Vesicular Basalt from Hawaii
June 26, 2002
Like frozen froth from the top of a root beer, this up close and personal look at a volcanic rock from near the SW Rift Zone of Haleakala on Maui, Hawaii gives the observer some insight into the processes which brought this piece of a volcano to light. The small holes, or vesicles, though only a few millimeters across, are the frozen shells of carbon dioxide and water vapor gas bubbles that helped to propel the molten rock to the surface at Haleakala. Under extreme pressure deep beneath the volcanic islands, water and carbon dioxide remains dissolved in the liquid basalt. But as the magma moves towards the surface, pressure is released, allowing gas bubbles to form and expand (like opening a can of soda), further propelling the 1000+ degree C mixture of rock and gas to an explosive exit from rift or crater. Rather than a quiet river of lava flowing to the sea, the exploding gas-filled cinders cool quickly in the air, and the propelling bubbles are frozen in place, compelling evidence of their fiery heritage.