Woods Hole Oceanographic Institution

One if by Land

Over the past two days, most of the science party participated in a field trip to look at the deposits from explosive eruptions of sub-aerial (on land) volcanoes in the Taupo Volcanic Zone (TVZ) in New Zealand. This volcanic zone is home to the super-volcano, Taupo.

The field trip was organized by James White and Rebecca Carey with help from Arran Murch. Incredibly intense eruptions from volcanoes in the TVZ over the last 26,000 years have produced huge eruption plumes up to 35 km (more than 20 miles) in height and blanketed the landscape with volcanic ash and pumice, a porous volcanic rock.

The intensity of these eruptions is a result of the rapid acceleration of magma from deep beneath Earth’s surface as water and carbon dioxide exsolve from the melt and produce bubbles that rapidly expand into the surrounding magma. Portions of the magma very quickly become buoyant and accelerate toward the surface. As the magma reaches the surface, it fragments into gas and solid, producing a volcanic particle mixture.

In the TVZ, this process was often compounded by interaction between the gas/magma mixture and water in Lake Taupo or the nearby groundwater. When this water flashed into steam, the added energy rapidly boosted the explosivity of the eruption.

On our field trip to the TVZ, we looked at deposits of pumice and ash; flows of pumice, ash, and rock; and in some cases floating pumice that resulted from the eruption interacting with paleo Lake Taupo. In quarries and at road cuts, we found deposits that retain many of the key characteristics that inform us about the conditions that produced the eruptions. We also found deposits that have been modified or reworked by transport through rivers and streams.

The initial goal of the field trip was to become familiar with sub-aerial volcanic deposits and the ways they can be reworked on land in order to think about what we might see in coming weeks. In that respect, it was a resounding success, and our curiosity is now well stoked to start our expedition to Havre submarine volcano and the remnants of the 2012 eruption on the seafloor.