Hazards BK 3 - Volcanic Hazards Flashcards
which plate margins do volcanoes occur?
Constructive
destructive continental/oceanic and oceanic/oceanic
hotspots
what determines how hazardous and how explosive volcano eruption will be
Nature of the magma
When is magma formed?
When rocks in the crust or mantle melt
How is magma classified?
according to its silicon and oxygen content (silica)
what are the three types of magma?
Basaltic, andesitic and rhyolitic
what does viscosity mean?
How runny or thick lava is
When does magma turn into lava?
When magma beneath the ground erupts onto the surface
What are some key features of basaltic magma?
45% Silica content
1000 C Eruption temperature
Very Runny
Tectonic Setting=Hotspots and Constructive margins
Not hazerdous
what are some key features of andesitic magma?
55% Silica
800 C Eruption Temperature
Sticky
Tectonic Setting = Both destructive plate margins
Very Hazardous
what are some key features of rhyolitic magma?
65% Silica Content
700 C Eruption Temperature
Very Sticky
Hotspots and Cont/Cont margins
Very Hazardous but rare
The more acidic, the magma
The more explosive the eruption
What does effusive mean?
The opposite of explosive
What are the six types of volcano?
fissure volcano, shield volcano, Dome volcano, ash- cinder volcano, composite volcano and caldera volcano
what are some features of fissure volcanoes?
they occur on cracked or faults. They are non-explosive and have a basaltic magma.
What are some features of shield volcanoes?
they are the largest, they have broad and gentle slopes. They are formed from lava that has cooled and solidified theyre non-explosive.
what are dome volcanoes made from and what are eruptions like
they are made of rapidly, cooling, viscous lava, eruptions are explosive
What are cinder volcanoes made up from
They are mounds made from basaltic magma, built up during an eruption
What are some features of composite volcanoes?
they are cone chipped and made of alternating layers of ash and lava from previous eruptions, eruptions are explosive
what are some features of caldera volcanoes?
Huge circular depressions caused by a sudden collapse of a volcano crater. During an eruption they can be formed from other volcanoes.
What is the equivalent to the Richter scale for volcanoes?
Volcanic explosivity index
what are VEI eruptions on a scale 0
quiet and effusive
what are VEI eruptions on a scale 1-3
more violent and may cause some localised damage
what are VEI eruptions on a scale 4-5
moderately explosive and damage may be on a regional scale
what are VEI eruptions more than 6
a very large scale and may cause global impacts through climate
what does the term Icelandic mean?
A term to describe, magma flow and gently through a fissure or a crack
What are Hawaiian eruptions?
Where magma flows gently from a volcano central vent
what are Strombolian eruptions?
Violent and are associated with andesitic magma
What are Pelean eruptions?
Associated with andesitic magma and include pyroclastic flows
Violent explosions
Usually clear a blocked vent
What are features of plinian/vesuvian eruptions
Violent and andesitic in nature, causing large amount of material to be ejected
What are krakatoen eruptions like
exceptionally violent in Mira move much of the volcanoes original cone
Do a effusive or explosive eruptions happen more regularly
effusive
what is the VEI of a Hawaiian, Strombolian, Volcanion, and Plinian eruptions like?
Hawaiian= 0-1
Strombolian = 3-4
Volcanian(Pelean)= 5-6
Plinian=8+
what sort of eruptions happen at shield volcanoes?
Hawaiian
What sort of volcanoes, see Strombolian eruptions?
Fissure and Cindercone volcanoes
what sort of volcano see Plinian and Vulcanian eruptions?
Composite
what sort of volcano see Krakatoan eruption is?
Caldera
where do basaltic eruptions happen?
Hotspots and constructive plates
What’s another name for Pelean eruptions
Volcanian
Where is an example of andesitic eruption volcano
The Andes or mount Pinatubo
What’s an example of where rhyolitic eruptions happen
Mount Saint Helens
what is a lava flow
Floors of magma that has been extruded from a volcano vent
is there a lava flow a primary or secondary Hazard?
Primary
what is tephra?
Solid material ejected from the eruption of a volcano, sometimes from pyroclastic fallout
what does Tephra include
volcanic bombs, lapilli and ash
what are some effects of ash?
Can cause buildings to collapse, can suffocate crops and clog river channels
is tephra a primary or secondary Hazard
Primary
What is a pyroclastic flow?
Dense fluidised clouds of ash, larger, volcanic, debris and hot gas that can travel vast distances at high speeds, destroying everything in their path
is a pyroclastic flow, a primary or secondary hazard
Primary
what is a volcanic gas
Carbon dioxide carbon monoxide, sulphur dioxide and chlorine that are all toxic
what are some impact of volcanic gases?
People and livestock to suffocate and impact in aquatic ecosystems
what are lahars?
When volcanic ash combines with water, for example, rain or a typhoon
is a lahar a primary or secondary Hazard?
Secondary
What are some impact of acid rain?
causing damage to vegetation and corroding buildings
how can volcanic eruptions impact climate change?
Debris ejected during an explosion can reach the troposphere and reduce temperatures by deflecting incoming solar radiation back to space
what are some impact of volcanic eruptions?
Homelessness, disease, disruption to flights, secondary mass movement, lack of basic necessities, transport blocked
What is a social impact of pyroclastic flows?
they cause serious, burning
