Volcanoes

Question 1

What is a volcano?

Answer 1

Avolcanois arupture on thecrust of aplanetary mass object such as theEarth that allows hotlava,volcanic ash andgasto escape from amagma chamber below the surface.

Question 2

What is volcanoism?

Answer 2

Molten magma rises within the earth and is erupted quietly as lavas or violently as pyroclastic flows

Question 3

What is a supervolcano?

Answer 3

A volcano that erupts a lot of material (put out 1000 cubic meters of material). They do not erupt very frequently. An example is the Yellowstone Volcano.

Question 4

What is the difference between lava and pyroclastic material?

Answer 4

Lava flow - the flow of molten rock from a volcano (ex: Kilauea)

Pyroclastic flow - a fast moving cloud of hot ash, gases, and rock from a volcano(ex: Mt. St. Helens)

Question 5

Controls on Explosivity

Answer 5

1. Silica content
2. Gas Content

Magmas with high amounts of silica become more viscous and sticky, which makes it more explosive

Another factor is gas richness

Question 6

Divergent Plates + Example

Answer 6

The mantle rises and melts, producing magma. This pushes the two plates apart.

The magma erupts mainly as basaltic lava flows.

Example: Erta Ale, Ethiopia

Question 7

Subduction Zones + Example

Answer 7

The subducted oceanic plate heats up as it plunges

At a depth of 80-120, melting begins

Volcanoes are parallel to the Subduction zone

Example: Mount Fuji, Japan

Question 8

Hot Spots + Example

Answer 8

Magmas from deep within the mantle

Mantle plumes stationary relative to the drifting tectonic plates

Example: Mauna Loa, Hawaii

Question 9

What are the 5 types of Volcanoes?

Answer 9

Caldera

1. Large depression caused by removal of large quantities of magma from beneath a volcano, causing the ground to collapse.
2. Wizard Island – a volcano within a volcano

Cinder Cone - a simple volcano built from blobs of lava ejected from a single vent

1. Explosive but small in size.
2. They erupt once during an episode
3. A pile of pyroclastic debris at the angle of repose
4. Basaltic
5. Example: Capulin in New Mexico

Shield Volcano – built from countless outpouring of fluid lava flows

1. Broad, gentle sloping volcano
2. Mainly basaltic lava flow
3. Ex: Mauna Loa

Statovolcano

1. Alternating layers of lava and pyroclastics
2. Mainly andesitic in composition (60% silicon dioxide, gas rich)
3. Typical of Subduction zones
4. Example: Mt. Saint Helens

Lava Dome – mound formed when viscous lava piles up around vent

Question 10

Collapsing Mechanism of Calderas

Answer 10

A collapse is triggered by the emptying of themagma chamberbeneath the volcano, usually as the result of a large volcanic eruption.

If enough magma is ejected, the emptied chamber is unable to support the weight above it.

Question 11

Types of Activity

Answer 11

Lava Outflows: a basalt lava flow, its low silica content and high temperature means it is quite fluid but stickier than maple syrup

Pahoehoe (lol) Lava: Hawaiian term for smooth ropy lava, generally exhibits fluid like textures

Aa Lava: Blocky on the surface, and comparatively cool.

Fire Fountaining: Sometimes basaltic lava can contain lots of gas. Small explosive eruptions form fire fountains which coalesce to form a lava flow

Flood Basalts: A huge basaltic eruption which forms ava plateaus. These huge outpourings may occur over several million years and contribute to mass extinctions

Lava Domes: Lava domes erupt viscous magma. As pieces of a dome break off, they fragment and create pyroclastic flows.

Prycolastic Falls: During explosive volcanic eruptions, ash falls downwind of the volcano. Ash may be deposited over a vast area

Lahars: Indonesian word for flows of water and loose volcanic debris. Prevalent at snow-clad and ice-clad volcanoes.

Debris Avalanches: Sometimes a volcanic edifice is weakened, the entire volcano may collapse. A debris avalanche occurs, and a scalloped crater scar remains.

Question 12

Lessons Learned from the Nevado del Ruiz Volcano Case Study

Answer 12

Need only a small eruption to melt ice and generate large lahars.

The lahars may travel to tens of hundred of kilmoeters from the volcano

We need effective communication among scientists, politicians, officials and the public to warn people

Question 13

Impacts and Mitigation

Answer 13

Aircraft encounters with vocanic ash are potentially fatal, as it can cause engines to fail

Therefore, good communication among volcanologists, meteorologists and pilots is essential

Monitor Gas

Monitor Seismicity

Study Geology