Terms in this set (32)
a weak spot in the crust where molten material, or magma, comes to the surface
a molten mixture of rock-forming substances, gases, and water from the mantle
When magma reaches the surface, it is called lava
Ring of Fire
One major volcanic belt is the Ring of Fire, formed by the many volcanoes that rim the Pacific Ocean.
The resulting volcanoes create a string of islands called an island arc. The curve of an island arc echoes the curve of its deep-ocean trench
A hot spot is an area where material from deep within the mantle rises and then melts, forming magma.
a substance that cannot be broken down into other substances. Carbon, hydrogen, and oxygen are examples of elements
a substance made of two or more elements that have been chemically combined.
any characteristic of a substance that can be observed or measured without changing the composition of the substance
any property that produces a change in the composition of matter.
The physical property of liquids called viscosity is the resistance of a liquid to flowing
Magma is a complex mixture, but its major ingredient is silica. The compound silica is made up of particles of the elements oxygen and silicon.
is fast-moving, hot lava that has low viscosity. The surface of a lava flow formed from pahoehoe looks like a solid mass of wrinkles, billows, and ropelike coils
ava that is cooler and slower-moving is called aa Aa has higher viscosity than pahoehoe. When aa hardens, it forms a rough surface consisting of jagged lava chunks
Beneath a volcano, magma collects in a pocket called a magma chamber
he magma moves upward through a pipe, a long tube in the ground that connects the magma chamber to Earth's surface.
Molten rock and gas leave the volcano through an opening called a vent
is the area covered by lava as it pours out of a vent.
a bowl-shaped area that may form at the top of a volcano around the central vent.
occurs when an explosive eruption hurls out a mixture of hot gases, ash, cinders, and bombs.
Scientists expect a dormant volcano to awaken in the future and become active
An extinct, or dead, volcano is unlikely to erupt again.
Such lava flows gradually build a wide, gently sloping mountain called a shield volcano. Shield volcanoes rising from a hot spot on the ocean floor created the Hawaiian Islands.
f a volcano's lava has high viscosity, it may produce ash, cinders, and bombs. These materials build up around the vent in a steep, cone-shaped hill or small mountain called a cinder cone.
are tall, cone-shaped mountains in which layers of lava alternate with layers of ash
The huge hole left by the collapse of a volcanic mountain is called a caldera. The hole is filled with the pieces of the volcano that have fallen inward, as well as some lava and ash.
A volcanic neck forms when magma hardens in a volcano's pipe.
Magma that forces itself across rock layers hardens into a dike. Sometimes, a dike can be seen slanting through bedrock along a highway cut.
When magma squeezes between horizontal layers of rock, it forms a sill
a mass of rock formed when a large body of magma cools inside the crust
The word geothermal comes from the Greek geo meaning "Earth" and therme meaning "heat." In geothermal activity magma a few kilometers beneath Earth's surface heats underground water.
a fountain of water and steam that erupts from the ground.
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