In the mantle, convection currents can
break apart, and cause a crack in the
Earth’s surface, allowing the magma to
flow up from the mantle, which hardens
on the surface, and builds up.
The older plate sinks beneath the other
plates and sinks into the mantle and makes
a deep-ocean trench. Water in the sinking
plate eventually leaves the crust and rises
into the wedge of the mantle above it. The
melting point of the mantle in the wedge is
lowered. The mantle partially melts and the
magma that forms as a result, and can
break through the ocean's crust, creating
All volcanoes have a system of
passageways, through which the
During an eruption, as the magma rises,
the pressure of the rock on the magma
When the volcano erupts, the force of
expanding gases pushes magma from
the chamber through the pipe until it
flows or explodes out of the vent.
Hot, low-silica lava which is thin, runny,
and flows easily.
Pahoehoe forms fast-moving hot lava
that is thin and runny.
Aa forms cooler, thicker, and slow-
High-silica lava is thick and sticky.
An explosive eruption will powerfully
throw the lava into the air, causing it to
break into fragments, which cool rapidly.
The smallest pieces are called volcanic
ash. The pebble-sized pieces are called
cinders. The larger pieces are called
bombs, and they can range from golf
ball sized to the size of a car.
They both cause damage from their
A quiet eruption can cover a large area of
land with a thick layer of lava.
The eruption of a volcano can last as long
as a decade to more than a million years.
Geologist classify a volcano either dormant,
active, or extinct to describe it’s stage of
If the volcano drifts away from it’s hot spot,
it may become extinct
When a volcano erupts it can make landforms out of lava, ash,
and other materials.
These landforms include shield volcanoes, cinder cone
volcanoes, composite volcanoes, and lava plateaus. Other
landforms include calderas, which are the huge holes left by the
collapse of volcanoes.
Large eruptions can empty the main vent and magma chamber
beneath a volcano. At some spots on Earth's surface, thin layers
of lava pour out of a vent and harden on top of previous layers.
Lava can flow out of several cracks in an area. Low-silica lava
can travel for miles before cooling. After millions of years, lava
floods can build up high level layers. This is called a lava plateau.
Over time, forces such as flowing water, wind, or ice can strip
away layers of the crust and expose the hardened magma.
Features formed by magma include volcanic necks, dikes, and
sills as well as dome mountains and batholiths.
A dome mountain forms when uplift pushes
a large body of hardened magma toward
the surface. The hardened forces the layers
of rock to bend upward into a dome
shape. Eventually, the rock above the
dome mountain wears away, leaving it
Batholiths are the core of many mountain
ranges. Over millions of years, the rock is
worn away, allowing the batholith to curve
upward. Flowing water and grinding ice
curve the batholith into the mountains.
How does a volcano form on a divergent
When a crack in the mantle forms, magma is
forced out of it, and after build up it becomes a
What kind of lava is sticky and thick?
What kind of landforms do volcanoes form?
Batholiths, other volcanoes, lava plateaus, dome
mountains, and calderas.
What is one of the fragments lava gets split up
Volcanic ash, cinders, or bombs.