WEEK 13 - Volcanoes Flashcards
Where do most volcanoes occur?
Most volcanoes occur along plate boundaries.
Exceptions are hotspot volcanoes, which form within plates due to stationary mantle plumes.
What is the behaviour of volcanoes with mafic magmas?
Mafic magmas have low viscosity (are “runny”) due to low silica content (~50%).
Low volatile content.
Produce volcanoes that erupt relatively gently.
Typically associated with hotspot volcanoes and divergent plate boundaries.
What is the behaviour of volcanoes with intermediate to felsic magmas?
High viscosity (“stiff and gooey”) due to high silica content (~60–70%).
High volatile content.
Erupt explosively.
Typically found at convergent plate boundaries.
What is a caldera and how does it form?
Formed during extremely violent eruptions.
Summit of the volcano collapses inward.
Massive release of pyroclastic debris and gases through ring fractures.
Collapse creates a large crater called a caldera.
How did Crater Lake, Oregon form?
Formed ~7,000 years ago from eruption of Mt. Mazama
Created a caldera ~10 km wide
Eruption deposited a thick ash layer over large parts of western U.S. and Canada
One of the best-known calderas today
How do volcanoes affect the atmosphere and climate?
Explosive eruptions release gases + fine debris into the atmosphere
These particles reflect solar radiation, reducing incoming sunlight
Can cause global cooling and climate changes
EXAMPLES: Krakatau (1883), Mount Tambora (1815), Toba (73,500 B.C.E.)
What happened during the Toba eruption (73,500 B.C.)?
One of the largest volcanic eruptions known
Created a caldera 100 km wide
Ash layer 15 cm thick found over 1000 km away
Ejected ~2800 km³ of ash (solid rock equivalent)
Ash reached 30 km into the atmosphere
How did the Toba eruption impact global climate and humans?
Ash & aerosols may have caused tropical freezing for days/weeks
Cool temperatures could’ve lasted up to a decade
Likely led to massive environmental stress
Possibly pushed humans close to extinction
What were the global effects of the 1815 Tambora eruption?
Sulphur dioxide → sulphate aerosols → reflected sunlight
100 km³ of ash ejected
Blocked 10% of sunlight
Caused global temperature drop (up to 5°C)
Led to severe weather worldwide
What was the “Year Without a Summer” and what caused it?
Year: 1816
Caused by: Tambora eruption (1815)
Ash and aerosols blocked sunlight
Result: Cold weather, crop failure, starvation
What unusual weather happened in 1816 due to the Tambora eruption?
Snow in New England during summer
Cold and dark summer across Europe
Nicknamed: “Eighteen Hundred and Froze to Death”
How did the Tambora eruption influence the writing of Frankenstein?
Old weather forced Mary Shelley and friends to stay indoors
In Switzerland, group wrote ghost stories
Mary Shelley created Frankenstein
How is volcanism connected to The Scream by Edvard Munch?
Sky in The Scream possibly inspired by volcanic sunsets
Volcanic aerosols may have affected colors and mood of the painting
What emotions are shown in Edvard Munch’s The Scream?
Themes: confusion, despair, anxiety
Partly influenced by his sister Sophie’s mental illness
How many versions of The Scream did Edvard Munch make?
Created 4 paintings and 1 lithograph
Norwegian title: Skrik (means “The Scream”)
Most famous version made in 1895
When was the first version of The Scream painted?
Painted in 1893
Part of a series called “The Frieze of Life”
Used oil, tempera, and pastel on cardboard
What inspired The Scream and related paintings?
Inspired by Munch’s early bohemian life (1883–1884, in Oslo)
Munch had already made sketches and written texts for the ideas by 1885–1889
He described the paintings as illustrations of memoirs from 1884
Munch felt melancholy and anxiety while walking with friends
Described the sky as “blood red” with clouds like fire
He felt a “great, unending scream” in nature
What happened to the 1893 version of The Scream?
Stolen from the National Gallery in Oslo in 1994
Held for ransom, but recovered by police
What happened during the eruption of Krakatau in 1883?
Krakatau exploded on August 27, 1883
Island obliterated by the explosion
Tsunamis traveled thousands of kilometers
40,000+ people killed
Sound heard 3,000 miles away
What global effects did the 1883 Krakatau eruption have?
Shock waves recorded 7 times around the planet
Ash and dust circled the globe
Block of coral blown onto Java by explosion
How did the 1883 eruption of Krakatau affect sunsets?
Sunlight reflected off particles from the eruption, reddening sunsets
Crimson skies reported farther north as ash and dust spread
Similar effect noted after the 1991 eruption of Mt. Pinatubo
What did space observations reveal about volcanic eruptions and sunsets?
Sunset view from the space shuttle Endeavour
Volcanic dust visible over a year after the Mt. Pinatubo eruption
How did other artists respond to the Krakatau eruption?
William Ascroft created 500+ watercolors of the Krakatau skies
Alfred Tennyson wrote about it in the poem “St. Telemachus” (1892)
What happened during the 2018 eruption of Anak Krakatau?
Anak Krakatau (“Child of Krakatau”) formed in 1927 from the caldera left by the 1883 eruption
2018 eruption caused the collapse of the southwest portion of the volcano
The eruption triggered a tsunami affecting Java and Sumatra
