Do Now:

• Are volcanoes a destructive or constructive force on the Earth? Explain your answer.

• Answer: Both, Volcanoes are considered destructive as well as constructive because they build up new landforms and destroy existing structures.

7-4 Volcanic Landforms

1) What landforms are created by lava and ash?

2) What are the types of volcanoes?

3) What are some positive aspects of volcanoes?

Landforms from Lava and Ash

Shield Volcanoes

• Shield volcanoes form from the repeated eruption of lava (usually pahoehoe).

• Shield volcanoes tend to be shorter and wider than other types of volcanoes.

Cinder Cone Volcanoes

• Cinder cone volcanoes form from eruptions of high viscosity lava (Aa).

• Cinder cone volcanoes are composed of ash, cinders, and bombs.

• These volcanoes tend to be tall with steep sides.

Composite Volcanoes

• Composite volcanoes form when eruptions alternate between eruptions of ash and lava. (Quiet and Explosive eruptions)

• Composite volcanoes are tall and cone shaped.

Lava Plateaus

• Lava plateaus form from thin runny lava (pahoehoe) erupting from long cracks in the ground.

• Repeated eruptions forms a high flat landform called a Lava Plateau.

Volcanic Neck

• Volcanic necks form when magma hardens in the volcano’s pipe and the rest of the volcano is eroded away.

Volcanic Neck

Landforms from Magma

Sills and Dikes

• Magma that forces its way across rock layers hardens into a dike

• Magma that squeezes between horizontal layers of rock forms a sill

Batholiths

Batholith

• A batholith is a mass of rock formed when a large amount of magma cools beneath the surface.

Dome Mountains

• When a batholith is pushed up to the surface it can form dome mountains.

Are there positive aspects of Volcanoes?

Positive aspects of Volcanoes

• Hot Springs• Geysers• Fertile Soil • Lava breaks down into

mineral rich soil• Geothermal Energy

is used to produce electricity and to heat homes.

Geothermal Energy

Geothermal Heating