Volcanoes: Formation, Types, and Activity
Summary
TLDRProfessor Dave's geology series delves into the dynamic world of volcanoes, Earth's powerful geological features. He explains how they form due to mantle melting, often at plate boundaries, and discusses their various types, including cinder cones, composite volcanoes, and shield volcanoes. The video also covers large igneous provinces, seafloor volcanism, and kimberlite pipes. It highlights the potential dangers of volcanic activity, such as explosive eruptions and lava flows, and how volcanologists predict behavior to mitigate risks.
Takeaways
- 🌍 Earth is described as a dynamic place with continental crust plates floating on a plastic-like mantle, influenced by forces like wind, water, and gravity.
- 🌋 Volcanoes are Earth's most dynamic features, present on every continent and responsible for creating over 80% of the Earth's surface.
- 🔍 Volcanologists study volcanoes by measuring emitted gases, ground deformation, and seismic activity to predict behavior and understand processes beneath the crust.
- 🌋 Volcanoes form when the mantle melts, often at divergent plate boundaries, subduction zones, or above mantle plumes, leading to different types of volcanic arcs.
- 🔥 Volcanoes can be explosive, erupting felsic lava, or effusive, erupting mafic lava, depending on their location and the composition of the crust they are on.
- 🏔 There are six main types of volcanoes: cinder cones, composite volcanoes, shield volcanoes, large igneous provinces, seafloor volcanism, and kimberlite pipes.
- 🌀 Cinder cones are small, explosive volcanoes with high gas content, forming from the rapid cooling of ejected lava into ash and cinders.
- 🏰 Composite or stratovolcanoes are tall with steep slopes, formed by alternating layers of lava and tephra, and are prone to explosive eruptions.
- 🛡 Shield volcanoes are large with gentle slopes, formed by the eruption of runny basaltic lava, and are common in Hawaii and other areas of mantle plume activity.
- 🌊 Large igneous provinces are massive deposits of igneous rocks, often associated with mass extinctions, and are thought to be caused by mantle plumes.
- 🌌 Seafloor volcanism occurs along mid-ocean ridges and rifts, influencing ocean chemistry, while kimberlite pipes bring up ultramafic magma from deep within the Earth.
Q & A
What is the primary focus of the geology series described in the script?
-The primary focus of the geology series is to explore the dynamic features of Earth, particularly volcanoes, and how they form and behave.
How are volcanoes defined by geologists?
-Geologists define a volcano as any location where lava erupts onto the surface, either as a subaqueous eruption on the ocean floor or a sub-aerial eruption on land.
What are the two main types of lava described in the script, and how do they differ?
-The two main types of lava are pahoehoe and 'a'a. Pahoehoe is a less viscous, higher temperature lava that erupts from basaltic volcanoes, while 'a'a is a more viscous, blocky lava that tends to avalanche down the volcano.
What is the difference between explosive and effusive volcanoes?
-Explosive volcanoes erupt silica-rich felsic lava and have high amounts of dissolved gases, leading to explosive eruptions. Effusive volcanoes erupt mafic lava at higher temperatures with lesser amounts of dissolved gases, resulting in less explosive eruptions.
What are the six main types of volcanoes identified by geologists?
-The six main types of volcanoes are cinder cones, composite volcanoes, shield volcanoes, large igneous provinces, seafloor volcanism, and kimberlite pipes.
Why are shield volcanoes considered some of the largest on Earth?
-Shield volcanoes are some of the largest on Earth because they are formed by the eruption of runny basaltic lava from small vents and fissures that gradually build up to form a volcanic dome with gentle slopes.
What is a large igneous province and how is it formed?
-A large igneous province is a massive deposit of igneous rocks formed by the eruption of millions of cubic kilometers of lava in a short geological time, usually associated with mantle plume activity.
How does seafloor volcanism impact ocean chemistry?
-Seafloor volcanism impacts ocean chemistry through hydrothermal circulation along the ridge, which leaches magnesium from seawater, potentially causing different minerals to precipitate from seawater and affecting marine organisms' ability to build shells.
What are kimberlite pipes and what significance do they hold for geologists?
-Kimberlite pipes are deep-seated magma conduits that bring up ultramafic magma from deep within the mantle. They are significant for geologists because they can contain diamonds, high-pressure minerals, and xenoliths, providing samples of the lower asthenosphere.
How do volcanologists predict volcanic behavior?
-Volcanologists predict volcanic behavior by measuring emitted volcanic gases, ground deformation, and seismic activity to understand the dynamic processes beneath Earth's crust.
Outlines
🌋 Introduction to Volcanoes
Professor Dave introduces the topic of volcanoes, explaining that they are one of Earth's most dynamic features. Volcanoes are found on every continent, including Antarctica, and are responsible for creating over 80% of the Earth's surface. Volcanologists study these structures by measuring emitted gases, ground deformation, and seismic activity to predict behavior and understand the processes beneath the Earth's crust. The formation of volcanoes is linked to the melting of the mantle, which can occur due to decompression melting or the addition of water. Most active volcanism occurs at divergent plate boundaries, such as mid-ocean ridges, and at subduction zones or above mantle plumes. Volcanoes can form along volcanic arcs in subduction zones or as hot spots above mantle plumes. The paragraph also reviews the types of lava and the differences between explosive and effusive eruptions, setting the stage for a deeper exploration of various volcano types.
🔥 Types of Volcanoes and Their Formation
This paragraph delves into the six main types of volcanoes identified by geologists: cinder cones, composite volcanoes, shield volcanoes, large igneous provinces, seafloor volcanism, and kimberlite pipes. It discusses the structure and activity of volcanoes, which are essentially piles of ash and lava flows. Volcanoes made of unconsolidated material like ash are weak and prone to collapse, while those primarily of lava flows are more stable. The paragraph explains the two main types of lava: basaltic (less viscous, higher temperature) and andesitic (more viscous, blocky). It also describes the explosive nature of certain volcanoes, which eject tephra and can lead to the formation of pyroclastic flows, a deadly volcanic hazard. The paragraph provides examples of each type of volcano, including scoria cones, which are small and explosive, and composite volcanoes, which are tall with steep slopes and can have explosive eruptions. The famous Mount St. Helens is highlighted as an example of a composite volcano.
🌍 Large Igneous Provinces and Seafloor Volcanism
The paragraph discusses large igneous provinces, which are massive deposits of igneous rocks formed by the eruption of vast amounts of lava over a short geological period. These provinces, such as flood basalts or traps, are associated with mass extinctions, like the Siberian traps and the Deccan traps. The paragraph also explores the role of mantle plumes in the formation of these provinces, comparing them to lollipops with a bulbous head of hot mantle material supplied by a tail connecting to the core-mantle boundary. The discussion then shifts to seafloor volcanism, which occurs along mid-ocean ridges and rift zones, and its impact on ocean chemistry. The paragraph concludes with a mention of kimberlite pipes, which are deep-seated magma conduits that bring ultramafic magma from deep within the Earth to the surface, often containing diamonds and other high-pressure minerals. The paragraph emphasizes the importance of understanding volcanoes for their scientific, economic, and safety implications.
Mindmap
Keywords
💡Volcanoes
💡Mantle
💡Subduction Zones
💡Mantle Plumes
💡Tephra
💡Pyroclastic Flow
💡Cinder Cone
💡Shield Volcano
💡Explosive Eruptions
💡Lava
Highlights
Volcanoes are present on every continent and are responsible for creating over 80% of Earth's surface, above and below sea level.
Volcanologists predict volcanic behavior by measuring emitted volcanic gases, ground deformation, and seismic activity.
Volcanoes form at divergent plate boundaries, subduction zones, and mantle plumes, with different characteristics depending on the crust type (continental or oceanic).
Volcanoes erupt different types of lava: felsic lava tends to be explosive and found on continental crust, while mafic lava is effusive and found on oceanic crust.
There are six main types of volcanoes: cinder cones, composite volcanoes, shield volcanoes, large igneous provinces, seafloor volcanism, and kimberlite pipes.
Scoria cones, or cinder cones, are small volcanoes with high gas content that form rapidly and are short-lived.
The 1943 eruption of Parícutin in Mexico serves as an example of the rapid growth of a scoria cone, forming a 150-meter volcano in just a week.
Composite volcanoes, or stratovolcanoes, are known for their alternating layers of lava flows and tephra, with explosive eruptions due to high water content in the magma.
Pyroclastic flows, which move at speeds of up to 700 kilometers per hour and reach temperatures of up to 1,000°C, are the deadliest volcanic hazard.
The 1980 eruption of Mount St. Helens was the deadliest volcanic event in U.S. history, with a lateral explosion that devastated a large area.
Shield volcanoes are formed by runny basaltic lava, typically away from plate boundaries, with slopes less than 10 degrees and large diameters.
Large igneous provinces (LIPs) involve massive lava eruptions that occur over a short time span and are often linked to mass extinction events.
The Siberian Traps and Deccan Traps are two well-known LIPs associated with mass extinctions, including the end-Permian and end-Cretaceous events.
Kimberlite pipes are magma conduits that bring up material from deep in the mantle, including diamonds and other high-pressure minerals.
Modern volcanologists use seismometers and satellite measurements to monitor signs of volcanic eruptions, such as gas leaks, ground deformation, and increased seismic activity.
Transcripts
he knows a lot about the science star
Professor Dave explains
throughout this geology series we've
been describing the Earth as a dynamic
place where huge plates of continental
crust float Atop A plastic-like mantle
and the forces of wind water and gravity
create unique sedimentary rocks but now
we're going to explore one of Earth's
most dynamic features of all volcanoes
we've all heard of volcanoes before as
these are fascinating and Powerful
structures making them the subject of
myth and Legend over the Millennia
volcanoes are present on every continent
even Antarctica and they are responsible
for creating over 80 percent of Earth's
surface above and below sea level
geologists Define a volcano as any
location where lava erupts onto the
surface either as a subaqueous eruption
on the ocean floor or a sub-aerial
eruption on land the geologists who
study volcanoes who are called
volcanologists measure emitted volcanic
gases ground deformation and seismic
activity in order to predict volcanic
behavior and understand the dynamic
processes beneath Earth's crust we
talked about how volcanoes form when we
were learning about igneous minerals so
let's start with a quick review
volcanoes form above areas where the
mantle melts either due to decompression
melting or melting from the addition of
water most of the ACT active volcanism
on Earth occurs that divergent plate
boundaries especially mid-ocean ridges
on land volcanism occurs along
subduction zones and above mantle plumes
volcanoes form along a curved line
called a volcanic Arc at subduction
zones which corresponds to the area
where the subducted slab releases its
chemically bound water into the mantle
when the overriding plate is oceanic
crust the chain of volcanoes is called
an island arc and when the overriding
plate is continental crust it is called
a continental Arc volcanoes that form
above mantle plumes are called hot spots
which is the only type of volcano that
can form outside of plate boundaries
finally volcanoes on continental crust
tend to be explosive and erupt felsic
lava while volcanoes on oceanic crust
are effusive erupting mafic lava
having reviewed volcanisms causes let's
Now list the types of volcanoes there
are six main types that geologists have
identified on Earth
Cinder cones composite volcanoes
shield volcanoes large igneous provinces
seafloor volcanism and kimberlite pipes
before we elaborate on each type let's
talk a bit more generally about volcanic
structure and activity volcanoes are
essentially just giant piles of
inter-layered Ash and lava flows that
erupt from the volcano's vent or vents
volcanoes that are primarily made of
unconsolidated material like ash are
very weak and prone to collapse whereas
more solid volcanoes that are mainly
lava flows are more structurally sound
there are two main types of lava POI
which is a less viscous higher
temperature lava that erupts from
basaltic volcanoes and aha which is a
more viscous blocky lava that sort of
avalanches its way down the volcano
collapsing under its own weight in
addition to Lava volcanoes can erupt
solid material generally called tephra
which can range from Ash to large
volcanic bombs which are boulder-sized
pieces of material that solidify in the
air during eruption another important
property of is its explosivity explosive
volcanoes erupt silica-rich felsic lava
and have high amounts of dissolved gases
especially water and effusive volcanoes
erupt mafic lava at higher temperatures
and have lesser amounts of dissolved
gases explosive volcanoes tend to form
along Continental arcs while effusive
volcanoes are most common among
mid-ocean ridges and seamounts where
they sit on oceanic crust now back to
the types of volcanoes scoria cones
sometimes called Cinder cones are the
smallest type of volcano standing
between a dozen and one thousand feet
tall they are notorious for their High
dissolved gas content and quick growing
short-lived nature eruptions are powered
by the pressure of their dissolved gases
which come out of solution during
eruption and get frozen into the newly
formed rock this type of volcanic rock
is said to be vesicular
scoria cone eruptions are spattery and
explosive due to their high gas content
when volcanoes erupt explosively their
ejected lava rapidly cools as it flies
through the air forming tiny particles
of Ash and glassy chunks of rocks called
cinders
they are called Cinders because they
resemble ash from a coal furnace though
explosive in nature scoria cones erupt
basaltic lava the volcano itself which
is mainly made of pieces of cinders
piled up at the angle of repose is more
like a pile of sediment than a Rocky
Mountain and is therefore easily eroded
the formation of the volcano parakuten
nicely illustrates the rapid growth of
Cinder cones on February 20th 1943 a
Mexican farmer named dionisio pulido was
tending to his field when suddenly the
ground began to shake and soon swelled
two meters upward forming a fissure that
spewed sulfury Smoke by Nightfall lava
was shooting from the fissure and a 50
meter tall volcano had formed by morning
rising to 150 meters after a week
the volcano stopped erupting in 1952 but
not until forming a scoria cone 424 feet
tall and spreading lava over 26 square
miles in addition to destroying Polito's
Farm the volcano leveled the two nearest
towns and displaced thousands
composite or stratovolcanoes usually
form at subduction zones especially
Continental arcs when most people
imagine a volcano in their minds they
are probably imagining a stratovolcano
stratovolcanoes can rise as tall as 8
000 feet with steep slopes up to 36
degrees the name strata volcano arises
from its structure which is alternating
layers or strata of lava flows and
tephra with a central vent those
stratovolcanoes can produce lava flows
the lava they extrude usually just piles
up atop the vent forming a giant blob of
viscous magma called a lava Dome once
the lava Dome solidifies it plugs up the
volcano stopping it from releasing its
pressure this in combination with the
high water content of their lava leads
to a tendency for extremely explosive
eruptions strata volcano lava is viscous
for two reasons first it is about 500
Degrees lower in temperature when
compared with an effusive volcano like
Hawaii and second it is rich in silica
when silica is a component of a melt it
polymerizes or forms networks of bots
which makes it increasingly resistant to
flow with increasing silica content when
an explosive eruption occurs the pile of
lava and tephra that is the volcano can
be partially or entirely blasted away
and incorporated into a hot rapidly
moving mass of Ash Rock and gas called a
pyroclastic flow after being blasted
into the air by the eruption the
pyroclastic material begins to fall back
down to Earth where it flows along the
ground and spreads out reaching speeds
of up to 700 kilometers per hour with
temperatures of up to 1000 degrees
Celsius
pyroclastic flows are the deadliest
volcanic Hazard and obliterate anything
in their path one of the most famous
composite volcanoes is Mount St Helens
which erupted on May 18 1980 in the
deadliest volcanic event in American
history instead of blowing its top like
most volcanoes Mount St Helens exploded
from the side which directed The
pyroclastic flow laterally flattening an
area 23 miles wide by 19 miles long
large trees were snapped at the base of
their trunks like Twigs 185 miles of
Highway were destroyed and 57 people
were killed
shield volcanoes are some of the largest
volcanoes on Earth and they commonly
formed by mantle plume activity away
from plate boundaries they almost
exclusively extrude runny basaltic lava
from small Vents and fissures that
gradually build up to form a volcanic
Dome with slopes less than 10 degrees
the diameter of typical shield volcanoes
can range from three to four miles with
Heights up to two thousand feet
the Hawaiian Islands are some of the
best examples of shield volcanoes
Mount Aloha one of the Earth's most
active volcanoes is the largest spanning
74 miles from north to south and rising
over 28 000 feet above the ocean floor
large igneous provinces are massive
deposits of igneous rocks where in some
cases millions of cubic kilometers of
lava have been erupted in a very short
amount of time geologically speaking
with the bulk of the magmatism occurring
in less than one million years in most
cases
one type of lip called flood basalts or
traps are large igneous plateaus with a
step-like morphology and are associated
with many of Earth's worst mass
extinctions for example the Siberian
traps which we discussed in the tutorial
regarding Earth's history are often
cited as being the triggering event of
the end Permian mass extinction which
was the worst mass extinction of all
time
in addition another flood Basalt called
the Deccan traps began erupting around
the time of the end Cretaceous
Extinction event which is typically
attributed to an asteroid impact can
this be a coincidence or perhaps the
asteroid impact somehow triggered this
eruption this is a hotly debated topic
among geologists
lips can form over both Oceanic and
continental crust and do not correlate
with tectonic environments so what
causes them due to the extremely high
heat flow required to produce so much
magma over such a short period of time
it has recently been accepted that
mantle plumes are the culprit mantle
plumes sort of resemble lollipops and
have a bulbous head of swirling hot
mantle that is supplied by a smaller
tail which connects down to the core
mantle boundary so as the head of a
plume reaches the crust it causes a
short period of intense volcanism that
tapers off as its tail nears the surface
the Columbia River Basalt is a
well-studied flood Basalt that began
erupting around 17 million years ago in
Southeastern Oregon it is composed of
over 300 individual lava flows with
around 10 000 years between major
eruptions the onset of volcanism was
sudden and intense with 85 percent of
the lava erupting over a 1 million year
period between 15 and 16 million years
ago which slowly tapered off to widely
spaced and sporadic eruptions by 13
million years ago eruption of this lip
was probably related to the Yellowstone
hotspot which was located beneath
Southeastern Oregon during the onset of
volcanism though this too is a highly
debated topic
seafloor volcanism occurs along
mid-ocean ridges where basaltic lava
erupts from large linear volcanoes or
fissures Fisher volcanoes also occur
along areas that are rifting such as
Iceland and East Africa the vast
majority of the lava that is erupted on
Earth over its history has come from
Fisher volcanoes along mid-ocean ridges
the intensity of seafloor volcanism also
has a large impact on Ocean chemistry
due to hydrothermal circulation along
the ridge leaching magnesium from
seawater during times of Rapid sea floor
spreading so much magnesium is removed
from the ocean that different minerals
begin to precipitate from seawater which
even affects the ability of marine
organisms to build their shells
most of the material erupted from
volcanoes comes from the upper mantle
and lower crust but there are cases
where deeper material can get dragged to
the surface during an eruption Kimber
light pipes are deep-seated magma
conduits or pipes that draw up
ultramafic magma from 150 to 450
kilometers below the surface and exhibit
violent explosive eruptions that rapidly
carry mantle material to the surface
Kimber lights often contain diamonds and
other high pressure minerals like COA
site a polymorph of quartz they also
have an unusual chemistry for ultramafic
rocks being rich in potassium sodium
phosphorus and carbon in addition Kimber
lights can contain fragments of rock and
large crystals called xenoliths that
provide geologists with their only
physical samples of the lower
asthenosphere the most recent kimberlite
eruption occurred ten thousand years ago
in Tanzania
so that covers the types of volcanoes
and their formation while volcanoes are
fascinating and awe-inspiring they can
also be extremely deadly and dangerous
sulfuric gas emissions razor-sharp
tephra lung filling Ash molten lava
pyroclastic flows and fast-moving mud
flows of volcanic ash called lahars
cause widespread health effects and
property destruction however with new
developments in seismometers and
satellite measurements of ground
deformation volcanologists can monitor
the telltale signs of volcanic eruptions
some of the most important signs of a
volcanic eruption are gas leaks
deformation or bulging around the
volcano increased seismic activity and
phreatic eruptions where steam is
released from volcanic vents of course
most of us do not live near active
volcanoes but many people do and these
structures remain an important focus of
geological research
thanks for watching subscribe to my
channel for more tutorials support me on
patreon so I can keep making content and
as always feel free to email me
professordaveexplains gmail.com
[Music]
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