Volcanoes
The ground that we think of as solid and steady is actually in continuous motion. Sometimes the earth´s surface splits and allows the molten rock beneath to escape as a(n)__________.
Volcano
Two-thirds of active volcanoes are found in an area around the edges of the Pacific Ocean. These volcanoes form a ring that volcanologists call the __________.
Ring of Fire
An earthquake, volcano, or landslide occurring under or near the ocean can cause a series of giant waves called __________.
Tsunami
Sometimes a body of water is located near an underground magma pool. Heat from the hot magma warms the water. Once the water is heated, it rises to the earth´s surface, creating a ______________.
Hot Spring
A ___________ is a hot spring that periodically blows steam and hot water into the air.
Geyser
_______________ have gradually sloping sides and look like upside-down saucers.
Shield Volcano
When a volcano erupts, molten rock, or _______, may suddenly explode through the earth´s surface, scorching and destroying everything in its path. This is the name of the molten rock before it breaks through the surface of the earth.
Magma
The portion of the crust that forms the continents is approximately _______ miles thick.
25
The point on the surface of the earth directly above the focus is called the __________.
Epicenter
_______ are breaks in the earth´s surface along which rock can move.
Faults
A ______________ is usually a volcano that resembles a hill more than a mountain.
Cinder Cone Volcano
A(n) __________ volcano erupted in the distant past and is currently inactive and not expected to erupt again.
Dormant
The crust under the ocean is only about _______ to _______ miles thick.
2 to 4
When the magma breaks the surface, it is called __________.
Lava
A composite cone volcano is made of layers of hardened lava and __________, a mixture of cinders, ash, and rock.
Tephra
The _______________ is the large, symmetrical, cone-shaped volcano that is commonly pictured.
Composite Cone Volcano
A(n) __________ volcano is one that has erupted at some point during a recorded time period and is expected to erupt again.
Active
Seismologists use a machine called a __________ to detect, time, and measure the movements of the earth.
Seismograph
A hot spring that contains more mud than water is called a __________.
Mud Pot
The ground that we think of as solid and steady is actually in continuous motion. Sometimes this movement causes large shifts in the earth´s surface, resulting in a(n)__________.
Earthquake
Volcanoes also exist under the water. Underwater eruptions called _______________ are 20 times more frequent than eruptions on land.
Submarine Eruptions
__________ are scientists who study volcanoes.
Volcanologists
Waves of energy are sent out from the _______, or beginning point of an earthquake.
Focus
The __________ scale measures the amount of destruction that an earthquake causes to manmade structures.
Mercalli
The __________ scale measures the magnitude, or strength, of the seismic waves of an earthquake.
Richter