Download Volcano Reading and questions

Volcano Reading and questions
A volcano is a weak spot in the crust where molten material, or magma, comes to the surface. Magma is a molten
mixture of rock-forming substances, gases, and water from the middle mantle. When magma reaches the surface, it is
called lava. When lava has cooled, it forms solid rock. Lava released during volcanic activity builds up Earth’s surface.
Volcanoes occur in belts that extend across continents and oceans. One major volcanic belt is the Ring of Fire, formed
by the many volcanoes that rim the Pacific Ocean. Volcanic b e l t s form along the boundaries of Earth's plates. At
plate boundaries, huge pieces of the crust diverge (pull apart) or converge (push together). As a result, the crust often
fractures, allowing magma to reach the surface. Most volcanoes form along diverging plate boundaries such as midocean ridges and along converging plate boundaries where subduction takes place. Along the rift valley, lava pours out
of cracks in the ocean floor, gradually building new mountains.
Many volcanoes form near converging plate boundaries where oceanic plates return to the mantle. Volcanoes may form
where two oceanic plates collide or where an oceanic plate collides with a continental plate. Many volcanoes occur
near boundaries where two oceanic plates collide. Through subduction, the older, denser plate sinks beneath a deepocean trench into the mantle. Some of the rock above the sub-ducting plate melts and forms magma. Because the
magma is less dense than the surrounding rock, it rises toward the surface. Eventually, the magma breaks through the
ocean floor, creating volcanoes. The resulting volcanoes create a string of islands called an island arc. Volcanoes also
occur where an oceanic plate is subducted beneath a continental plate.
Some volcanoes result from “hot spots” in Earth’s mantle. A hot spot is an area where material from within the mantle
rises and then melts, forming magma. A volcano fo rm s above a hot spot when magma erupts through the crust
and reaches the surface. A hot spot in the ocean floor can gradually form a series of volcanic mountains. The Hawaiian
Islands formed one by one over millions of years as the Pacific plate drifted over a hot spot. Hot spots can also form
under the continents. Yellowstone National Park in Wyoming marks a hot spot under the North American plate.
Questions:
What is a volcano? __________________________________________________________________________________
A molten mixture of rock forming substances, gases and water from the mater is referred to as __________________.
When magma reaches the surface it is called, _____________________.
Where do most volcanoes form? _______________________________________________________________________
What is the ring of fire?_______________________________________________________________________________
Where is it located?__________________________________________________________________________________
What is a hot spot? __________________________________________________________________________________
Where is there a hot spot on the continental crust? _______________________________________________________
How did the Hawaiian Islands form? ____________________________________________________________________
Volcanoes at boundaries where two oceanic plates collide create a string of islands called a _______________________.
1. T or F – Most volcanoes of the mid ocean ridge rise above the ocean’s surface.
2. T or F – Many volcanoes form near converging plate boundaries where oceanic crust returns to the mantle.
3. T or F – Magma forms in the lithosphere.
4. T or F –Volcanoes can form along diverging plate boundaries on land.
5. T or F – Liquid magma rises until it reaches the surface, or until is become trapped beneath layers of rock.
6. T or F – Hot spots form only under oceanic crust.
Explain how each volcano forms next to the picture. If it forms along a plate boundary, identify the plate boundary type.
Identify the cause of each volcano below using the words: subduction, rift, and hot spot.
a) In 1973, a town in Iceland called Vestmannaeujar was surprised when lava began erupting from a vent or crack in the
Earth’s surface. The Earth’s crust seemed to split apart._______________________
b) Scientists feel that the Cascade Mountains, extending from California to British Columbia, are still forming. Two plates
are colliding, forcing magma up from the mantle to form the mountain. _____________________
c) Mauna Loa in Hawaii is the “growing mountain”. In 1969 and 1974, it erupted and poured out lava through a hole in
the Earth. This lava called and hardened into rock. Below it, molten lava continues to flow. _____________________
Fill in the Blank. Use the words provided below to fill in the blanks in these sentences.
Blast zone
lava dome
magma chamber
pumice
steam explosion
Lava
Magma
organic material
mudflow
A __________________ is usually a rounded and steep sided formation of thick, hardened lava or magma.
An explosive release of steam, usually occurring when water comes into contact with hot rock or magma is called a
___________________________________.
An area of about 230 square miles around Mount St. Helens, the ___________________, was affected by the heat and
force of the lateral blast.
___________________ is a light colored, frothy volcanic rock that may float in water because of the bubbles trapped
inside.
Molten material comes to the surface during an eruption from a ______________________________, an underground
pocket of magma
Use the figure to fill in the correct answer
1. What is the name of molten rock that erupts from volcanoes? ___________________
2. What is the name of molten rock within the Earth's crust? ______________________
3. What is the name of the tube through which molten rock flows? _________________
4. In which layer of the Earth would you find a magma reservoir? ___________________
5. Composite volcanoes are made up of layers of lava and ______________.
6. What is the name of a smaller vent-structure on the side of some volcanoes? _______________________
7. What is the name of the bowl-like opening of a volcano? _____________________
8. What is the name of an opening through which molten rock and gases escape from a volcano?
9. T or F – Ash clouds are emitted from sills.
10. T or F –: The sides of a volcano are called its flanks.
Volcanoes and the Power of Three
Mention volcanoes, and most people picture a tall mountain spewing out red-hot lava like fireworks on
Independence Day. However, that is just one of the three types of volcanoes that exist. Interestingly enough, lava is just
one of the three kinds of material emitted from an erupting volcano. Finally, volcanoes endanger three different entities
in their active state. When it comes to studying volcanoes, remember the power of three.
The most common, well-known type of volcano is the composite volcano. It is a medium-sized mountain with a
steep peak and sloping sides made up of a combination of layers of lava and cinders. It may have one or more vents
throughwhich lava escapes from the magma chambers within the Earth's mantle. Each eruption adds another layer of
material to the volcano that is growing around the vent. Mount Vesuvius in Italy is a composite volcano.
The shield volcano is a large, gently sloping mountain formed by flowing lava that cooled and hardened. Hawaii
boasts many shield volcanoes. A cinder cone volcano is a small volcano, normally less than 1,000 feet tall. They are
made up of lava chunks called cinders.
Did you know that most volcanoes are formed beneath the oceans? In recent decades scientists have been
mapping out the location of volcanoes on the ocean floor. Even so, of all the land volcanoes, an average of 50 to 60 are
active in any given year, with half of them being newly formed. Scientists have watched and recorded the growth of
some new volcanoes!
Active volcanoes erupt with one or more of three different kinds of material. The most well known is lava,
originating from magma - melted rock - in the Earth's mantle. The other two materials are tephra (rock fragments) and
gases. Which type of material erupts from a volcano depends on what the magma inside the volcano consists of.
An erupting volcano may endanger three entities: people, property, and agriculture. The danger of fast-moving,
hot lava rivers is obvious, but there is also danger from explosively erupted materials such as tephra, cinder chunks, and
falling ash. It will destroy everything in its path. The heat from the lava and other volcanic material can kill people,
animals, and plants even from a distance. Clouds of ash and gases can suffocate humans and animals alike. Winds can
carry ash clouds away from the volcano and toward populated areas, putting many lives in danger. That is what
happened in the most famous of eruptions, the eruption of Mount Vesuvius in 79 A.D. that buried the town of Pompeii.
1. Most volcanoes are formed on land.
True False
2. Which of the following statements is true?
A. A composite volcano is a medium-sized volcano made up of layers of cinders and lava.
B. A composite volcano is a large mountain made up of layers of lava.
C. A composite volcano is a small volcano made of cinders.
3. Hawaii is an example of which type of volcano?
A. Composite volcano
B. Shield volcano
C. Cinder cone volcano
4. What are the three types of material that a volcano may emit?
A. Lava, magma, ash
B. Lava, tephra, gases C. Ash, cinders, gases
D. Explosive volcano
D. Animal, vegetable, mineral
5. Which of the following statements is not true?
A. Volcanic eruptions can sometimes bury towns in ash.
B. Volcanic eruptions can cause layers of new material to build up the volcano.
C. Volcanic eruptions may endanger people, property, and agriculture.
D. Volcanic eruptions are a danger only to creatures in the immediate vicinity.
6. The eruption of Mount Vesuvius buried what town in 79 A.D.?
A. Washington
B. Pompeii
C. Rome
D. St. Helens
7. How did people die in the aftermath of the famous Mount Vesuvius eruption?
A. Smothered by ash.
B. Burned by lava.
C. Crushed by falling tephra.
8. Mount St. Helens erupted violently in 1980. On what continent is this volcano found?
A. South America B. Australia
C. North America
D. Europe
D. All of the above