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.

3 Responses to “When Volcanoes Erupt”

  1. Mark Wilsonon 06 Apr 2011 at 10:15 pm

    I recognize that beautiful bomb!

  2. Matt Owenson 07 Apr 2011 at 8:59 am

    I still have some olivine-cored bombs sitting in our garden at home; collected in SE Arizona while at field camp with Becky Mellinger (89) through U of A. My kids still don’t understand why daddy gets so excited about them.

  3. Stephanie Jarvison 07 Apr 2011 at 7:51 pm

    Explaining bombs to the kiddos at Science Day last weekend was really fun–they (and their parents!) thought they were so cool :)

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