moment magnitude scale introduced in 1979, a scale that more accurately measures the energy released by earthquakes stronger than 7 on the Rich- ter scale, with the ability to measure more accurately from distances greater than 350 miles (600 km).
plate tectonics the interaction and subsequent effects of the Earth's continental plates colliding and scraping up against each other, as seen most notably in the San Andreas Fault in California.
precursor a geological event that immediately precedes an earthquake, including a change in seismic velocities, and groundwater levels and a tilting of ground surface.
primary wave the fastest traveling earthquake wave, also known as a P-wave or compressional wave. It is a pressure wave that compresses and decompresses the Earth as it travels out from an epicenter. P-waves are faster moving but less destructive than S-waves. The roar often heard at the start of an earthquake is actually a burst of P-waves reaching the Earth's surface and agitating air molecules.
P-wave see primary wave.
Richter scale a scale determining the magnitude of an earthquake as recorded by seismographs. Due to the logarithmic basis of the scale, each whole number increase in magnitude represents a 10-fold increase in magnitude. For example, an earthquake measuring 6.7 on the Richter scale would be considered 10 times worse than one measuring 5.7.
right-lateral fault faulted ground that moves or has moved to the right as you face it.
sand blow a small, volcano-like formation made by the explosion of liquefied soil during an earthquake, also known as sand volcano.
seaquake see submarine earthquake.
earthquakes 125
secondary wave an earthquake wave, also known as an S-wave or shake wave, slower than a P-wavebut more powerful. An S-wave causes the Earth to shake back and forth as it travels out from an epicenter; however, it cannot move through water.
seismic referring to earthquake activity.
seismic prospecting a technique of determining the nature of an underground rock structure by setting off explosive charges and measuring the time it takes the shock waves to travel varying paths; a seismic profile is attained this way.
seismic wave a wave of movement that travels through the Earth.
seismograph an instrument that records vibrations of the Earth.
seismology the study of earthquakes and other vibrations of the Earth.
seismometer an electronic instrument that measures and records ground motion. Also known as a seismograph.
subduction zone any area where one tectonic plate descends and forces its way beneath another tectonic plate, a source of earthquake and volcanic activity.
submarine earthquake an earthquake originating beneath the seafloor.
S-wave see secondary wave.
temblor a tremor or earthquake.
tremor a small earthquake or vibration, often occurring before or after a major earthquake.
tsunami the Japanese term for harbor wave, formerly and erroneously known as a tidal wave. A tsunami is actually any one of what is usually a series of waves that may reach a height of 100 feet (30.5 m) and can cross an entire ocean at speeds up to 600 miles per hour (966 km/h), usually caused by an earthquake, underwater landslide, or collapse of an onshore landmass, such as a volcano, into a large body of water.
tsunami detection buoy a surface buoy connected to an underwater pressure sensor that can detect tsunamis and relay alerts via satellite.
tsunami warning network a series of tsunami detection buoys anchored throughout the ocean, capable of sending alerts via satellite.
FIELDS, MEADOWS, AND MARSHES
bracken any moist area with a heavy growth of a fern by the same name.
brake an area of thick brush.
everglade a marshland with tall stands of grass.
heath a large field or plain covered with small shrubs, such as heather.
moor a frequently elevated field covered with heather, bracken, and marshy areas.
pampas the grassy plains in South America lying from the Andes to the Atlantic Ocean. The equivalent of the North American prairie.
plain a large area of mostly treeless grassland.
prairie grassy plains of midwest North America.
rush any of various marsh plants or grasses having hollow stems.
savanna a tropical or subtropical grassland, sometimes having scattered trees.
sedge a grasslike marsh plant.
steppes grasslands of Eurasia.
tundra treeless plains with marshy areas, in Siberia and arctic North America.
tussock a thick tuft of grass.
veld elevated, treeless grassland of South Africa.
flowers and plants
achene a small, hard, dry, one-seeded fruit that doesn't split open or yawn when ripe, typically found with buttercups and dandelions.
aerial rootlets small rootlike branches growing out of the stems of some climbing vines.
ananthous flowerless.
annual living and growing only one year or season.
anther at the top of a stamen, the tiny organ that secretes and discharges pollen.
armed bearing prickles, spines, or thorns.
aromatic spicy- or sweet-smelling.
axis the main stem or center around which plant parts or branches grow.
beard a group of bristles or hairs on a plant.
biennial a plant with the cycle of two years, producing leaves the first year, and fruit or flowers the second.
blade the flat, green expanse portion of a leaf, as opposed to the stalk.
bloom a white, powdery coating found on some fruits, such as plums, and the leaves and stems of various plants.
bract a small leaf beneath a flower or on the stalk of a flower cluster.
bud a leafy stem or flower unopened and undeveloped.
bulb an underground root or stem with fleshy scales and a food store for the undeveloped plant within.
calyx a collective term for the sepals of a flower; the leaflike green segments forming the outer circle in a flower.
catkin small flower cluster, drooping and resembling a kitten's tail; commonly found on willow and birch trees.
chaff husks of grain separated from the seed.
chlorophyll the green pigment found in plants.
claw the stalklike base of a petal.
corm a scaleless bulb or stem base.
corolla the collective term for the petals of a flower, separate or joined.
corymb a flat-topped flower cluster in which the outer flowers open first.
cyme a flat-topped flower cluster in which the middle or central flowers open first.
disk flower the tubular flowers that project from the center of the heads of daisies, sunflowers, and asters.
downy a coating of short, fine, soft hairs.
drupe any fruit, such as a peach, plum, or cherry, that has a hard pit or stone.