hyaloclastite

Volcanic vortices

We have already shared several photos from the Nature’s Best Photography, Windland Smith Rice International Awards 2013, currently on show at the Smithsonian Institution, and the winner in the Power of Nature category was one of my favourite volcano snappers.

The photo shows where the lava from the ongoing eruption of Kilauea on the main island of Hawaii meets the Pacific Ocean in an explosion of steam and burning gobbets of molten rock as fire and water meet in their endless powerful encounters. As the flow entered the sea the water started to boil, producing these amazing vortices of steam shooting up above the surface, testifying to the mixing of energies below. Usually only one or two appear, so the seven in this photo represent a rare and amazing moment in geological history, though all future geologists will have to go on to understand it will be a mound of shattered glassy lava fragments, probably altered, and known as hyaloclastite. 

Loz

Image credit: Bruce Omori/ Extreme Exposure Fine Art Gallery 

Via http://www.hawaiipictureoftheday.com/volcanic-vortices-big-island-power-of-nature

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My attractive friend here is posing next to a boninite intrusion within a hyaloclastite. Hyalolastite is a lava which forms when molten basaltic rock erupts in shallow water and boninite is a rare form of lava which is formed from a very hot and very hydrated mantle source which usually occurs during the initiation of a subduction zone.

The glassy rind around the boninite intrusion (closer detail in the lower photographs: in situ and a sample in my collection) looks like a cooled margin. In reality it’s where the intruding boninite has released all the water dissolved in the melt which has lowered the melting point of the surrounding hyaloclastite, producing the glass margin.

Lava Deltas

Just as there are river deltas, there are also lava deltas. They form when magma enters the sea and builds a wide, fan-shaped area of new land along the coastline.

When lava enters the ocean, it cools rapidly and can shatter into fragments called hyaloclastite – volcanic glass breccia ranging in size from a few millimeters to a few centimeters. The hyaloclastite becomes the loose rubble foundation that will eventually support additional layers of lava as the delta builds above sea level. These deltas may become a permanent part of the coastline, but on steep submarine slopes, the layers of hyaloclastite are unstable often leading to the sudden collapse of the deltas into the water. Collapses are a common occurrence around the active shield volcanoes in Hawaii, and there have occasionally been injuries or fatalities when people have been on a lava delta that suddenly fell into the Pacific Ocean.

Deltas being supplied with new lava – such as those around Hawaii’s erupting volcanoes, are active deltas; while those cut off from their lava supply are inactive. The pictured lava delta on Alaska’s Carlisle Island’s west coast is an inactive delta.

- RE

Photo Credit: Christina Neal, USGS, 2014

References:
http://on.doi.gov/1Pc3tnJ
http://bit.ly/1bq8tHg
http://on.doi.gov/1Hrnqo5