Dacite is a type of volcanic rock that is light-colored and rich in silica (63 to 68 percent).

 debris avalanche
A debris avalanche is a sudden rock/soil/debris slide and flows with great speed from a volcano.

 debris flow
A debris flow (also called a mudflow or lahar) is a moving mixture of rock, water, and other debris.


Decibels (abbreviated dB) are the unit of measuring the loudness (or intensity) of sounds. 0 dB is the faintest audible sound. The decibel scale is logarithmic. Blue whale calls are up to 188 dB; this is the loudest animal sound, and is painful to the human ear. Volcano eruptions are one of the loudest sounds on Earth and
are over 272 dB.

A degree is a measure of temperature or angle.

A diatreme is a volcanic vent or pipe that is formed by gas-charged magma.


A dike is a sheet-like intrusion of magma (molten rock) that froces its way through a layer of fractured rock. The magma flows through cracks in the rock and later cools and solidifies into a sheet of igneous rock.

A lava dome is a dome-shaped mound that is formed around a vent by viscous lava.


 dormant volcano

A dormant volcano is a volcano that is not active now, but may erupt in the future.

Volcanic dust is a solidified lava that is tiny particles. It is ejected from volcanos during an eruption.


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