Volcanology Flashcards
What is volcanism?
It is the process of the formation of magma that move towards the earth’s surface
What are the rock layers in the earth’s crust responsible for?
For the formation of volcanoes
What is a volcano?
It is a mountain that forms when molten rock erupts
What is magma?
It is the first stage in creating a volcano. It is melted rock deep in the crust that is subjected to high amounts of heat and pressure
What happens when lava cools?
It solidifies and creates igneous rocks
What is a magma chamber?
This is where magma is stored
Where is a magma chamber found?
In the mantle
How is magma formed?
When heat and pressure melt the rocks found in magma chambers, beneath the earth’s surface
What is a crater?
It is the opening of a volcano
What is lava?
It is the product of magma as it forms when magma reaches the surface
How does lava cause eruption?
It has a high viscosity which resists movement, causing the vents to clog, building up pressure in the volcanoes, causing eruption
What does lava turn into?
Pyroclastic materials as it hardens and is being shot into the air
What is a vent?
It is the tube-like passageway where magma passes as it reaches the surface/crater, turning into lava
What is a fissure?
It is the long cracks in the earth’s crust where lava flows
What are secondary vents?
They are side vents where magma can pass through on the side
What are the 3 parts of the earth?
Crust, mantle, and core
What is the outermost layer of the earth?
Crust
What is the crust?
It is the outermost layer in solid-state
What are the 2 types of crusts?
Continental and Oceanic Crusts
What is a continental crust?
This is where humans are situated as it carries the continents
What is an oceanic crust?
This is where sea creatures are situated as it carries the oceans
Where are tectonic plates found?
In the crust
How are continental crusts formed?
By convergent plate boundaries
How are oceanic crusts formed?
By divergent plate boundaries
What is the Pacific plate?
It is the largest plate where the Philippines is located
How is the pacific plate formed?
By transform plate boundaries
What is the reason why the Philippines is part of the Pacific Ring of Fire?
Due to the pacific plate
What is the middlemost layer of the earth?
Mantle
What is the mantle?
It is the middlemost layer in molten state wherein it is divided into 3 parts
What do the layers of the mantle signify?
The convection of heat happening in the mantle
What are the different layers of the mantle?
- Orange: hottest part (top)
- Light Orange: medium hot (middle)
- Yellow: least hottest (bottom)
Why is the yellow layer of the mantle the least hot?
Because cool air goes down
What is the asthenosphere?
It is the jelly part between the crust and mantle. Most say that it is apart of the mantle
What is the use of the asthenosphere?
It is slippery, so it helps the crust remain in solid and stable form
What is the innermost layer of the earth?
Core
What are the 2 cores?
Outer and Inner Cores
What is the outer core?
It is in a liquid state therefore the temperature is very high
What is the inner core?
It is in a solid-state despite the extremely high temperature due to the tremendous amount of pressure present
How do volcanoes form?
From the eruption of molten rocks, lava flows from vents and builds up a volcanic cone,
What happens after melting in the mantle and crust?
Volcanoes release molten rock, ash, and poisonous gas
What are the 3 major zones of volcanic activity?
Divergent and Convergent plate boundaries, and hotspots
How do divergent plate boundaries form?
When 2 plates move away from each other, creating the vent of the volcano
What occurs in divergent plate boundaries?
Convection current
How does convection current occur in divergent plate boundaries?
Hot air rises while cold air sinks, causing pressure buildup and movement, resulting to volcanic activities and finally, eruption
What kind of eruptions do divergent plate boundaries produce?
Effusive eruptions, meaning active but quiet
What type of lava do divergent plate boundaries produce?
Basaltic lava
How do convergent plate boundaries form?
The less-dense plates subduct toward the denser plates, resulting in melting. When 2 plates move toward each other, pressure and movement from melting is emitted, giving rise to volcanic formation.
How are trenches formed?
Once oceanic plate converges with continental plates
What are trenches?
Deep part of the ocean
What happens as magma interacts with water in convergent plate boundaries?
Gases accumulate and magma pressure builds up. The excessive amounts of pressure will then cause the volcano to erupt
What kind of eruptions do convergent plate boundaries produce?
Violent, meaning erupts without warning
What type of lava do convergent plate boundaries produce?
Granitic lava
What happens if both convergent continental plates subduct?
The magma will be buried deep in the crust, hence a volcano will not form
What is a hotspot?
Regions of great heat and pressure in the mantle. A tube-like area in the middle of tectonic plates where convection current occurs
Where are hotspots usually found?
Hawaiian area, also known as “The Hawaiian Hotspots” (not part of Pacific Ring of Fire)
Describe Taal Volcano?
It is a volcano within a volcano: seen on an island in Taal Lake within Luzon. It is currently an active volcano, level 1
How to classify volcano types?
By structure and by activity
What are the 3 types of volcanoes by structure?
Cinder cone, shield, and composite volcanoes
What are the features of a cinder cone volcano?
It is the most common type and the smallest. Has a large crater, narrow base, and steep sides. A smaller version of composite volcanoes
How do cinder cones form?
By small fragments of rocks piling on one another.
What are the features of a shield volcano?
It is non-explosive and is smaller than cinder cone. It has a wide base and flat top
How do shield volcanoes form?
Its lava flow is less viscous so it spreads out and travels long distances laterally
What are the features of a composite volcano?
It is the most explosive, tallest, steepest, mountain-like structure with a broad base.
How do composite volcanoes form?
Its lava flow is highly viscous so it solidifies without traveling too far laterally, hence the steep sides. After an initial explosion, lava flows from the volcano, forming alternating layers
Why are composite volcanoes highly explosive?
Due to its high viscosity, resulting in greater pressure that allows for an eruption to occur violently
What are the 3 types of volcanoes by activity?
Active, dormant, and extinct
Describe an active volcano?
Its magma chambers are full so it is greatly forseen to erupt again
Where are active volcanoes found?
Convergent and divergent boundaries, and hotspots
Describe a dormant volcano?
Its magma chambers are filling up so they are potentially active volcanoes that may erupt in the foreseeable future due to the presence of volcanic activities
What are composite volcanoes also known as?
Stratovolcanoes due to their alternating layers
What are dormant volcanoes also known as?
Sleeping or hibernating volcanoes
What are examples of volcanic activities?
Earthquakes, changes in landforms, and changes in behavior of animals
Where are dormant volcanoes found?
Convergent boundaries due to the sudden shifting of plates
Describe an extinct volcano?
Its magma chambers are out of magma supply therefore they are considered dead and inactive. The plates are no longer above the hotspots and the lava has cooled down
When does a volcanic eruption occur?
When lava and gas are ejected from a vent
What are the 2 main types of eruptions?
Effusive and explosive
What is an effusive eruption?
It is a light eruption therefore lava is less viscous and fewer amounts of gases are emitted. No pyroclastic flow is being ejected upwards
What are the 2 types of effusive eruptions?
Icelandic and Hawaiian eruptions
What is an Icelandic eruption?
Effusive, lava flowing in the landform, forming lava plateaus
What is a Hawaiian eruption?
Effusive, eruption in Hawaiian area that forms shield volcanoes
What is an explosive eruption?
It is a destructive and massive explosion wherein lava is highly viscous and large amounts of trapped gas are present.
What are the 4 types of explosive eruptions?
Strombolian, vulcanian, pelean, and plinian
What is a Strombolian eruption?
Explosive, least destructive. Small eruptions of pyroclastic flow upward
What is a Vulcanian eruption?
Explosive, bigger eruptions than strombolian of pyroclastic flow upward. Gas and volcanic ash as a product, forming dark clouds
What is a Pelean eruption?
Explosive, dense pyroclastic flow to the side rapidly
What is a Plinian eruption?
Explosive, most destructive. Very tall pyroclastic flow resulting in massive ashfall.
What are the products of volcanic eruptions?
Lava flow, lahar (mudflow), pyroclastic flow and ashfall, earthquakes, formation of igneous rocks
What is lahar?
Mud flow, ash mixed with water
What are pyroclastic materials?
Rock fragments, ashes, gases, fragments, lapili (volcanic bombs) ejected by the volcano during an eruption
Why is there ashfall?
Due to the ash going down when pyroclastic materials are ejected by the volcano
How are igneous rocks formed?
When lava cools down and hardens
What are some common igneous rocks?
Andesite, basalt, diorite, granite, and pumice
What is the best benefit of volcanic eruptions to humans?
Soil enrichment, that allows for rich vegetation, resulting to balance in the ecosystem. Pyroclastic materials ejected by a volcano are rich in nutrients and minerals that benefit plants
What elements are pyroclastic materials made of?
Fe, Mg, and N
What are other benefits of eruptions to humans?
Volcanic island formation, Minerals and stones, Global cooling, Hot springs
Describe volcanic island formation?
Benefit, materials inside the earth are pushed out the surface, creating different landforms during endogenic processes
What are endogenic processes?
Plate movements and convection of magma
Describe the presence of minerals and stones after an eruption?
Benefit, when molten rock is ejected off the surface, the area is being showered with minerals which benefits tourism and history
Describe the benefit of global cooling after an eruption?
As heat and pressure are released, balance is restored. Also, gases and ashes block out excessive UV rays
Describe the benefit of the formation of hot springs
Hot springs regulate blood pressure and produce electricity or geothermal energy
What are the ways to predict volcanic eruptions?
By geological observations, seismic activities, emission of gases, ground deformation, and biological observations
What are geological observations?
This is the act of experts observing endogenic processes and the history of volcanoes
What are seismic activities for?
Seismic activities are earthquakes and are a sign of volcanic eruptions. It happens when there is the convection of magma underneath which makes plates move due to pressure, as heat is released, causing the shaking
What are examples of ground deformation?
Landslides and rockslides
What are biological observations?
This refers to the unusual behavior of animals as they have good instincts to sense bad occurrences
Name and describe the alert levels in the Philippines?
0: no alert
1: no eruption is imminent although low-level unrest is felt
2: increasing unrest
3: increasing tendency toward eruption
4: intense unrest, an eruption is possible in a few days
5: hazardous eruption imminent
What is the crust also known as?
Lithosphere
How many tectonic plates are there in the crust?
15-20 plates
Where are shield volcanoes found?
Along hotspots
Where are composite volcanoes found?
Along the pacific ring of fire and subduction zones
