A volcanic system with current, measurable activity.ashFragments of volcanic rock less than 2 mm in diameter.
To take in.
The envelope of gases surrounding a planet, e.g., EarthÃ s atmosphere consists of approximately 80 percent nitrogen and 20 percent oxygen.
At typical levels.
A giant craterlike depression in EarthÃ s surface caused when a magma chamber collapses after a rapid, voluminous volcanic eruption.
A molecule consisting of one carbon atom and two oxygen atoms (CO2). Its gas is denser than air.continental crust
The part of EarthÃ s crust that includes and underlies the continents and continental shelves. The continental crust averages about 40 km thick.
A tectonic plate that includes continental crust, which is less dense than oceanic crust.
The outermost and thinnest of the solid EarthÃ s layers, which consists of rocky material that is less dense than the rocks of the mantle below.
The average mass per unit volume of a substance.
dome (lava dome)
A mound of viscous, gas-poor lava erupted from a volcanic vent. Because its viscosity prevents the lava from flowing far from the vent, it cools in a domed shape.
A sudden motion or trembling of EarthÃ s crust caused by the passage of seismic waves radiated from a fault along which sudden movement has occurred.
A series of earthquakes occurring around the same time, typically near a volcano.
The point on the surface of Earth directly above the subsurface source of an earthquake.
A steep cliff, either above or below sea level.
A rock fracture or fracture zone along which there has been movement.
A vent on EarthÃ s surface that emits volcanic gas.
Steam (water gas), carbon dioxide, sulfur dioxide, and other gases that are dissolved in magma. When magma erupts onto EarthÃ s surface, it releases these gases. Volcanic gas also can issue directly through fumaroles and soil.
The study of Earth, its history, its composition, its structure, and the dynamic processes that shape it.geophysicsThe study of EarthÃ s physical properties.
Heat sources under EarthÃ s surface.
A hot spring that can erupt water and steam. Geysers typically occur when geothermal processes keep fluids in a confined area of a fracture or vent at high temperature and under high pressure.
global positioning system (GPS)
A system of satellites, computers, and receivers that can determine the location (latitude and longitude) of a receiver on Earth.
All the water contained in the spaces within the subsurface.hot spotA fixed point on the EarthÃ s surface with long-lived volcanism.hydrogen sulfideH2S gas. It is toxic, flammable, and smells like rotten eggs.
Of or caused by the circulation of hot water due to thermal processes in EarthÃ s crust.
Hot water, steam, and other gases trapped in fractured or porous rocks underneath EarthÃ s surface.kilometer (km)A unit of length equal to 1,000 meters, or 0.62 miles.lavaMagma when it erupts on EarthÃ s surface.
Rivers of magma that travel over EarthÃ s surface during a volcanic eruption.
The outer layer of solid rock that includes the crust and uppermost mantle. This layer, up to 100 km thick, forms Earth's tectonic plates.
Molten or partially molten underground rock.magma chamberA reservoir of magma.
A measure of the total amount of energy released by an earthquake.
The layer within Earth that lies between the crust and the core.
A unit of length in the metric system equal to 3.28 feet.mud potA pool of hot water and fine sediment through which steam, water, or volcanic gas escape.
One of several large, interlocking, mobile pieces of EarthÃ s lithosphere.
Relatively level high ground.
Low energy electromagnetic radiation, with long wavelengths and low frequencies.
Any naturally formed aggregate of one or more minerals, such as granite, shale, or marble.
Relating to or caused by an earthquake or earth vibration.
An instrument that detects and records the vibrations of Earth.
The study of earthquakes and other seismic waves.
The compound silicon dioxide (SiO2). Silica is an important component of many rocks and minerals. It can be found in several forms, including quartz and opals.
The zone of convergence of two tectonic plates, one of which usually overrides the other.
A sudden sinking or gradual downward settling of EarthÃ s surface with little or no horizontal motion.tectonic plateOne of several large, mobile pieces of EarthÃ s lithosphere adjoining other plates along zones of seismic activity.
The process or result of raising a portion of EarthÃ s crust through tectonic mechanisms.ventAn opening such as a fissure, fracture, crack, or hole in EarthÃ s crust through which magma and gas escape.
Having a thick consistency somewhere between a solid and a liquid. The more viscous a material, the more resistant it is to flow.
A region of related volcanoes or volcanic activity.
A vent or fissure in the Earth's surface through which molten lava, ash, and gases are ejected. It is also the name for the structure, usually conical, formed by the materials ejected from the vent or fissure.
A scientist who studies volcanoes.