Volcanoes

Volcanic landforms

Effusive eruptions (gentle flows, lots of lava)• cinder cones • shield volcanoes • plateau basalts

Explosive eruptions (viscous lava, trapped gases)• composite volcanoes• calderas

Cinder coneBig Cinder Butte, Craters of the Moon, Idaho

- forms small hills, less than 450 m high

- black scoria rock with air bubbles

Shield volcanoMauna Loa, Hawaii

•

Low viscosity magmaGases readily escape From this magma

Effusive eruptions

Kilauea, Hawaii

Hot spot

Seamounts

Plateau basalts

Composite volcano

Shield/Composite Comparison

Mount St. Helens: the day before

Flooding (from steam-melted ice and snow)

Four years later

CalderaCrater Lake, Oregon

windblown ash landed in Calgary

6600 years ago

Volcanic hazards and effects

• hot ash (pyroclastics)• steam and gas explosions• lava flows• poisonous gases (carbon dioxide, sulfuric acid)• landslides• tree blowdowns• lahars (steam-melted ice and snow cause flooding

and large mudflows)• increase in atmospheric dust (decreased global

temperatures)

Volcanic benefits

• new fertile soils

- Hawaii, Philippines

• geothermal energy

- Iceland, Italy, New Zealand

• new real estate

- Iceland, Japan, Hawaii

Diamond-bearing kimberlite pipe