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Skills Worksheet
Directed Reading A
Section: Causes of Volcanic Eruptions
coming
1. To help predict eruptions, scientists study from active
volcanoes and look for changes in the volcano’s
.
THE FORMATION OF MAGMA
____
__
2. The rock of the Earth’s mantle a. flows very quickly.
b. has a puttylike consistency. c. is cooler than the
Earth’s crust. d. is solid and rock-hard.
____
__
3. Rock usually melts to form magma a. when there is
an increase in pressure. b. when there is a decrease in
pressure. c. when there is a decrease in temperature. d.
when it is in a volcano.
4. Magma forms in the deeper regions of the Earth’s
and the uppermost layers of the
.
cause
5. Changes in and magma to form. 6. How does magma behave
like air bubbles in a jar of honey?
c. crater column.
a. divergent boundary.
b. mantle rock.
d. rift zone.
11. Tectonic plates separate at a(n)
boundary.
on the right more than once.
______24. have not erupted in thousands of years
a. active volcano
WHERE VOLCANOES FORM ______ 7. About 80% of active
b. dormant volcano
______25. have not erupted recently
volcanoes on landjoin.
formc.where
c. extinct volcano
collide.plates
______26. are erupting
now
separate. d. slide past each other.
______27. probably won’t erupt again
8. Tectonic plate boundaries are areas where tectonic plates , , or .
______28. will probably erupt sometime in the
future
______29. will probably erupt in the near future
Copyright © by Holt, Rinehart and Winston. All rights reserved.
Directed Reading A continued
9. Why are the plate boundaries surrounding the Pacific Ocean called the
Ring of Fire?
WHEN TECTONIC PLATES SEPARATE ______10. A set of
rifts between separating plates is called a(n)
Section: Causes of Volcanic Eruptions
1. To help predict eruptions, scientists study from active
volcanoes and look for changes in the volcano’s
coming
.
Place
the following steps of mid-ocean ridge formation in the correct order. Write the
appropriate number in each space provided.
THE FORMATION OF MAGMA
______
Magma
rises
surface
of thea.surrounding
rock.
____ 12. 2.
The rock
of to
thethe
Earth’s
mantle
flows very quickly.
__
b. has a puttylike consistency. c. is cooler than the
______13. Mantle material rises to fill the spaces between plates.
Earth’s crust. d. is solid and rock-hard.
______14. The magma forms a new crust on the ocean floor.
______15. A rift forms as tectonic plates move apart.
____
3. Rock usually melts to form magma a. when there is
______
Theincrease
mantle in
rock
melts because
the decrease
in pressure.
__ 16. an
pressure.
b. whenofthere
is a decrease
in
pressure. c. when there is a decrease in temperature. d.
WHEN TECTONIC PLATES COLLIDE
when it is in a volcano.
______ 17. Subduction is
the movement of one tectonic plate against another.
4. Magma forms in the deeper regions of the Earth’s
the movement of one tectonic plate over another.
the layers
movement
of one tectonic plate under another.
and the uppermost
of the
.
the movement of one tectonic plate away from
cause
another.
______18. Convergent boundaries commonly exist where
5. Changes in and
magma
to form.
Howbydoes
magma behave
tectonic
plates
move6.side
side.
like air bubbles oceanic
in a jar crust
of honey?
moves away from continental crust.
c. crater under
column.
continental crust is subducted
oceanic
a. crust.
divergent boundary.
b. mantle
rock.
d. rifteach
zone.
tectonic
plates collide with
other.
______19. As the ocean crust sinks deeper into the mantle,
11. Tectonic plates separate at a(n)
boundary.
it increases in
temperature.
on the right more than once.
it forms a lava fountain.
______24. have not
erupted
in thousands of years
a. active volcano
it forms
a volcano.
its pressure decreases.
______25. have not erupted recently
Copyright © by Holt, Rinehart and Winston. All rights reserved.
______26. are erupting now
______27. probably won’t erupt again
b. dormant volcano
c. extinct volcano
Directed Reading A continued
20. The oceanic crust is and
than the continental crust.
HOT SPOTS
______21. The Hawaiian Islands are located
along a tectonic plate
boundary.
far from any plate boundary.
over a lava fountain.
on lava plateaus.
22. What are hot
spots?
23. Some scientists believe that hot spots form
along in the Earth’s crust.
PREDICTING VOLCANIC ERUPTIONS Match each volcano type listed on the right
with the correct description listed on the left. Write the letters in the space provided.
You may use the volcanoes listed
Section: Causes of Volcanic Eruptions
coming
1. To help predict eruptions, scientists study from active
volcanoes and look for changes in the volcano’s
.
THE FORMATION OF MAGMA
____
__
2. The rock of the Earth’s mantle a. flows very quickly.
b. has a puttylike consistency. c. is cooler than the
Earth’s crust. d. is solid and rock-hard.
30. Just before an eruption, the number and intensity of small
earthquakes .
____
3. Rock usually melts to form magma a. when there is
31. Changes in the ratio of sulfur dioxide to carbon dioxide may indicate
__
an increase in pressure. b. when there is a decrease in
changes in the below.
pressure. c. when there is a decrease in temperature. d.
when it is in a volcano.
32. Small changes in a volcano’s slope can be detected by
a(n) .
4. Magma forms in the deeper regions of the Earth’s
and the uppermost layers of the
.
Copyright © by Holt, Rinehart and Winston. All rights reserved.
5. Changes in and magma to form. 6. How does magma behave
cause
Directed Reading A continued
33. What are three ways scientists predict volcanic
explosions?
34. What might cause a bulge in the slope of a
volcano?
Copyright © by Holt, Rinehart and Winston. All rights reserved.