3. Pyroclastic materials
• Wind will carry
small particles a
long way.
• The fragments
ejected during
eruption range in
size from very fine
dust and ash to
pieces that weigh
several tons.
4. volcano
• Anatomy of a volcano
–Activity often begins
when a fissure or crack
develops in the crust.
–A mountain formed of
lava and/or pryoclastic
material.
5. Shield volcanoes
• Are produced by the
accumulation of fluid
basaltic lava and
have quiet eruptions
• Shape of broad
slightly domed
• Most have grown
from the deep of the
ocean including the
Hawaiian Islands and
Iceland.
6. Cinder cones
• Ejects lava which
hardens in the air and
falls back down to form
the volcano.
• Produce gas rich
basaltic magma
• Short life span: Lasts
only a couple of weeks
to a couple of years and
then it never erupts
again.
7. Composite cones
• A combination of
Shield and Cinder
cone volcanoes
• Pyroclastic flows can
move down the
volcano at speeds up
to 100 mph.
• Lahars are mudflows
caused by melted
mountain ice and
snow mixed with lava
and mud.
8. Calderas
• A large depression
in a volcano caused
by the collapse of
the top of a volcano
after eruption.
• Many lakes form in
these depressions.
10. Lava plateaus
• Greatest volume of lava is excreted
from fissures
• Columbia plateau was formed this
way
• Numerous fissures erupted to form
this large landform.
11. Key Concept
• What determines the type of volcanic
eruption?
–The primary factors that determine
whether a volcano erupts violently or
quietly include magma composition,
magma temperature, and the amount of
dissolved gases in the magma.
12. Key Concept
• What other landforms are
associated with volcanic
eruptions?
–Neck, pipes, and calderas.
