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volcanism notes


Types of Volcanoes

There are many types of volcanoes:

Shield Volcano

- A gently-sloping volcano that emits mostly basaltic lava (very fluid lava) that flows in long-lasting, relatively gentle eruptions - explosions are minimal. Shield volcanoes can be very big. An example is Mt. Kilauea (in Hawaii, USA).

Composite or Strato Volcano

- A steep-coned volcano that explosively emits gases, ash, pumice, and a small amount of stiff, silica lava (called rhyolite). This type of volcano can have eruptions accompanied by

lahars -- deadly mudflows. Most volcanoes on Earth are of this type. Stratovolcanoes kill more people than any other type of volcanoes - this is because of their abundance on Earth and their powerful mudflows. Examples are Krakatoa in Indonesia, Mt. Pinatubo in the Philippines, and Mt. St. Helens in

Washington state, USA.

Lava Dome

- A bulbous (rounded) volcano that forms when very viscous lava barely flows. An example is Mount Pelée in Martinique.

Cinder Cone

- A cone-shaped volcano whose steep sides are formed by loose, fragmented cinders that fall to the Earth close to the vent. The lava flows through a single vent that is usually only up to about

1,000 feet tall. There is usually a bowl-shaped crater at the top. As the gas-filled lava erupts into the air, the lava fragments into pieces and forms cinders.

Rhyolite Caldera Complex

- these are the most explosive volcanoes. They do not look like common volcanoes -- after an eruption, the result is a caldera (crater) caused when the area around the vent collapses. Examples are Yellowstone in Wyoming, USA and Lake Taupo in New Zealand (which erupted around A.D. 80).

Volcanoes A-Z

Aa Lava that carries lumps of solid rock called clinker.

Active volcano A volcano that has recently erupted.

Ash Lava that has been blown to powder by the force of an eruption. Ash clouds can reach up to 40 kilometres (25 miles) into the sky.

Basalt A dark grey igneous rock. The entire ocean crust and much of the Earth’s solid surface is made of basalt.

Batholith A large mass of igneous rock formed when an upwelling of magma spreads through rocks underground, but never reaches the surface. It may be revealed later when erosion wears away the rocks above it.

Caldera A large, deep hole formed when a volcano collapses in on itself after a violent eruption.

Crater A circular, funnel-shaped opening at the summit of a volcano.

Dormant volcano A volcano that has stopped erupting, but which may burst into life again in the future.

Mount St Helens in the USA was a dormant volcano that came back to life spectacularly in 1980.

Eruption The blasting out of lava, ash or pumice from a volcano into the air or on to the Earth’s surface.

As pressure in the magma beneath the Earth’s crust builds up, it forces its way up through cracks and erupts at the surface as lava. If the magma is quite runny, the gas contained in it can escape easily. The lava oozes out of the opening and flows down the sides of the volcano. If the magma is thick and sticky, the gas cannot escape, but builds up until it explodes. Huge clouds of gases and ash fly high up into the air.

Extinct volcano A volcano that has not erupted for tens of thousands of years.

Fissure A large crack or opening in the Earth’s crust. Lava may emerge through a fissure without an explosive eruption. Undersea volcanoes are fissures in the seabed.

Fumarole An opening in the Earth's crust, usually close to volcanoes, through which steam and gases are blasted out under pressure.

Geyser A natural fountain of hot water or steam that periodically ejects from an opening in the Earth’s crust. Geysers erupt when underground water comes into close contact with hot, volcanic rocks.

Granite A hard, pink-grey igneous rock, made up of large, clearly visible crystals.

Hot spot A weakness in the Earth’s crust where magma is liable to force its way through. Over time, solidified lava builds up and may eventually break the surface of the ocean. The Hawaiian Islands, for example, are the summits of volcanoes rising from the floor of the Pacific Ocean.

Igneous rock A type of rock formed when magma rises to the Earth’s surface and solidifies. Intrusive igneous rock, such as granite, is formed when magma solidifies beneath the ground. Extrusive igneous rock, such as basalt, is formed when it solidifies above the ground.

Laccolith A dome of igneous rock that lies between layers of sedimentary rock. It is formed when magma pushes between the sedimentary rock strata.

Lava Magma that has erupted at the Earth’s surface through volcanoes. It may flow as hot, molten rock for a while, but then quickly cools and solidifies. Lavas vary from thick to runny, according to the amount of gas contained within them and the type of silicates they are made of.

Magma chamber An underground pool of magma. Over time, pressure in the chamber builds up, forcing magma to push through cracks in the Earth’s crust. Many volcanoes are situated above a magma chamber.

Magma Hot, molten rock beneath the Earth’s surface. Magma is formed in the Earth’s mantle. It is composed mostly of silicates, with gases contained in bubbles.

Obsidian A dark, glassy rock formed when lava cools down so quickly that its minerals do not have time to crystallize.

Pahoehoe Very runny lava that flows beneath a hardening, rocky crust. On cooling, it has a smooth, billowy texture and rope-like appearance.

Pele's hair Volcanic glass fibres formed when particles of molten rock are erupted and spun out by the wind into long, hair-like strands. It is named after Pele, the Hawaiian goddess of volcanoes.

Pillow lava Runny lava that erupts under the sea and hardens into round, pillow-shaped lumps of rock.

Pumice A volcanic glass “froth” formed from cooling, gassy lava. It contains numerous bubbles.

Pyroclastic flow The extremely hot mixture of volcanic rock and gases that sweeps down a volcano’s slopes at more than 300 km/h (200 mph), destroying everything in its path. The residents of Pompeii were wiped out by a pyroclastic flow when Mt Vesuvius erupted in AD 79.

Ring of Fire An area surrounding the Pacific Ocean where large numbers of earthquakes and volcanic eruptions occur. There are 452 volcanoes in the Ring of Fire, about 75% of all the world's active and dormant volcanoes.

Shield volcano A large volcano with gently sloping sides. Shield volcanoes build up over time from repeated lava flows. They erupt thin, runny lava.

Silicates Types of mineral that contain silicon and oxygen. Silicates make up more than 90% of the rocks in the Earth’s crust. Thin, runny magmas consist of different types of silicates to those that make up thick, viscous magmas.

Stratovolcano A tall, steep, cone-shaped volcano. Stratovolcanoes are formed from layers of volcanic lava, built up by multiple eruptions over hundreds of thousands of years. They erupt ash, pumice and thick, viscuous lava. Stratovolcanoes are the most common type of volcano.

Tuff A type of rock made of volcanic ash welded together. It was used by the Romans to make many buildings and bridges, and by the natives of Easter Island to make their famous statues.

Vent An opening in the Earth’s surface through which lava and gases seep out.

Viscosity A measure of the fluidity of magma and lava (and other liquids). Thick lava is more viscous than thin, runny lava.

Volcano A volcano is an opening, or vent, in the Earth’s crust through which magma, molten rock, erupts. The word volcano is usually used to describe a cone-shaped mountain with a central vent and a crater at the summit, but this is not always the case. Many volcanoes have gently spreading slopes.

Others are simply cracks in the ocean bed. Most volcanoes are situated along the edges of the giant tectonic plates that make up the Earth’s surface. More than half of the world’s active volcanoes above sea level encircle the Pacific Ocean to form the so-called “Ring of Fire”.


A volcano is a place on the Earth's surface (or any other planet's or moon's surface) where molten rock, gases and pyroclastic debris erupt through the earth's crust. Volcanoes vary quite a bit in their structure - some are cracks in the earth's crust where lava erupts, and some are domes, shields, or mountain-like structures with a crater at the summit.

Magma is molten rock within the Earth's crust. When magma erupts through the earth's surface it is called lava. Lava can be thick and slow-moving or thin and fast-moving. Rock also comes from volcanoes in other forms, including ash (finely powdered rock that looks like dark smoke coming from the volcano), cinders (bits of fragmented lava), and pumice (light-weight rock that is full of air bubbles and is formed in explosive volcanic eruptions - this type of rock can float on water).

Volcanic eruptions can cause great damage and the loss of life and property.

The Word Volcano:

The word volcano comes from the Roman god of fire, Vulcan. Vulcan was said to have had a forge (a place to melt and shape iron) on Vulcano, an active volcano on the Lipari Islands in Italy.

Extreme Volcanoes:

The largest volcano on Earth is Hawaii's

Mauna Loa

. Mauna Loa is about 6 miles (10 km) tall from the sea floor to its summit (it rises about 4 km above sea level). It also has the greatest volume of any volcano, 10,200 cubic miles (42,500 cubic kilometers). The most active volcano in the continental USA is

Mt. St. Helens

(located in western Washington state).

The largest volcano in our Solar System is perhaps

Olympus Mons

on the planet Mars. This enormous volcano is 17 miles (27 km) tall and over 320 miles (520 km) across.

Volcano Quiz Printout

Circle the right answer:

1. What is the name of molten rock that erupts from volcanoes? MAGMA - LAVA - VENT

2. What is the name of molten rock within the Earth's crust? MAGMA - LAVA - VENT

3. What is the name of the tube through which molten rock flows? PARASITIC - CONDUIT - BASE

4. In which part of the Earth would you find a magma reservoir? CRUST - PARASITIC - CONDUIT

5. Composite volcanoes are made up of layers of lava and ______. CONDUIT - ASH – MAGMA

6. What is the name of a smaller vent-structure on the side of some volcanoes? SUMMIT - MAGMA


7. What is the name of the bowl-like opening of a volcano? SILL - CRATER - ASH

8. Are ash clouds emitted from sills? YES - NO

9. What is the name of an opening through which molten rock and gases escape from a volcano?


10. The sides of a volcano are called its flanks. YES – NO

Earth Science

- Volcanoes - Quiz Questions

Q1-1: What is the difference between magma and lava?

Magma is underground melted rock. Lava is magma that has reached Earth’s surface and cooled.

Q1-2: Imagine a volcano with only one vent. What change might cause a second vent to appear on the side of the volcano?

A second vent could appear on the side of the volcano if a still or dike broke through to the surface.

Q1-3: About 7,000 years ago, Mount Mazama erupted and the summit (top) of the volcano collapsed forming a depression that was filled with rain and melted snow. The depression is now called Crater Lake.

Mount Mazama is an extinct volcano. What is the best term to describe the depression that holds Crater


A1-3: The depression is called a caldera.

Q1-4: Which kind of volcano is being described below? Use one of these terms: active, dormant, or extinct.

a. No longer erupting;

b. Could be described as “sleeping”; c. May erupt in the future but is not erupting at present or recently; d. Erupting on a regular basis; e. The volcano is eroding and a volcanic rock is exposed.

A1-4: A. extinct B. Dormant C. Active E. extinct

Q1-5: What is the difference between a dormant volcano and an active volcano?

A1-5: A dormant volcano is not currently active, but may become active in the future. An active volcano is erupting or has erupted recently and is expected to erupt again in the near future.

Q1-6: Based on your reading in this section, answer these questions:

a. Under what conditions of temperature and pressure does a solid rock begin to melt? b. Under what conditions of temperature and water content does a solid rock begin to melt?

A1-6: A rock begins to melt at low temperature and high water content –or- a rock begins to melt at high temperature and low water content.

Q2-1: What did early map makers notice about the locations of volcanoes?

A2-1: Volcanoes were located along coastlines.

Q2-2: What causes the region called the Ring of Fire?

A2-2: The Ring of Fire is caused by subduction of the Pacific Plate under other plates.

Q2-3: If you could melt a piece of quartz in some lava, would the lava get more sticky or less sticky?

Explain your answer.

A2-3: Adding this mineral to lava makes it stickier.

Q5-24: What is the difference between a pyroclastic flow and a lahar?

A5-24: When a column of exploding material collapses, it races down the side of a mountain as a pyroclastic flow. A lahar is a mud flow that accompanies a composite volcano eruption.

Q5-25: How do igneous rocks form?

A5-25: From cooling of magma or lava

Q5-26: What about the appearance of an igneous rock gives you a clue about whether it cooled slowly or quickly?

A5-26: slow cooling = large crystals; fast cooling = small crystals

Q5-27: Math Problem: The speed of a pyroclastic flow is 100 km/hr. How far would this flow travel in 10 minutes? (Show your work – not just the answer! Hint: Begin by converting 100 km/hr to ? km/min first.)

A5-27: 100 km/hr divided by 60 = 1.67 km/min (x) 10 min. = 16.67 km distance

Q6-1: What is volcano?

A6-1: An erupting vent through which molten rock reaches Earth’s surface or a mountain built from the products of an eruption.

Q6-2: magma?

A6-2: Underground melted rock

Q6-3: magma chamber?

A6-3: A location where magma collects inside Earth

Q6-4: conduit?

A6-4: Central internal vertical shaft that carries magma up inside a volcano

Q6-5: vent?

A6-5: An opening to the surface where magma leaves the volcano conduit

Q6-6: dike?

A6-6: An upward-slanting sheet of magma within a volcano

Q6-7: sill?

A6-7: The sideways movement of magma underground inside a volcano

Q6-8: lava ?

A6-8: Magma that has reached and cooled on Earth’s surface

Q6-9: caldera ?

A6-9: A bowl-shaped vent of a volcano after it has erupted

Q6-10: resurgent dome

A6-10: A mound in the vent of an erupted volcano

Q6-11: lava lake ?

A6-11: A lake that contains lava that has formed in a caldera

Q6-12: active volcano?

A6-12: A volcano that is erupting or has erupted recently

Q6-13: dormant volcano?

A6-13: A volcano that is not erupting now, but that may erupt in the future

Q6-14: extinct volcano?

A6-14: A volcano that no longer erupts and is in the process of eroding

Q6-15: volcano neck?

A6-15: Solid remains of magma that filled the conduit of an extinct volcano. The neck is exposed as the volcano erodes.

Q6-16: Ring of Fire?

A6-16: A region of Earth’s plate boundaries where oceanic crust is subducting under other plates

Q6-17: basalt?

A6-17: A dense, oceanic, dark-colored rock that is NOT silica rich

Q6-18: silica?

A6-18: Like the mineral quartz, it makes magma thick and sticky

Q6-19: pillow lava?

A6-19: Runny basaltic lava that oozes out at a mid-ocean ridge and cools quickly in water

Q6-20: volcanic island?

A6-20: A volcano that forms away from a plate boundary on an oceanic plate

Q6-21: hot spot?

A6-21: The top of an established mantle plume

Q6-22: volcanic island chain?

A6-22: A series of volcanoes formed by a hot spot as a lithospheric plate moves over the hot spot

Q6-23: mantle plumes?

A6-23: Narrow channels of magma that rise up through the mantle

Q6-24: Loihi?

A6-24: A new volcanic island forming underwater next to Kilauea in Hawaii

Q6-25: island arc?

A6-25: A string of volcanic islands that forms close to a plate boundary

Q6-26: subduction zone?

A6-26: An area where denser basaltic oceanic plates dive under less dense continental plates

Q6-27: shield volcano?

A6-27: Low silica magma producing a wide, flat volcano

Q6-28: cinder cone?

A6-28: A pile of rock bits that forms on the sides or in the caldera of a volcano

Q6-29: fire fountain?

A6-29: A high gas magma eruption

Q6-30: composite volcano?

A6-30: A tall, explosive, cone- shaped volcano formed by layers of silica-rich lava and ash

Q6-31: pyroclastic flow?

A6-31: A destructive cloud of volcanic material that moves quickly down the side of a volcano after an explosive eruption

Q6-32: lava bombs?

A6-32: Blobs of glowing lava thrown from an explosive eruption

Q6-33: lahar?

A6-33: A mudflow that results from a volcanic eruption

Q6-34: water cycle?

A6-34: A set of processes energized by the Sun that keeps water moving from place to place on Earth

Q6-35: geologic cycle?

A6-35: A set of processes that keeps rocky material moving from place to place on Earth

Q6-36: geysers?

A6-36: An explosive eruption of water from volcanic-heated underground chambers

Q6-37: hot springs?

A6-37: Volcanic-heated water that rises to the surface in pools

Q6-38: igneous rocks?

A6-38: Rocks that are formed from magma or lava

Q6-39: granite?

A6-39: Light-colored igneous rock with large, visible quartz and feldspar crystals made from silica-rich magma

Q6-40: gabbro

A6-40: A type of rock made from silica-poor magma (has large crystals)

Q6-41: obsidian?

A6-41: Volcanic glass – cools quickly & has no crystals

Q6-42: welded tuff?

A6-42: Orange-tan in color; left over from a pyroclastic flow

Q6-43: weathering?

A6-43: The process of breaking down rocks

Label the Volcano Diagram

Read the definitions, then label the diagram below.

Definitions ash cloud - an ash cloud is the cloud of ash that forms in the air after some volcanic eruptions. conduit - a conduit is a passage through which magma (molten rock) flows in a volcano. crust - the crust is Earth's outermost, rocky layer. lava - lava is molten rock; it usually comes out of erupting volcanoes. magma chamber - a magma chamber contains magma (molten rock) deep within the Earth's crust. side vent - a side vent is a vent in the side of a volcano. vent - a vent is an opening in the Earth's surface through which volcanic materials erupt.

Close Activity

Fill in the blanks below using words from the word bank.

Word Bank:

Mars cracks crust

Magma crater

Earth miles volcano summit erupts rock lava

A volcano is a place on the Earth's surface (or any other planet's or moon's surface) where molten

_______________________, gases and pyroclastic debris erupt through the earth's

_______________________. Volcanoes vary quite a bit in their structure - some are

_______________________ in the earth's crust where lava erupts, and some are domes, shields, or mountain-like structures with a _______________________ (a circular depression) at the summit.

_______________________ is molten rock within the Earth's crust. When magma

_______________________ through the earth's surface it is called _______________________.

The largest volcano on _______________________ is Hawaii's Mauna Loa. Mauna Loa is about 6 miles

(10 km) tall from the sea floor to its _______________________ (it rises about 4 km above sea level). It also has the greatest volume of any volcano on Earth, 10,200 cubic miles (42,500 cubic kilometers).

The largest _______________________ in our Solar System is perhaps Olympus Mons on the planet

_____________________. This enormous volcano is 17 _____________________ (27 km) tall and over

320 miles (520 km) across.

Volcano Craft

Make a mock volcano that erupts when you mix baking soda and vinegar.

This is a very messy project - especially at the end when the volcano erupts. Wear old clothes and work on a pile of newspapers (or even better, outdoors).

In a real volcano, molten rock from deep within the Earth erupts through a volcano (the molten rock is called magma when it is within the Earth and is called lava when it comes out of a volcano). In this project, a mock volcano will erupt with a bubbly, fizzy liquid that is created by a simple chemical reaction.

This project shows kids what happens when an acid (vinegar) and a base (baking soda) interact.

Chemically, the acid and base neutralize each other, producing carbon dioxide gas as a byproduct. The exact reaction is:

HC2H3O2 (vinegar = acetic acid) + NaHCO3 (baking soda = sodium bicarbonite) = CO2 (carbon dioxide

gas) + NaC2H3O2(sodium acetate) + H2O (water)


Old aluminum pie tin (or baking pan or paper plate)

Lots of old newspaper

Baking soda (about 3-4 tablespoons)

Vinegar (about 1/2 cup)

A few drops of liquid dishwashing detergent

Small plastic bottle (like a small pop bottle)

Modeling clay (for a clay recipe, click here)


Measuring spoon and measuring cup

Red food coloring

Glitter (optional)

Put the clean, empty bottle on the aluminum pie plate (or baking pan or paper plate).

Using the modeling clay, make a volcano around the bottle. Leave the area around the top of the bottle open and don't get any clay inside the bottle.

You can decorate the volcano with little twigs, lichens (that look like tiny trees), etc.

Using the funnel (make sure it's dry), put 3 to 4 tablespoons of baking soda into the bottle. Then add a few drops of liquid dishwashing detergent and about a half cup of water.

Optional: add a little bit of glitter (about half a teaspoon).

Put a few drops of red food coloring into about one-half of a cup of vinegar.

The Eruption: Using the funnel, pour the vinegar mixture into the bottle

(then quickly remove the funnel).

Your volcano will erupt immediately! When the vinegar reacts with the baking soda, carbon dioxide gas is formed and the bubbles push the "lava" out the "volcano." Be prepared for a mess!

Label: The Ring of Fire

Label the oceans and continents on the map below. Then, draw the location of the ring of fire on the map in red.


The area encircling the Pacific Ocean is called the " Ring of Fire ," because its edges mark a circle of high volcanic and seismic activity (earthquakes). Most of the active volcanoes on Earth are located on this circumference. On the periphery of the Pacific Ocean, the edge of the Pacific Continental Plate is expanding in the seabed, and is hitting the North American Plate, the Nazca Plate, the Eurasian Plate, and other plates, causing the margins of the plates to collide, buckle, and compress, causing earthquakes and volcanoes

Antarctic Plate - the plate around the South Polar region.

Caribbean Plate - the small plate underlying the Caribbean Sea.

Cocos Plate - the small plate south of Mexico

Eurasian Plate - the plate under Asia and Europe.

Indo-Australian Plate - the plate beneath Australia, the eastern Indian Ocean, and the southwestern

Pacific Ocean

Nazca Plate - the small plate just west of South America.

North American Plate - the plate underlying North America

Pacific Plate - the plate beneath most of the Pacific Ocean.

Philippine Plate - the small plate under the western Pacific Ocean (north of Australia).

South American Plate - the plate underlying South America.

Name_____________________________________________________ Yr & Section_______________

Volcano: Illustrated Acrostic Poem

Draw a picture of a volcano, then write an acrostic poem about it. Start each line of your poem with the letter on that line.