Natural Disasters Ch. 2

actualism

using the actual process operating on Earth today to interpret the past; not inventing unrecognized processes to explain the past

asthenoshere

the layer of the Earth below the lithosphere in which isostatic adjustments take place. The rocks here deform readily & flow slowly

brittle

behavior of material whereby stress causes abrupt fracture

continental drift

the movement of continents across the face of Earth, including their splitting apart & recombing into new continents

convection

process of heat transfer whereby hotter air, water, or rock rises upward due to its lower density while cooler material above sinks because of its higher density

convergence zones

a linear area where pates collide and move closer together. This is a zone of earthquakes, volcanoes, mountain ranges, and deep-ocean trenches

ductile

behavior of material whereby stress causes permanent flow or strain

elastic

behavior of material whereby stress causes deformation that is recoverable; when stress stops, the material returns to its original state

epicenters

the point on the surface of the Earth directly above a fault movement (i.e., earthquake location)

fossils

evidence of former life, including bones, shells, teeth, leaves, and footprints

Gondwanaland

a southern super-continent that included South America, Africa, Antarctica, Australia, New Zealand, and India during Jurassic time

half-life

the length of time needed for half of a radioactive sample to lose its radioactivity via decay

hot spots

a region on Earth’s surface that has abundant volcanism fed by underlying mantle rock that is anomalously hot. They may be on, close to, or far from tectonic plates

igneous rocks

rock formed by the solidification (crystallization) of magma

isostasy

the condition of flotational equilibrium wherein the Earth’s crust floats upward or downward as loads are removed or added

Laurasia

a northern supercontinent that included most of North America, Greenland, Europe, and Asia (excluding India) from about 180 to 75 million years ago

lithosphere

the outer rigid shell of the Earth that lies above the asthenosphere and below the atmosphere and hydrosphere

magma

molten or liquid rock material. It crystallizes (solidifies) on the Earth’s surface as volcanic rock and at depth as plutonic rock

magnetic field

a region where magnetic forces affect any magnetized bodies or electric currents. Earth is surrounded by this

magnetic pole

the point where Earth’s magnetic field flows back into the ground. Currently, this point is near the North Pole

magnetism

a group of physical phenomena associated with moving electricity

mantle

the largest zone of the Earth, comprising 83% by volume and 67% by mass

mesosphere

1.the mantle from the base of the asthenosphere to the top of the core 2.the atmosphere layer above the stratosphere and below the thermosphere

nuclear fission

splitting the nucleus of an atom, with the resultant release of energy, neitrons, and large daughter products

nuclear fusion

combining smaller atoms to make larger atoms, with a resultant release of energy

Pangaea

a supercontinent that existed during Late Paleozoic time when all the continents were unified into a single landmass

Panthalassa

a massive, single ocean that occupied 60% of Earth’s surface in Late Paleozoic time

plates

a piece of lithosphere that moves atop the asthenosphere. There are a dozen large plates and many smaller ones

plate tectonics

the description of the movements of plates and the effects of plate formation, collision, subduction, and slide-past

plumes

an upward-rising column, such as magma, smoke, or cloud. From the Latin word meaning “feather”

radioactive isotopes

unstable element containing excess subatomic particles that are emitted to achieve a smaller, stable atom

ridge

a volcanic mountain range that lies along the spreading centers on the floors of the oceans

seafloor spreading

where tectonic plates pull apart, magma wells up and solidifies to create volcanic mountains, which in turn are pulled apart as new ocean floor

spreading centers

the site where plates pull apart and magma flows upward to fill the gap and then solidifies as new lithosphere/ocean floor

strain

a change in the form or size of a body due to external forces

stress

external forces acting on masses or along surfaces; forces include shear, tension, and compression

subduction

the process of one lithosphere plate descending beneath another one

tectonic cycle

new lithosphere forms at oceanic volcanic ridges, the lithospheric plates spread apart to open ocean basins, and then the oceanic plates are reabsorbed into the mantle at subduction zones

tectonics

the deformation and movement within the Earth’s outer layers

tidal friction

gravitational attraction between Earth, Moon, and Sun stretches the solid mass of the Earth and converts some energy from Earth’s rotation into heat

topography

the shape of Earth’s surface both above and below sea level

transform faults

a strike-slip fault that connects the ends of two offset segments of plate edges, such as spreading centers or subduction zones

trenches

the elongate and narrow troughs where ocean water can be more than twice as deep as usual. They mark the down-going edges of subducting plates

uniformitarianism

the concept that the same law and processes operating on and within Earth throughout geologic time are the same laws and processes operating today

viscous

ease of flow. The more vicious a substance, the less readily it flows

yield stress

the stress difference at which permanent deformation first occurs