Sub-Plinian Eruptions

Photograph of Redoubt's ash cloud, taken on the morning of Thursday, March 26, 2009. Lake Clark National Park & Preserve, Alaska.

Photo by Robert Cole, Peninsula Airways pilot.

Introduction

Sub-Plinian eruptions produce higher eruption columns than Vulcanian eruptions, but are not as explosive as Plinian eruptions. Sub-Plinian eruption columns are usually less than 12 miles (20km) in height, and are unsteady but sustained.

All types of Plinian eruptions (Sub-Plinian, Plinian and Ultraplinian) are caused by gas exsolution in volatile-rich silicic magmas. Because of these magmas’ high viscosity, vesiculation shatters. The expanding bubbles and pyroclasts are erupted together in high speed jets that thrust eruptions into the stratosphere.

Composite volcanoes experience Sub-Plinian eruptions. Sub-Plinian eruptions may also be associated with volcanic domes.

Ash, fallout deposits of highly vesicular pyroclasts and pumice, pyroclastic flows, and lahars are produced in Sub-Plinian eruptions.

Mount Rainier experienced a Sub-Plinian eruption 2,200 years ago that produced the C-tephra which is found near the Sunrise Visitor Center. Redoubt Volcano in Lake Clark National Park and Preserve experienced several Sub-Plinian episodes during its 1989-1990 eruption.

Rarely, some large cinder cones can experience Sub-Plinian eruptions. The 1085 CE Sub-Plinian eruption of Sunset Crater Volcano is the most explosive eruption of a cinder cone that has been documented. It is estimated that the eruption column reached 65,000 feet, and tephra deposits from the eruption covered an area of almost 200 square miles (500 square km). This extremely explosive cinder cone eruption was propelled by unusually high concentrations of CO2 in the magma.

• Typical magma composition: silicic (dacitic)

• Description: Catastrophic, cataclysmic

• Eruption Products: tephra, pumice, fallout tuff, pyroclastic flows, lahars

• National Park examples: Mount Rainier, Redoubt Volcano in Lake Clark National Park and Preserve, Sunset Crater Volcano National Monument

Related Links

• NPS Volcanoes—Eruption Classifications

• Aniakchak National Monument & Preserve (ANIA), Alaska—[ANIA Geodiversity Atlas] [ANIA Park Home] [ANIA npshistory.com]

• USGS Alaska Volcano Observatory—Aniakchak Peak

• Lake Clark National Park and Preserve (LACL), Alaska—[LACL Geodiversity Atlas] [LACL Park Home] [Volcanoes of Lake Clark] [LACL npshistory.com]

• USGS Alaska Volcano Observatory—Redoubt (located in Lake Clark)

• Mount Rainier National Park (MORA), Washington—[MORA Geodiversity Atlas] [MORA Park Home] [MORA Volcanoes] [MORA npshistory.com]

• USGS Cascades Volcano Observatory—Mount Rainier

• Sunset Crater Volcano National Monument (SUCR), Arizona—[SUCR Geodiversity Atlas] [SUCR Park Home] [SUCR Geology] [SUCR npshistory.com]

• USGS Yellowstone Volcano Observatory—San Francisco Volcanic Field (includes Sunset Crater)

Volcanoes, Craters, and Lava Flows