Volcanic
Landforms
CH 6 Prentice Hall
p.193-197
Shield Volcano
• A wide, gently sloping mountain.
– Lava pours out in thin layers and harden on top
of older layers.
– Viscosity= Low
Cinder Cone
• A steep, cone-shaped hill or mountiain.
– If lava is thick and stiff it may produce ash,
cinders and bombs.
– Paricutin in Mexico (farmers field 400m high)
– Viscosity = High
Composite Volcano
• A tall, cone-shaped volcano which alternates
eruptions of lava flows with explosive
eruptions of ash, cinder and bombs.
• Viscosity= High/Low
• Examples:
– Mt. St Helens
– Mt. Fuji in Japan
Lava Plateau
• Eruptions form high, level
areas by flowing from several
long cracks in an area.
• Thin runny lava travels far
before cooling and solidifying.
• The flooding process repeats
again and again building up
high plateaus over millions of
years.
– Columbia Plateau
(Washington, Oregon, &
Idaho)
Caldera
• A huge hole formed from an enormous
eruption that empties the main vent and
magma chamber beneath the volcano.
• The hollow mountain then collapses inward
due to lack of support.
• Fills with pieces of the volcano, ash and lava.
– Crater Lake in Oregon
Soils from Lava & Ash
• Ash releases potassium, phosphorus and
other materials that plants need.
• Soil develops and plants are able to grow.
• The richest and most fertile soils.
Volcanic Neck
• Forms from when magma hardens in a
volcano’s pipe.
– The softer rock wears away, exposing the hard
rock. (weathering and erosion)
Sill
• Magma that squeezes and hardens between
layers of rock.
– (Horizontal like a window sill B in the diagram)
Dike
• Magma that forces itself across rock layers
and hardens.
– (Vertical, cuts through rock layers C in the
diagram)
Batholith
• Large rock masses form that form the core of
many mountain ranges.
• Formed when a large body of magma cools
inside the crust.
– D in the diagram
Dome Mountain
• Formed by smaller
bodies of magma, when
rising magma is blocked
by horizontal layers of
rock.
– Forces rock layers to
bend upward into a
dome shape.
– Rock layers above
eventually erodes and
leave the core exposed.