows beneath the crust, the crust cracks and oozes “pillows,” or blobs.
Some attribute the name of this form to an old tale about Captain Cook walking barefoot across the lava, screaming, “Ah! Ah!” In actuality, the term means “to glow” in Hawaiian. Slow-moving aa is characterized by its rough and jagged appearance—its the reason why sturdy shoes are needed in Hawaii Volcanoes National Park. Its flows are thicker than those of the other forms and have been known to pile up (sometimes to heights of over 100 ft.). Pahoehoe can become aa if it experiences an increase in viscosity—that is, if it cools or loses gas.
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