Archive for April 6th, 2011

When Volcanoes Erupt

April 6th, 2011

WOOSTER, OH – Students in the Geology of Natural Hazards course spent a day studying the products of volcanic eruptions. Here are some of the outstanding samples in our volcanic collection:

Reticulite is a delicate network of basaltic glass that forms during Hawaiian fire fountaining. Volatiles expand easily in the low-viscosity magma, creating a dense network of interconnected vesicles separated by thin strands of quenched lava (sideromelane).

Accretionary lapilli are rounded pea-sized pieces of tephra that consist of volcanic ash. Ash aggregates into balls because of electrostatic forces in the eruption column.

Volcanic bombs are formed when lava is ejected and becomes airborne. The fusiform bomb has a rounded aerodynamic shape with an elongated tail, which tells us that the material was molten when it was ejected and was shaped as it traveled through the air.

The glassy surface of this basalt shows the classic ropy texture of pahoehoe. Ropy pahoehoe develops when the surface of a lava flow becomes partially solidified and wrinkles as the underlying lava continues to flow.