Descriptionary

seismograph a device that senses and records vibra­tions of the Earth.

shield volcano the largest type of volcano (such as those found in Hawaii) but the least explosive due to a low silica content.

skylight an opening in the roof of a lava tube.

solfatara a fumarole that emits sulfurous gases.

spatter cone a pile of basaltic material forming a cone over a fissure or vent.

stratovolcano a volcano that emits lava and ejects rock matter.

subduction zone the ridge where two tectonic plates meet and one overrides the other.

talus a slope comprised of broken rocks.

tephra collective term for all elastic material ejected in an eruption, from sand-sized particles to chunks of rock 200 feet wide.

tilt the slope of a volcano's flank as measured against itself in the past or against another reference point.

tiltmeter a vulcanist's tool for measuring the growth rate of a bulge in the side of a volcano.

tremor continuous seismic activity due to the flow of magma.

tsunami a massive ocean wave formed by an earth­quake or a volcanic eruption, or sometimes when an entire flank of a volcano collapses into the sea. A tsu­nami can travel from one side of an ocean to another.

tuff rock formed from volcanic activity.

tumulus a hardening sheath of cooling lava that forms over a hotter, flowing river of lava below.

vent any opening through which hot gas or molten materials escape.

volcanic pipe a large shaft of solidified magma, topped by a crater; a rich source of diamonds and other gems.

volcanic winter a drop in worldwide temperature due to volcanic activity, especially that which obscures part of the sky and the Sun's rays with volcanic ash.

volcanologist a scientist who studies volcanoes and volcanic activity. Also known as a vulcanist.

vulcanist see volcanologist.

Vulcanus the Roman god of fire.

wind and storms

Aeolus the Greek god of wind.

anemometer three-cupped device that rotates with the wind to measure its velocity.

backing wind a wind that gradually shifts coun­terclockwise through the compass; the opposite of a veering wind.

Beaufort scale a scale in which wind speeds are assigned the code numbers 0 to 12, corresponding to "calm" to "hurricane."

blustery National Weather Service's descriptive term for winds from 15 to 25 miles per hour; interchange­able with breezy and brisk.

breeze classification light—4 to 7 mph; moder­ate—13 to 18 mph; fresh—19 to 24 mph; strong—25 to 31 mph; gale—39 to 46 mph; strong gale—47 to 54 mph; storm wind—55 to 63 mph; violent storm wind—64 to 72 mph; hurricane—73 and up (mph = miles per hour).

breezy National Weather Service's descriptive term for winds from 15 to 25 miles (24-40 km) per hour. Also known as blustery and brisk.

brisk National Weather Service's descriptive term for winds from 15 to 25 miles (24-40 km) per hour. Also referred to as blustery and breezy.

cat's paw any slight breeze that lightly ripples the sea's surface.

chinook any warm dry wind descending the leeward slope of a mountain; known as a foehn in Europe.

chubasco a violent squall on the west coast of tropi­cal and subtropical North America.

condensation funnel a funnel cloud comprised of condensed water droplets.

cordonazo hurricane-borne wind blowing from the south on the west coast of Mexico.

Coriolis force force resulting from the Earth's rota­tion, which causes and deflection.

cyclone a massive rotating storm measuring hun­dreds or thousands of miles across, turning counter­clockwise above the equator and clockwise below, generally less violent than a hurricane.

derecho a very large and powerful windstorm spawned by a line of thunderstorms. Derechos usu­ally stretch for 250 miles (460 km) or more and are characterized by sustained winds from at least 58 miles per hour (92 km/hr) to an excess of 100 miles per hour (160 km/hr).

doldrums steamy equatorial regions with dead-calm winds and flat seas.

dust devil a rapidly whirling column of wind that sucks up dust and resembles a miniature tornado, seen over deserts.

dust-tube tornado see landspout.

elephant trunk tornado a long, sinuous tornado that stretches sideways across the sky and then touches down, resembling an elephant's trunk.

eolian pertaining to or caused by the wind.

etecians any winds that recur each year, or the recurring northerly summer winds over the eastern Mediterranean.

harmattan a dry, dusty wind of the west coast of Africa, blowing from the deserts.