EAPS 106 Exam 2

The connection between the Tambora eruption and monsters

during the cold, dreary summer of 1816 by the 1815 Tambora eruption (VEI 7), while vacationing together in Switzerland, Mary Shelley came up with Frankenstein and John Polidori came up with the Vampyre.

How tsunami and windblown waves differ

Windblown waves only move water at the surface, while tsunamis are started at the based of the water column (carry a much larger volume of water, longer wavelength, and travel further inland), can be the same height as tsunami waves, tsunami waves volume are much much larger than windblown, which makes them more dangerous

Which combinations of magma viscosity and gas content lead to effusive and explosive eruptions

effusive: low gas content (0.5/2%), low viscosity, hotter eruption temperature, low SiO2 content (~55% by mass). Explosive: high gas content (4.0/6.0%), high viscosity, cooler eruption temperature, high SiO2 content (~70% by mass).

Why pressure builds in magma as it rises near the surface

dissolved gases in the magma expand to form gas bubbles as the pressure decreases (due to moving closer to the surface). But as the gas bubbles take up more volume, pressure in the magma increases (even as it moves closer to the surface).

What giant flood basalts are and where they originate from

giant flood basalts are relatively large volcanic flow that occur over relatively short time periods, it forms when mantle plume heads first reach the surface then melt due to depressurized melting.

About how many volcano related deaths have occurred in the past 500 years

more than 250,000 people have been killed by volcanic hazards in the past 500 years.

The four main types of eruptions and their relative explosiveness

(1) Hawaiian Eruption: < 2km / 6500 ft (height of eruption column), very fluid lavas, low gas content, low viscosity, calmest of four, (2) Strombolian Eruption: <10 km / 38800 ft, driven by the bursting of large gas bubble, (3) Vulcanian Eruption: < 20km / 65600 ft, large enough to generate shock waves, (4) Plinian Eruption: <55 km / 180400 ft, largest and most violent, sending columns of pulverized rock and ash 10s of miles up into the atmosphere, can get both ash and lava, through rare.

How the DART tsunami early warning system works

Deep Ocean Assessment and Reporting of Tsunamis Early Warning System: a water pressure detector sits on the ocean floor, measurement are sent by acoustic signal to a buoy on the surface and the buoy send the signal further to a satellite and the signal is then sent to early warning stations inland, can send out tsunami warnings in a little as 15 minutes after an earthquake including path and size measurements.

How the Hawaiian Islands generate tsunamis

Hawaii is the world's largest mountain and is continually growing, as it grows pieces fall off the sides and cause underwater landslides which shift water and create tsunamis.

The tallest mountain on Earth measured from its base to its top

Hawaii, Mauna Kea (shield volcano, mostly underwater).

What is noteworthy about Iceland's volcanoes

Iceland is a hotspot that overlies a mid ocean ridge the only place above sea level where a mid ocean ridge and hotspot overlie, over the past 500 years, Iceland's volcanoes make up 1/3 of the total global lava output.

What processes will cause already hot, but not yet melted rocks, to melt

Increase temperature: while this could work to melt rocks, there are few processes in the crust that will cause rocks to heat up, so this is not a common way to induce volcanism, decrease pressure: (aka depressurized melting), this reduces the melting temperature of rocks, which experience a decrease in pressure if they rise closer to the surface thus enabling already hot rocks to melt (common at mid ocean ridges and hotspots), add water to the mineralogy: (aka hydration induced melting), this breaks up long silica chains, which reduces the rock's melting temperature and thus can cause already hot rocks to melt, occurs at subduction zones.

Why inlets are particularly dangerous places during a tsunami

Inlets (natural harbor) are particularly dangerous places because the incoming water becomes trapped and piles up since it has nowhere to go (usually due to high mountains/elevation that surround the area)

The kind of volcano that Mount Vesuvius is

Mount Vesuvius is stratovolcano.

How Pompeii was preserved for 2000 years

The ash from the eruption solidified around the bodies and building overtime.

The process by which subduction zone earthquakes cause tsunamis

The most common means of generating a tsunami is uplift of the seafloor from elastic rebound during a large subduction zone earthquake.

Whether strikeslip earthquakes can cause tsunamis

They cannot: will not cause a change in the height of the seafloor, do not displace any water (no tsunami), exception: can cause underwater landslides.

How the current size of the magma chamber under Yellowstone is measured

Yellowstone's seismic network and robust seismicity can be used to reveal characteristics of the magma chamber beneath (seismic imaging), Yellowstone's current magma chamber has been imaged by measuring the change in speed of seismic waves as they pass under the park.

The reasons why so many people died around the Indian ocean due to the 2004 tsunami

a lack of theses three things are reasons why so many people died and how it could have been prevented, education about tsunamis, an early warning system to detect tsunamis, a system to notify the public if a tsunami is suspected.

How much of the United States was covered by ash from Yellowstone supereruptions

a little under half of the US (cutoff at around the Midwest).

What harmonic tremors are

a small earthquake in terms of shaking that lasts a very long time (many minutes). It happens when magma moves underground.

Where hot spot tracks are found

all over the world, hot spot tracks on the same plate move in similar manner, showing the plate motion.

How long it takes a tsunami wave to cross the Pacific Ocean

almost a day.

The factors that influence how much gas pressure can build up below the surface of a volcano

amount of magma: the more magma, the more dissolved gas, amount of dissolved gas: the more gas the greater potential for pressure build up, viscosity of magma: low viscosity magmas will flow through cracks in the surface (effusive), while sticky magma will resist flow and allow great pressure to build up (explosive).

The evidence that indicates past large explosive volcanic eruptions at Yellowstone

ash was found as far away as Kansas, after a farmer was digging a bit there was almost a 1 m thick layer of ash 50% of the United States was covered in ash, we know this because Yellowstone has three calderas with large associated pyroclastic flows.

Which process has the potential to cause the largest tsunamis

asteroid impacts, through most common, earthquakes generally cause the smallest tsunami waves, volcanic eruptions and landslides can also create pretty big tsunamis.

What a lahar (mudflow) is

avalanches of ash, soil, rock, and water that can occur days or even months after an eruption.

Where hot spot plumes begin to melt

base of the lithosphere.

The kind of volcano low viscosity magma will lead to

broad, shallow sloped shield volcanoes, vs. high viscosity magma, narrower and steeply sloped stratovolcanoes.

The characteristics of a tsunami waves in deep water compared to shallow water

deep water: long wavelengths, low wave heights, and great speed / shallow water: reduced wavelength, increased height, slower speed

What causes hot rocks to melt at hot spots

depressurized melting.

Who Pliny the Younger was

described the eruption of Mt. Vesuvius and the destruction of Pompeii and Herculaneum, Plinian eruption are named after Pliny the Younger (full name, Gaius Plinius Caecilius Secundus).

Why geysers erupt but hot springs do not

hot springs are continuously replenished due to straight plumbing, geysers erupt periodically due to the bends in the plumbing, both are fueled by hot water reservoirs heated by an enormous reservoir of magma beneath them.

The consequences of a supereruption at Yellowstone today

hundreds of people would die due to pyroclastic flows, thousands of people would die due to ash fallout, millions of people would die due to global cooling.

What causes hot rocks to melt at subduction zones

hydration inducted melting: water pushed out from the subducting plate lowers the melting temperature of the hot mantle above, causing it to melt, pressure is pushing water out.

What it might mean if you feel shaking near the shore in terms of tsunami potential

if the shaking is significant, there was likely a subduction zone earthquake several hundred kilometers out, then you have about 20 to 40 minutes before tsunami hits, so head to higher ground.

What caused the largest tsunami runup in the past 100 years

in 1958 a tsunami generated by an avalanche into Litya Bay, Alaska (2000 ft rockfall scrap).

That Yellowstone has also experienced large lava flows

in addition to large explosive eruptions, Yellowstone has also had a series of large lava flows demonstrating the variability of volcanic eruptions.

The kind of volcanic process that created Mount Vesuvius

it was formed by a subduction zone along the coast of Italy; magma was generated beneath it from hydration induced melting.

Which volcanic hazard cause the most and least fatalities near a volcano

lava is the least dangerous, pyroclastic flows are the most dangerous.

What an effusive volcanic eruption is

lava just "calmly" spills out and flows.

Where hot spot plumes originate from

made of hot (but solid) mantle from the core-mantle boundary.

How calderas form

magma chamber collapses in on itself after an eruption.

The difference between magma and lava

magma is below earth's surface, lava is found above earth's surface (both are melted, but the name is changed based on its position relative to the surface).

The tectonic settings where the different types of volcanism are found

mid ocean ridges, subduction zones, hot spots, only hot spots are often found far from plate boundaries.

How stratovolcanoes form

midsize volcanoes that form due to alternating layers of pyroclastic flows and effusive lava flows.

That the mantle is not a subsurface ocean of magma because its temperature is less than its melting temperature

most of the mantle is below its melting point (magma is not formed), magma only exists in very specific places in the mantle, and makes up a small percentage of the mantle.

The relative difference in size of eruptions at different VEI levels

multiply by 10 at each level, i.e. VEI 2 is .001 km3 , VEI 3 is .01km3 etc.

How the bodies of the Pompeii dead were recovered after 2000 years

pouring plaster into the cavities left by the decaying bodies in the solidified ash to create molds of the bodies.

The characteristics of volcanic pumice

pumice is a volcanic rock with so many trapped gas bubbles that it floats, very lightweight.

What viscosity is a measure of

resistance to flow in fluids/how easily a fluid flows, ex: water has low viscosity, molasses has high viscosity.

About how many people have been killed by tsunamis in the past 1000 years.

several hundred thousand.

The characteristics of volcanic ash

shards of volcanic glass leftover from magma gas bubbles, smaller than sand grains, hard abrasive corrosive electrical conducting does not dissolve in water, not fluffy like ash from wood or barbeque, 15 cm of west ash can collapse a roof, 5 cm will kill crops, 1 mm will close an airport, very good fertilizer once it is incorporated into the soil.

What volcanic ash is

shards of volcanic glass, melt sand to create glass, it's conductive, small rocks, microns in size.

The likely effects of a 10 km diameter asteroid hitting the Gulf of Mexico today

significant amounts of death, sinking a majority of the south the coast of Mexico

That volcanic flows can sometimes be stopped by spraying water on them or redirecting them

spraying water only works sometimes: water spray stopped the lava flow from moving down a street in Iceland in 1973, attempts were made to save the National Park Service in Wahaula Visitor Center in 1989 by spraying water on the lava flow. The center was destroyed.

What the Ring of Fire refers to

subduction zone volcanism around the plate boundaries of the Pacific Ocean, all subduction zone volcanoes from inboard of the trench above where the subducting plate reaches ~ 100km depth.

Whether the San Andreas Fault has the ability to cause a large tsunami

the San Andreas Fault is a strike slip fault and therefore cannot create a tsunami.

Why the Toba eruption was an important event in human history

the Toba supereruption (VEI 8) in Sumatra 74,000 years ago led to global cooling that almost wiped out humanity: Toba caused a 6 to 10 year cooling of 3 to 5 degrees C which may have triggered the onset of a 1000 year long ice age, this ice age reduced the human population to under 10000 mating pair (maybe as few as 1000).

Why the destruction of Pompeii in 79 AD is so remarkable

the ash preserved the forms of the dead, 16,000 people were killed, a description of the eruption was written down by the Pliny the Younger.

Why giant flood basalts may have caused extinction events

the dinosaurs may have gone extinct 65 million years ago when an steroid impact triggered the Deccan Traps giant flood basalt, large amounts of greenhouse gases led to global warming and acid rain.

What a pyroclastic flow is

the heavier parts of an explosive eruption that run down the flank of a volcano at up to 200 mph. Powered by expanding hot gasses at over 1000 degrees C.

Why hot spot volcanism leads to a chain of volcanoes

the hot spot stays stationary, but as the tectonic plates move, a line of volcanoes will form, Hawaii is an example of this, most of Hawaii's volcanoes are dormant since they're no longer over the active hot spot.

That pyroclastic flows can sometimes be directed away from populated areas

the people that live beneath Mount Unzen, Japan have built channels that can direct pyroclastic flows away from residential areas.

What the Volcano Explosivity Index (VEI) scale is a measure of

the relative explosiveness of volcanoes, based on the volume of ash and rock ejected.

Why being a good swimmer is probably not going to save you from a tsunami

the tsunami picks up loose debris, meaning you are more likely to get crushed before drowning.

What caused the tsunami that killed 36,000 people in Indonesia in 1883

the volcanic eruption of Krakatoa.

Why there are fewer volcanoes in the southwest US compared to the northwest

there are no active subduction zone in the southwestern US, so there are fewer active volcanoes compared to the northwestern US, Juan de Fuca Plate is disappearing into the North American Plate in the northwestern US.

What a volcano cannot look like before an explosive eruption

there cannot be lava exposed at the surface, since you can't build pressure in that case.

How many large explosive eruptions have occurred at Yellowstone in the last 2.1 million years

there have been 3 extremely large explosive eruptions, two of which were supereruptions: we know this because Yellowstone has three calderas with large associated pyroclastic flows (also because of ash we've found), based on the calderas, there have been 3 really big explosions at Yellowstone (not necessarily eruptions).

Why Yellowstone is considered a hidden supervolcano

there's no obvious volcano, but there have been 3 major explosive eruptions there in the last 2 million years, with 2 being supereruptions.

The global consequences of large explosive volcanic eruptions

these massive explosive eruptions emit large amounts of SO2 which reacts with oxygen and water vapor to create sulfuric acid droplets, the ash and sulfuric acid droplets block sunlight and cause global cooling, greatly reducing the global temperature due to how long they can remain in the atmosphere: the sulfuric acid droplets stay aloft longer than the ash and can be more detrimental to climate.

How we know about past tsunamis in Japan and along the Washington/Oregon coast

tsunami stones in japan are placed along the farthest place past tsunamis hit, along the pacific northwestern coast, sand deposits show the history of tsunamis in the area.

Why it is dangerous to return to the shore after a tsunami wave

tsunami waves are not just a single wave, usually 3 to 10 waves over a span of several hours, often the second or third wave is largest.

The most likely cause of a tsunami in the Atlantic Ocean

underwater landslides on the flanks of volcanoes like the Canary Islands, which have steep underwater cliff faces.

How we monitor pressure changes in a magma chamber

uplift of the ground at Yellowstone, as measured by GPS, is related to pressure within the magma chamber: many small earthquakes occurring in a short amount of time indicated the movement and release of volcanic gas, which results in a drop of pressure and ground elevation.

How volcanic gases lead to lakes of acid

volcanoes can create lakes dense with sulfuric acid (from mixing sulfur, oxygen, and water), but this process takes many years to build up a strong acid content.

What a tsunami seawall is

walls built along the shoreline to keep tsunami waters from reaching inland, however Japan's seawalls were 4/6 meters high; it was not prepared for the 10+ meter waves.

How we know Yellowstone is a hot spot

we know that Yellowstone is a hotspot because it lies at the end of a trail of extinct volcanoes and the trail of volcanic flows that lead up to it.

How a cinder cone forms

when tephra (air cooled lava fragments) are thrown out of a volcanic vent underneath.

When water waves will typically break

when the depth of the water is equal to the wave height (does not happen in deep water), one giant tsunami has multiple breakpoints *water moves out first for a few minutes and then reverses to come onto the shore.

Why the sea level sometimes drops before a tsunami arrives

when the tide goes out very fast and very far (over the span of 10/20 minutes), you have 5/10 minutes to get to higher group before a tsunami hits, trough created by the subduction zone pulls the water out and then the water crests and comes in.

What a boat in the middle of the ocean will experience if a tsunami wave passes beneath

would rise less than a meter over a period of 10s of minutes and thus not even know that a tsunami has passed underneath because the wave height in water is not very tall until it begins to hit the shore.

Whether Japan should have anticipated the wave heights of the 2011 tsunami

yes they have 3 10+ meter high tsunamis in the past 400 years.

Whether volcanic eruptions can be predicted

yes, explosive volcanic eruptions are generally preceded by several precursors associated with a build up of pressure beneath the surface that enables eruptions to sometimes be predicted to within a few days.