Volcanic Landforms - Guide For Reading (Page 2 of 4) in pdf

Volcanic Landforms - Guide For Reading Page 2

Some volcanic landforms are formed when lava flows build up

mountains and plateaus on Earth’s surface. Volcanic eruptions

create landforms made of lava, ash, and other materials.

Landforms formed when lava flows build up:

1. shield volcanoes- At some places on Earth’s surface, thin layers

of lava pour out of a vent in a quiet eruption. More layers of such

lava harden on top of previous layers. The layers gradually build a

wide, gently sloping mountain called a shield volcano. Broad &

flat like a shield. Ex. Hawaiian Islands

2. composite volcanoes- Sometimes lava flows alternate with

explosive eruptions of ash, cinders, and bombs. The alternating

layers from quiet and explosive eruptions form a tall,

cone-shaped mountain called a composite volcano.

Ex. Mt. Fuji, Mt. St. Helens

3. cinder cone volcanoes- If a volcano’s lava has high viscosity,

the lava may explode into the air and harden into ash, cinders, and

bombs. These materials pile up around the vent, forming a steep,

cone-shaped hill or mountain called a cinder cone.

Ex. Paricutin, Mexico; Sunset Crater, Az

4. lava plateaus- Some eruptions of thin, runny lava flow out of

cracks and travel a long distance before cooling and hardening

forming high level areas. Over millions of years, these layers of

lava build up over a large area to form a lava plateau.

Ex. Columbia Plateau

An enormous eruption may empty a volcano’s main vent and

magma chamber. With nothing to support it, the top of the

mountain collapses inward. The huge hole left by the collapse of a

volcanic mountain is called a caldera. Ex. Crater Lake, Oregon

from collapse of the volcano Mount Mazama.

Volcanic Landforms - Guide For Reading Page 2