Lecture 10 - Volcanic hazards Flashcards
When do Pahoehoe flows form?
They form when low viscosity lava cools with a ropy, smooth surface. It means “smooth, unbroken lava” in Hawaiian.
When do A’a lava flows form?.
They form when more viscous lava solidifies with a rough, jagged surface and holes through which gases have escaped. It means “stony rough lava” in Hawaiian.
What are ballistics?
Ballistics includes blocks and bombs. Lava bombs occurred in the 2018 Kīlauea eruption in Hawai’i.
What are shockwaves?
They are atmospheric pressure waves that exceed the speed of sound and can cause minor damage.
What is an example case study for the deadly effects of volcanic gases?
In 1986 a limnic eruption at Lake Nyos, Cameroon released ~200,000 tons of CO₂ that had been dissolved deep in the lake. 1,746 people and 3,500 livestock were asphyxiated. Since 1986, scientists have implemented a degassing program: a pipe in that runs to the bottom of the lake and allows the gas to escape at a regular rate, and a solar-powered alarm system monitors CO2 levels.
What is an area know to be at risk from a limnic eruption?
Lake Kivu, Rwanda is known to be at risk from limnic eruptions: its waters currently hold ~65 km³ of methane and ~250 km³ of CO₂. 2M people living within the basin are at risk of a sudden overturn.
What is an example case study for the effects of climate modulation?
In April 1815 Mount Tambora started a 4 month long eruption that would be the largest volcanic eruption in recorded history. The enormous volumes of SO₂ gas ejected by Tambora and oxidized into sulphate aerosols changed the Earth’s climate for a whole year. The eruption killed tens of thousands of people on the Indonesian islands of Sumbawa and Lombok. Earth’s mean surface temperature dropped ∼1–3 degrees ◦C for over one year, and in Europe 1816 became known as the “year without a summer”.
What were two unexpected consequences of the 1815 Mount Tambora eruption?
High food prices contributed to the invention of the bicycle in 1817.
Also in the summer of 1815 Mary Shelley wrote Frankenstein at Lake Geneva during a storm caused by the eruption.
What is a pyroclastic flow?
It is a rapid gravity current of hot pyroclastic debris and gas that travels downslope from a volcano.
What are the possible triggers for pyroclastic flows?
collapse of a volcanic dome
spillover from a crater
a direct blast from an explosive eruption
the collapse of a plume (eruption column) under its own weight
What is an example case study for the deadly effects of pyroclastic flows?
Mt. Unzen, Japan.
In 1991, collapse of a newly-formed magma dome generated a pyroclastic flow that killed 43 people.
In 2014 a phreatic eruption killed 63 people.
What are some of the effects of ash fall?
Near the volcano, the weight of ash can collapse buildings.
Inhalation of fine ash can lead to the lung disease silicosis.
Dispersal of ash in the stratosphere can disrupt air travel, as happened after the phreatic eruption of Eyjafjallajökull, Iceland in April 2010.
Why was the Eyjafjallajökull, Iceland eruption in 2010 so disruptive?
Since volcanic ash is hazardous to aircraft, airspace over NW Europe had to be shut down for eight days, stranding millions of passengers.
What are lahars?
Lahars are volcanic mudflows, formed of pyroclasts mixed with debris and water. Historically they may be the deadliest of volcanic hazards.
How can lahars form?
from pyroclastic flows that become diluted with river water or meltwater
from volcanic landslides that mix with water, snow or ice
from natural failure of a crater lake
from rainfall on loose tephra, or from condensation directly out of an eruption column
