Lecture 12 - Glaciers and Volcanic Activity

Flashcards about the interaction between volcanoes and ice.

What are some implications of sudden heat release from volcanic eruptions for glacial systems?

Ice deformation and subglacial hydrology changes

What factors primarily control acceleration, deceleration, and crevassing in glacial systems?

Topography

What controls whether meltwater is focused or distributed in a normal glacial system?

Pathways cut into bedrock or melted upwards into the ice

Where are ice-covered volcanoes typically located?

High latitudes and high elevations

What is the equilibrium line in the context of ice-covered volcanoes?

The boundary where ice accumulation equals ablation

Name regions where ice-covered volcanoes can be found.

Antarctica, the Andes, the Cascades, Alaska, Kamchatka, Japan, New Zealand, and Iceland

What different forms can ice cover take on volcanoes?

Seasonal snow, small glaciers, substantial valley glaciers, or continuous ice sheets

What is a caldera?

A depression roughly 10-12 kilometers across containing up to 500 meters thickness of ice.

How can a high geothermal flux affect glaciers?

It can elevate the glacial base temperature, causing localized melting.

Besides geothermal flux, how else can volcanic activity affect ice and snow?

Lava flows or pyroclastic density currents can disrupt or thin ice and snow

In general, how many volcanoes are active on any given day?

About 30 to 40

What event in Colombia in 1985 is an example of the worst volcano-ice interaction?

The eruption of Nevado del Ruiz, resulting in 23,000 deaths.

What were the consequences of the 2010 eruption of Eyjafjallajökull in Iceland?

Closure of European airspace due to a long-lived ash cloud causing substantial economic losses.

How is the shape of an ice cave formed by geothermal heat flux?

Dome-like

What happens to water volume when ice melts?

It decreases

What factors influence whether meltwater will escape from beneath a glacier?

High pressure or intersection with existing drainage pathways

What are Nye Channels and Rothlesberger Channels?

Interconnected pathways of cavities in the bedrock or ice that efficiently drain water.

How does low pressure in a cavity beneath a glacier affect the ice surface above it?

It pulls the ice surface down

How does ice behave at the surface of a glacier compared to the base?

It tends to fracture near the surface but flow at the base due to higher confining pressure.

What is an ice cauldron?

An area on the ice surface that has been pulled down by low pressure.

What is the long-term effect of low water pressure in a subglacial cavity?

It becomes a potential well, attracting water to equalize the pressure.

What are the Skafdao Ice Cauldrons?

Spectacular examples of ice cauldrons on top of a high geothermal heat zone that drain into the River Skafdao in Iceland.

What makes the subglacial lake in the Skafdao Ice Cauldrons warmer than typical meltwater?

Geothermal heat

What are jokulhaups?

Sudden drainage events from subglacial lakes which can cause floods.

Other than geothermal vents, what else, when introduced, can cause a high heat flux at the base of a glacier?

Magma

What causes explosions during subglacial eruptions?

Rapid heat transfer from magma to ice, causing flash heating and steam formation.

In what scenario can lava gently cool rather than explode?

High water pressure suppresses steam formation.

What is unique about the ice involved in the Eyjafjallajökull eruption?

Normally, crevasses may be twenty, thirty meters depth. Right here, those crevasses, you're talking about 100 meters or more. Those are ice cliffs. They're huge.

What is a sandor plane?

Braided river system made up of magma fragments carried by floodwater

How long did it take the 1996 Gelp eruption to melt through to the ice surface?

About two days or thirty-six hours

What do the bull's-eye features in images of the Gelp eruption show?

Depressions in the ice surface, or cauldrons, generated above the zone of melting

How deep was the ice cauldron measured during the Gelp eruption?

150 meters

What is unique about the meltwater near volcanic glaciers?

Because it can be 20 degrees celsius, it results in faster melting.

How did the hydrology of the 1996 Gelp eruption impact the eruption itself?

Efficient meltwater drainage contributed to a more explosive effect on the southern part of the fissure.

What insights did studies of GELP provide about heat flux?

Provided insights about hydrology and the mechanisms of volcanic eruption.

How much bigger was the 1918 Katla eruption compared to the GELP eruption?

Order of magnitude bigger

How did the ice covered volcano Katla act like an incubator for microbes?

Ice covered volcano provided conditions where the microbes could thrive via the methane.

What is a tinder?

Ridge of lava and ash fragments that was formed after a volcanic eruption.

How is the ice thickness of volcanoes measured?

Proxies are used, such as measuring where it was constrained and where the magma was freely flowing.

How does volcanism play a part in a snowball Earth?

Potentially, volcanic eruptions can cause ash to cover earth's ice; this would lower the albedo and help escape a "snowball trap."