is hot melted rock found when a volcano is erupting. It comes from
deep inside the earth where there is a lot of heat. Lava can reach
temperatures from seven to ten times as hot as boiling water. There
are many types of ways for lava to flow. Two common types of lava
flows are called by Hawaiian names, "Pahoehoe" and "aa"
because they come from volcanoes in Hawaii. Pahoehoe has a smooth
rolling surface. Aa lava has a very rough surface. Both Pahoehoe
and Aa lava are mostly made of basalt. There is a type of lava called
basalt which is a dark
grey or black color.
made from andesite makes
smooth-sided blocks of lava. Blocks are formed by andesite because
it is less viscous than basalt. That means that it is thicker and
cools off slower than basalt. The thick andesite lava flows slowly.
Strato volcanoes usually erupt lava made of andesite. Lava domes
are made of andesite lava.
and ryolite lava flows are the slowest flowing lava. They are very
thick and viscous. These kinds of lava erupt from strato volcanoes
and can be very explosive. Large amounts of gas gets trapped in
the thick lava and cause very violent eruptions. When the ryolite
lava cools it forms a black glassy lava field.
Most lava is made up of basalt. Basalt lava has less gas in it
than lava made up of other substances like andesite or rhyolite.
Basalt lava is thinner than other kinds of lava, so it flows faster
than most other kinds of lava. Gases from inside the volcano can
rise to the surface of basalt lava easily. That means that huge
amounts of gas do not collect and cause severe eruptions. These
kinds of eruptions with basalt lava means that the eruption is not
too severe, but there is a lot of lava that flows out of the volcano's
The thin basalt lava has a low viscocity rate. That means that
it is runny and thin. Other kinds of lava have higher viscocity
rates. That means that they are thicker and could have big pockets
of gas. The more gas that is trapped in lava means that the eruption
will be more violent.
A volcano's effusive rate is determined by the kind of lava and
how much flows out of the volcano during an eruption.
is called magma or molten
rock before it comes out of an active volcano. Lava makes many different
kinds of formations as it flows and begins to dry.