This GeoStory provides a brief introduction to volcanoes, including where and how they form, and some common types. The GeoStory also describes volcanic hazards and monitoring methods, as well as the role volcanoes have played in creating important natural resources and interactions between volcanoes and climate. Finally, the story presents archaeological evidence for early human encounters with volcanoes. Each storypoint uses a specific geographic location and example. New terms are defined in the text. Each storypoint begins with a probing question. Teachers should consider beginning each storypoint by having students discuss the question and state what they already know about the topic. Students should then return to these questions at the end of the lesson to discuss what they have learned.

  1. How did the volcanoes of the Cascade Mountains, in Washington and Oregon, form?

  2. How do calderas form?

  3. How did the Hawaiian Islands form?

  4. What volcanic deposits are cinder cones made of?

  5. What is the most dangerous volcanic hazard for people living near a volcano?

  6. Can scientists predict volcanic eruptions?

  7. How do volcanoes affect the soil?

  8. If the Antarctic Ice Sheet melted quickly, how might volcanoes there be affected?

The 1980 eruption of Mount St. Helens, in Washington State, caused nearly $1 billion worth of damage. Losses to the forestry industry and the cost of clean-up amounted to about 85% of the total cost.

Gold that is present in magma rises to Earth's surface during volcanic eruptions. The famous gold deposits in California were created by volcanic activity in the Sierra Nevada Mountains.

The Hawaiian Islands are formed by a hot spot of magma beneath the Pacific Plate. As the plate moves, the hot spot makes new volcanoes in the chain.

Early pioneers made note of Crater Lake's exceptionally blue color. Crater Lake is very deep, and its water is very clear. This allows sunlight to penetrate to great depth, resulting in the intense blue color.

There are about 1,500 potentially active volcanoes in the world today, not including the ones underwater. Most of these active volcanoes are part of the Pacific Ring of Fire.

active volcano
Noun

volcano that has had a recorded eruption since the last glacial period, about 10,000 years ago.

asteroid
Noun

irregularly shaped planetary body, ranging from 6 meters (20 feet) to 933 kilometers (580 miles) in diameter, orbiting the sun between Mars and Jupiter.

Noun

layers of gases surrounding a planet or other celestial body.

Noun

large depression resulting from the collapse of the center of a volcano.

cinder
Noun

tiny bits of coarse lava.

cinder cone
Noun

hill created by tiny bits of lava blown out of a volcano and fallen down around the volcanic vent. Also called a scoria cone.

comet
Noun

celestial object made up of ice, gas, and dust that orbits the sun and leaves a tail of debris.

composite volcano
Noun

steep volcano made of hardened lava, rock, and ash. Also known as a stratovolcano.

cyanobacteria
Noun

type of aquatic bacteria that can photosynthesize light to create energy. Also called blue-green algae (even though it is not algae) and (in freshwater habitats) pond scum.

earthquake
Noun

the sudden shaking of Earth's crust caused by the release of energy along fault lines or from volcanic activity.

feedback loop
Noun

cycle of causes and effects where the effects either directly reinforce (in a positive feedback loop) or oppose (in a negative feedback loop) the original condition.

Global Positioning System (GPS)
Noun

system of satellites and receiving devices used to determine the location of something on Earth.

lava
Noun

molten rock, or magma, that erupts from volcanoes or fissures in the Earth's surface.

Noun

outer, solid portion of the Earth. Also called the geosphere.

Noun

molten, or partially melted, rock beneath the Earth's surface.

pumice
Noun

type of igneous rock with many pores.

Noun

current of volcanic ash, lava, and gas that flows from a volcano.

seamount
Noun

underwater mountain.

shield volcano
Noun

large, gently sloping volcano made from fluid lava.

stratosphere
Noun

level of Earth's atmosphere, extending from 10 kilometers (6 miles) to 50 kilometers (31 miles) above the surface of the Earth.

stratovolcano
Noun

steep volcano made of hardened lava, rock, and ash. Also known as a composite volcano.

supervolcano
Noun

volcano capable of ejecting more than 1,000 cubic kilometers (240 cubic miles) of material.

tectonic plate
Noun

massive slab of solid rock made up of Earth's lithosphere (crust and upper mantle). Also called lithospheric plate.

tephra
Noun

solid material ejected from a volcano during an eruption.

viscosity
Noun

measure of the resistance of a fluid to a force or disturbance.

Noun

an opening in the Earth's crust, through which lava, ash, and gases erupt, and also the cone built by eruptions.