SIO 45 Final - UCSD

volcano

A vent or fissure in the Earth's surface through which magma and gases are expelled

volcanology

the study of volcanoes and volcano-related phenomena

Eruption

an event where magma emanates from the earth's surface

Magma vs. Lava

Magma is composed of molten rock and is stored in the Earth's crust. Lava is magma that reaches the surface of our planet through a volcano vent.

why do we study volcanos?

○ Hazards (and how to avoid them)

○ Saves lives, prevent property damage

■ Ex. Geologic hazards

○ Energy (volcanoes give off heat)

■ Ex. Geothermal heat

○ To understand the Earth and climate

○ To find and use raw materials (minerals, etc.)

○ Agriculture (volcanic soils are fertile)

○ Because they are beautiful and awe-inspiring

why do volcanos erupt? (volatiles)

Volatiles make eruptions possible; volatiles in magmas de-gas (pressure drops)

and the resulting pressure drives an eruption

■ Volatiles are dissolved gases in magma

■ Most common ones are H2O, SO2, and CO2

■ Exsolution = de-gas

why do volcanos erupt? (Magma)

Magma viscosity and gas content determine explosivity

■ Viscosity = resistance to flow

■ High viscosity + volatiles = Explosion

● High viscosity = higher amounts of silica = sticky

■Low viscosity + volatiles = lava flows

● Low viscosity = lower amounts of silica = liquid

shield volcano

● A broad, domed volcano with gently sloping sides, characteristic of the

eruption of fluid, basaltic lava

○ Typically passive

● Passive eruptions and lava flows out; solidifies and adds layers

● Polygenetic: multiple eruptive episodes

Cinder/scoria cone

Scoria (cinder) cone are simplest volcanoes, built from particles and blobs of congealed lava ejected from single vent. The lava blown out fall as cinders around the vent to form cone (hence the name)

Composite Stratovolcano

a large, cone-shaped subaerial volcano consisting of alternating layers of lava and tephra

Explosive, cone-shaped, violent ● In between explosive episodes there are lava flows ● Fragmentation, ash, mud flows

Hawaiian:

passive, continuous gas streaming, can be energetic due to higher gas release

Plinian

most viscous, explosive, convecting column of gas, rock, and ash

Continuous, sustained eruption

Explosive, convecting column of gas, rock, and ash (up to 55 km)

Strombolian:

rhythmic bursts of gas without a sustained eruption, consequence of gas bubble bursting in the vent

Vulcanian:

Non-continuous bursts (short, intermittent blasts) at intervals (min-hours)."Throat-clearing eruption" (up to 20 km)

Peleean:

Associated with lava domes, a collapse or small explosion results in pyroclastic flows. Can be hot or cold

Surtseyan

Pulsating eruption of steam a

Lava flows

Pahoehoe: Smooth and ropy

A'a: Rough and jagged

Both are basaltic lava flows

Fountains

Higher gas pressure drives a fountain of lava high into the air. Sometimes as high as 2000 feet!

Fissure Eruptions

Lava emanates along a fissure (crack) in the ground. Fissures can be formed by tectonics or erosion.

Tubes, Tunnels, Spatter, Skylights

Lava tubes form when surface flows crust over and flow beneath the surface.

When holes develop in the roof of a tube system, it is called a skylight.

Lava Lakes

Surface bodies of molten lava.

Usually are contained within depression such as a crater or vent in a volcano.

Few active in the world (< 10).

What is tephra?

rock fragments and particles ejected by a volcanic eruption.

ash

pyroclastic particles less than 2 mm in diameter that erupt from a volcano

Lapilli

pyroclastic particles between 2 mm and 64 mm in diameter that erupt from a volcano

Bombs (ballistic projectiles)

pyroclastic particles larger than 64 mm in diameter that erupt from a volcano

What are pyroclastic density currents (PDC)?

clouds of ash, gas, fragmentation form from a collapse of an explosive eruption

How is a pyroclastic flow different from a surge?

Pyroclastic flows are high-density currents of pumice, ash, blocks, and volcanic gas that rapidly move down the slopes of a volcano.

Pyroclastic surges are low-density currents of ash, pumice, crystals, and volcanic gases that are more dilute than pyroclastic flows

What is a Plinian column and why do pyroclastic flows result from them? How do they form?

Plinian eruptions are marked by columns of gas and volcanic ash extending high into the stratosphere, the second layer of Earth's atmosphere.

The longer eruptions begin with production of clouds of volcanic ash, sometimes with pyroclastic flows.

Columns fall and result in pyroclastic flows due to the aggregation of ash

Lahars (Volcanic Mudflows)

Formed by the sudden mixing of large volumes of pyroclasts with water (e.g. heavy rain, draining of crater lake, melting of glacier)

supervolcanic eruption

Large-scale, violent (plinian-ultraplinian) eruptions that frequently result in a caldera. Supervolcanoes are different from a normal eruption in terms of the amount of ash they produce in which can be in the range of 100s-1000s km of ash.

caldera

a large crater caused by the violent explosion of a volcano that collapses into a depression

How do calderas form?

Calderas form when the summit of a volcano collapses.

example of a caldera

Yellowstone

where do most volcanos occur?

Most volcanic activity occurs at convergent boundaries

ash fall

The deposition of a layer of fine airborne rock and glass that have been erupted from a volcano

Ash flows (& surges)

Ash can clog airplane engines, abrade surfaces, and penetrate the cabin

Gases

Gases emitted replace oxygen, which can kill people, animals, and vegetation

What parts of the U.S. have the highest volcanic risk? What parts have the lowest?

○ Highest risk: west coast

○ Lowest risk: east coast

volcano monitoring: field observations

● Where did past eruptions go?

● What types of deposits erupted?

● Were the eruptions passive or explosive?

volcano monitoring: Seismology (earthquakes)

constant monitoring of earthquake activity

earthquakes can be precursors to volcanic eruptions

also can occur during an eruption

volcano monitoring: Deformation (includes remote sensing techniques (satellite, InSAR, etc.)

■ Depressions or inflations can determine magma location and depth

■ Can estimate volume and pressure change

■ Techniques:

● Precise leveling

● Tilt

-> Tiltmeters (Change in distance and elevation when reservoir swells)

-> GPS

■ Small movements in the crust can be calculated

● Laser ranging (EDM)

○ Electronic Distance Measurement

● InSAR (radar interferometry)

○ Satellite images are recorded and compared

volcano monitoring: Gases

■ Samples are taken from vents near/on a volcano using Giggenbach flask

■ Samples can be taken from the air surrounding the volcano - COSPEC

how each category is used to understand a volcano's behavior

○ Geology: creates a timeline of eruptions; may show patterns of behavior which we can use to predict a future eruption

○ Seismology: earthquakes may be a sign that a volcano is about to erupt since volcanic activity and earthquakes are associated with plate tectonics

○ Deformation: bulges can indicate an increase in pressure and volume

○ Gases: changes in volcanic/magmatic gases may indicate an increase in activity

super volcano

○ It has a VEI of 8+; 100-1000 km3 of volcanic material is erupted

○ Large-scale violent (plinian - ultraplinian) eruptions that result in calderas

risk

Hazard x Value x Vulnerability / Capacity

What are some of the strategies used to reduce volcanic risk?

Identify hazard areas

Monitor volcanoes

Develop an emergency plan

Explain how volcanic eruptions affect climate change.

Volcano's throw out large amounts of sulfur dioxide, water vapor, dust, and ash which influence climatic patterns for years through increasing reflectivity causing atmospheric cooling. Tiny particles called aerosols are produced by volcanoes. They reflect solar energy back into space and have a cooling effect on the world.

How did volcanoes play a roll in past extinction and climate change?

Prior to the land extinction of dinosaurs, volcanoes appear to have caused a massive ocean extinction of life forms. This happened because of extensive volcano eruption in place like India, lasting for 100,000 years. Scientists studying fossils from Seymour island have identified a thick bed of sediment. The amount of layers prove there was two extinctions that killed of species of snails and clams living on the ocean floor. This evidence proves green house build up from volcanoes, leading to a warming environment in the ocean and resulting in species extinction.

Mt. St. Helens

○ Stratovolcano

○ The Juan de Fuca plate (oceanic) subducts under the NA plate (continental)

○ 1980 eruption

■ Magma intrusion generates tremors until it creates a bulge

■ An earthquake triggers the collapse of the northern flank causing a lateral blast

● Landslide was a product; pressure on magma was released

■ A full vertical eruption eventually occurs

● Plinian column carries ash into the air

types of volcanic products emanated from MSH

○ Ash/tephra ○ Landslide ○ Mudflows ○ Pyroclastic flows

What has been happening to MSH since the 1980 eruption?

○ Increased seismic activity

○ Difference in elevation due to erosion & crater rock collapses

how are the Hawaiian Islands are forming

hot spot

mantle plume and how it creates volcanic islands like Hawaii

Areas where heat/and or rocks in the mantle are rising to the surface - a hot spot is the surface expression of a mantle plume

What are the 2 active volcanoes on the big island of Hawaii?

Kilauea and Mauna Loa

When did the recent, continuous eruption of Kilauea begin?

1983

What types of volcanic features can be found on Hawaii?

○ Lava flows: Pahoehoe & A'a ○ Lava "fire hoses" ○ Lava tubes: lava moves underground in system of tubes/tunnels; empty out leaving a void/tunnel ○ Rifts: fissure eruptions ○ Lava lake ○ Scoria cones

What is a pit-crater? How is it different from a true caldera?

○ Like a caldera, but no eruption from crater

○ Collapse from the void from an empty magma chamber

Know the very basic sequence of events that occur during an eruption at Hawaii (ex. inflation, etc. etc.)

○ At Kilauea

■ Rapid inflation

■ Harmonic tremors and short period earthquakes

■ Changes in concentrations of gases: Sulfur dioxide, carbon dioxide, etc

■ Changes in magnetic, gravity, geo-electric fields and intensities

■ Eruption

What are rifts? Why is the eruption at Hawaii occurring along these rifts?

○ Magma is convecting

○ Flex & deflate ■ Crust breaks and cracks

○ Open pathways that magma can travel

What happens when lava and H2O interact?

Hydrovolcanic eruption

What kind of volcano is Mt. Vesuvius?

Stratovolcano

What happened during the 79 A.D. eruption of Vesuvius?

○ Pyroclastic flows and ash fall killed the people of Pompeii and Herculaneum ○ Large plinian column

What is a plinian column? Who is it named after?

Plinian eruptions, also known as Vesuvian eruptions, are volcanic eruptions marked by their similarity to the eruption of Mount Vesuvius in AD 79.

Pliny the Elder took his fleet across Naples Bay totry to rescue inhabitants near the volcano (hedied as a result)The convecting, eruptive column was namedPlinian after Pliny the Younger's description

What is the threat today around Mt. Vesuvius? Why do we care about Vesuvius at all?

The infamous volcano is best known for its nearly instantaneous decimation of neighboring towns Pompeii and Herculaneum in A.D. 79. Considered one of the world's most dangerous, it is also the only active volcano on Europe's mainland. Nevertheless, 600,000 people live in the 18 towns at its base that comprise the "red zone."

Campi Flegrei

The Phlegraean Fields is a large region of supervolcanic calderas situated to the west of Naples, Italy.

Yellow stone

supervolcanogiant volcanic systemmagma chamber under Yellowstone and a hot spot

Yellow stone-ramifications of a large eruption?

SO MUCH ASH

difficult for society

large earthquakes

no access to food water, no travel, no medicine

not a good situation

disruption locally and globally

>Will block out solar radiation

>Result in freezing temperatures

>Crops will not grow

>The economy will collapse

>It is believed society would not survive

Yellow stone-are most yellow stone eruptions explosive?-whats most likely to happen?

in our life time no, smaller eruption of steam, viscous, lava flows

SMALL hydrothermal eruptions likely

Large Earthquakes and Landslides

Yellow stone-whats least likely to happen?

explosive eruptions

caldera forming eruption

How did the Mt. Pinatubo (1991) eruption affect the people of the Philippines?

800+ fatalities

5,000 evacuated

destruction from lahars and ash

lahars continued for years due to rain mixing with ash

clark air base- evacuated yet heavily damaged

philippines revoked lease- US left clark airbase and subic bay lower global temp

What role did the USGS VDAP team play in forecasting the eruption?

○ Flew in months in advance after observing signs of a possible eruption

○ Worked extensively with the Philippines' gov't

○ Set up an observatory

○ Drew up evacuation zones on existing hazards

○ 5000 lives were saved

○ $250 million in damages saved

Mt. Pinatubo-What role did Typhoon Yunya play?

typhoon hit Philippines as Pinatubo erupted

rainfall caused significant lahars as rain mixed with ash

ash redistributed all over island of Luzon

Iceland-Why is volcanism occurring here?

big hot spot seated on mid ocean ridge

-Atlantic ridge

-divergent

Iceland-What are the tectonic settings?

big hot spot

mid ocean ridge

divergent boundary

Iceland-Implications of major eruption?

beautiful sunset (atmosphere affect)

climate change (cooling)

agriculture (starvation, famine)

no air travel (ash)

breaks down societal service that are necessary

Iceland-How does ash affect global climate?

large silica volcanic eruption

puts ton of ash in atmosphere

blocks sunlight (ultra violet)cleared out of atmosphere relatively quick

short lived in comparison to gasses affect

Iceland-how does aerosols(gases) affect global climate?

○ More gas = more climate change ■ Can take effect over decades ○ Sulfur rich gases ■ Blocks sunlight and creates sulfuric acid H2SO3

What happened as a result of the 1783 eruption of Laki in Iceland? How did it become responsible for the largest number of volcano-related fatalities in recorded history?

passive fissure eruption of lava in Iceland over 14 months

major famine in Iceland and northern europe-25% died

6 million deaths worldwide

poured out illuminated amounts of lava

fluid lava flow and eminent aerosols in atmosphere

starvation is number one volcano killer

What has happened in 2021 in Iceland? What has the eruption been doing (style? Type of eruptive products?

After more than a year of unrest, a small effusive eruption commenced in Fagradalsfjall, Iceland, on 19 March 2021. The eruption lasted six months. The first six weeks were characterized by multiple fissure openings, and the remainder was dominated by effusive activity from a single crater.