Volcanoes Unit Study Guide

Name______Period______

  1. What is magma?

Molten rock BELOW the surface of the Earth.

  1. Magma that flows onto the Earth’s surface is called lava.
  1. What is a volcano?

Mountain created from repeated lava flows and/or pyroclastic material.

  1. Nonexplosive is the most common type of volcanic eruption.
  1. What would you expect to see during an explosive volcanic eruption?

Clouds of hot ash, gas and debris shoot out of a volcano.

  1. Silica rich magma _____.
  2. Has a thin, runny consistency
  3. Allows gases to escape easily
  4. Causes explosive eruptions
  5. Is rarely associated with explosive eruptions
  1. The more water contained in the magma, the greater/higher/more/betterthe chances an explosive eruption will occur.
  1. The main product of a nonexplosive eruption is lava.
  1. The main product of an explosive eruption is pyroclastic material.
  1. When does pyroclastic material form?

When magma is blasted into the air and hardens.

Match the correct description with the correct term.

  1. __B__ Forms underwater in rounded lumps.A. aa lava
  2. __C__ Flows slowly, like dripping wax.B. pillow lava
  3. __A__ Has a brittle, jagged crustC. pahoehoe lava
  4. __D__ Cool, stiff lava that forms jumbled heapsD. blocky lava
  1. The viscosity of lava tells how thick/fast it is.

Match the correct description with the correct term.

  1. __B__ large blobs of magma that harden in the airA. volcanic blocks
  2. __A__ solid rock blasted out of a volcanoB. volcanic bombs
  3. __D__ glass-like slivers from the walls of exploding gas bubblesC. lapilli
  4. __C__ pebblelike bits of magma that cool in the airD. volcanic ash
  1. What is a pyroclastic flow?

Enormous amounts of hot ash, debris and gas are ejected from a volcano and flow down the volcano.

Match the description with the correct volcano type.

  1. __A__ the largest mountain on Earth.A. shield volcano
  2. __A__ forms from lava, not steepB. cinder cone volcano
  3. __B__ often occurs in clustersC. composite volcano
  4. __C__ forms from alternating layers of pyroclastic material & lava
  5. __B__ made entirely of pyroclastic material
  6. __C__ sometimes called a stratovolcano
  1. A funnel shaped pit around a volcano’s central vent is called a(n) crater.
  1. When the roof over a magma chamber collapses, it forms a caldera.
  1. Craters, calderas and lava plateaus are volcaniclandforms.
  1. A long crack in the Earth’s crust is called a(n) fissure (rift).
  1. After repeated eruptions of lava spread over a large area,lava plateasare formed.
  1. Lava plateaus are created by repeated eruptions.
  1. Describe the rock of the Earth’s mantle.

Solid rock that is under intense heat and pressure that causes it to act like a liquid. (Pliable rock that acts like Play-Doh.)

  1. Magma forms in the deeper regions of the Earth’scrust and the uppermost layers of the mantle.
  1. Changes in heat (temperature) and pressure cause magma to form.
  1. How does magma behave like air bubbles in a jar of honey?

Rise very slowly.

  1. About 80% of active volcanoes form on land where plates collide.
  1. Why are the plate boundaries surrounding the Pacific Ocean called the Ring of Fire?

Because there are so many volcanoes in the area around the Pacific Plate

  1. A set of rifts between separating plates is called a(n) mid-ocean ridge (rift valley).
  1. What are hot spots? What island chain is being created by one?

Volcanically active spot on the Earth’s surface where magma rises that is NOT near a plate boundary.

Hawaiian islands are forming this way.

Match the description with the correct term.

  1. __C__ have not erupted in thousands of yearsA. active volcano
  2. __B__ have not erupted recentlyB. dormant volcano
  3. __A__ are erupting notC. extinct volcano
  4. __C__ probably won’t ever erupt again
  5. __B__ will probably erupt sometime in the future
  6. __A__ will probably erupt in the near future
  1. What are some indications that a volcano will erupt soon?

*Small earthquakes*Change in slope

*Release of gases*Temperature increase

  1. What are 3 ways scientists predict volcanic explosions?

*GPS

*Satellite images

*Tiltmeter

  1. What might cause a bulge in the slope of a volcano?

Rising magma in the volcano.

  1. Why don’t WE experience a volcanic threat in our area?

We aren’t near a tectonic boundary or a hot spot.

Fill in the chart below correctly.

Type of volcano: / What they are composed of: / What type of lava produced: / Explosive or nonexplosive?
Shield volcano / Lava / Mainly runny
Some may be blocky / Nonexplosive
Composite volcano / Lava
Pyroclastic material / Runny / Both
Cinder cone volcano / Pyroclastic material / NONE / Explosive