|At what plate boundaries are cinder cone volcanoes
|Question Date: 2017-11-07|
Cinder cones form from volcanic pipes which
spit out hot ash and cinders. For cinders to
form, the cone has to spit out the gas-filled lava
which solidifies quickly.
But divergent plate boundaries like the
mid-Atlantic rise are usually underwater.
Cinder cones can form under the sea, but water
cools them quicker than air, and currents can
sweep ash away. Because they're so different I'm
not sure how many other scientists would call
those types of cones "cinder cones." So,
underwater cinder cones don't have it easy at
divergent plate boundaries.
Most cinder cones form from a type of lava
called basalt which can form in just about any
tectonic setting. We find cinder cones at a
convergent plate boundaries like Chile and cones
at divergent boundaries like the East African
Rift. In Death Valley, part of a transform
plate boundary, a fault has sliced at least one
cinder cone in half.
When two continents meet, like in the
Himalayas, we generally don't see as many
volcanoes at the surface; I don't know of any
cinder cones in continent-continent convergent
But cinder cones don't even need to form near
plate boundaries! Hawaii has cinder cones and
scientists suggested that some volcanoes on Mars
might be cinder cones.
Cinder cones may form along diverging plate
boundaries, near or behind the volcanic front
along converging plate boundaries and ALSO at
intra plate (no plate boundary) locations called
hotspots such as Hawaii. Cinder cones are not
associated with any one type of petrotectonic
location. In order to form a cinder cone
the magma must be saturated in H2O
or CO2 to form bubbles of gas within
the liquid part of the magma.
Cinder cones can form at a variety of plate
boundaries and even at intra-plate volcanoes
(volcanoes away from plate boundaries).
Strato-volcanoes most often form at
convergent plate boundaries (subduction zones) and
smaller cinder cones frequently form on their
There is no plate boundary near Hawaii, and the
volcanism is generated by a hot mantle
plume. However, shield volcanoes like Mauna
Kea on Hawaii, also have cinder cones on their
flanks which form during the late stages of
volcanism after the main shield stage.
The only plate boundary type where cinder
cinder cones are not common is divergent plate
boundaries (like mid-ocean ridges).
Cinder cone volcanoes form when a volcanic vent
- where lava and rock debris erupt through an
opening in the ground - erupts and sends lava
and rocky debris into the air. The lava cools and
falls down as chunks along with the rocky debris,
stacking up into a cone around the volcanic vent.
These chunks of debris are known as pyroclastic
fragments. The formation of a cinder cone is
also helped by lava flowing under the pyroclastic
fragments already accumulated around the vent,
spreading the fragments out into the
characteristic cone shape of a cinder cone.
Cinder cone volcanoes can form in a few
different tectonic settings. Many of them form
at convergent plate boundaries, where oceanic
crust slips underneath continental crust or other
oceanic crust. We call this slip
"subduction", and at these boundaries the
oceanic crust gets pulled down into the mantle. As
it moves into the mantle, it brings ocean water
with it.When ocean water and hot mantle rock
mix, the rock melts to form a magma. That magma
rises up to the Earth's surface and erupts in a
volcano! Because there's so much water in the
magma, it causes a very "gassy" explosion,
which is what forms the cinders.
Cinder cones can also form inside tectonic
plates though, where there is no boundary in
sight. These volcanoes form on top of something we
call a "hotspot", which is where really hot
rock from deep inside the earth rises up. When
that hot rock gets close to the earth's surface,
it melts to form a magma and erupts. An example of
this is Hawaii. In Hawaii, most of the volcanoes
are shield volcanoes, but there are a lot of
cinder cone volcanoes that form along the flank of
the shield volcanoes.
Cinder cones form along convergent plate
boundaries, divergent plate boundaries, and some
types of transform plate boundaries (specifically,
those that involve divergence). Basically,
anything that gets magma near the surface will
create cinder cones, whether through spreading or
The cinder cones in Oregon and Washington
that form in-between the large stratovolcanoes
that make up the Cascades are on a convergent
plate boundary. The cinder cones in Nevada
occur because the transform plate boundary at
the San Andreas Fault is actually slightly
divergent, and Nevada is being stretched
because of it.
Volcanoes can form at either convergent (two
plates colliding) or divergent (two plates going
away from each other) plate boundaries.
Different volcano types form depending on the kind
of lava that erupts -- if the lava is sticky it
usually forms stratovolcanos and if it is runny it
forms shield volcanoes. Cinder cones can
form at both convergent and divergent plate
boundaries and they are pile-ups of ejected
material from the volcano.
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