Ch 2 N.D.

actualism

The principle that physical laws operating today operated in the past.

asthenosphere

The upper layer of the earth's mantle exhibiting plastic flow.

brittle

Prone to breaking or shattering easily under stress.

continental drift

The gradual movement of continents across the earth's surface.

convection

Heat transfer via the movement of fluids or semi-solids.

convergence zones

Regions where tectonic plates collide or move together.

core

The dense central region of the Earth.

crust

The outermost solid shell of a rocky planet.

divergence zones

Regions where tectonic plates move apart.

ductile

Capable of undergoing plastic deformation without breaking.

elastic

Capable of recovering original shape after stress removal.

epicenters

Points on the earth's surface directly above an earthquake focus.

fossils

Preserved remains or traces of ancient organisms.

Gondwanaland

An ancient southern supercontinent.

half-life

Time required for half of a radioactive isotope to decay.

hot spots

Volcanic regions fed by anomalously hot mantle plumes.

igneous rocks

Rocks formed from cooling magma or lava.

isostasy

Gravitational equilibrium between the Earth's crust and mantle.

Laurasia

An ancient northern supercontinent.

lava

Molten rock erupted onto the earth's surface.

lithosphere

The rigid outer shell of the Earth, including crust and upper mantle.

magma

Molten rock located beneath the earth's surface.

magnetic field

A region where magnetic forces act.

magnetic pole

Points where geomagnetic field lines are vertical.

magnetism

Physical phenomenon resulting from electric charges in motion.

mantle

The silicate rock layer between the crust and core.

mesosphere

The mantle region below the asthenosphere.

nuclear fission

Splitting of a heavy atomic nucleus releasing energy.

nuclear fusion

Combining light atomic nuclei to release energy.

Pangaea

The supercontinent that assembled all major landmasses.

Panthalassa

The vast global superocean surrounding Pangaea.

plates

Rigid slabs of lithosphere forming Earth's shell.

plate tectonics

Theory explaining Earth's crust dynamics via moving lithospheric plates.

plumes

Upwelling columns of hot mantle rock.

radioactive isotopes

Unstable atoms that decay by emitting radiation.

ridge

An underwater mountain system formed by spreading plates.

seafloor spreading

Process creating new oceanic crust at mid-ocean ridges.

spreading centers

Locations where new oceanic lithosphere forms.

strain

Material deformation resulting from applied stress.

stress

Force applied per unit area to a material.

subduction

Process where one tectonic plate descends beneath another.

tectonic cycle

Long-term cycle of crust creation and destruction.

tectonics

Study of Earth's crustal structure and deformations.

tidal friction

Frictional energy dissipation from ocean tides against the solid Earth.

topography

The arrangement of physical surface features.

transform faults

Strike-slip faults where plates slide horizontally past each other.

trenches

Deep, narrow depressions formed at subduction zones.

uniformitarianism

Principle that geological processes are uniform over time.

viscous

Having high resistance to fluid flow.

yield stress

Stress threshold where plastic deformation begins.