Praxis Earth and Space Sciences flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Moho discontinuity

Boundary between Earth's crust and mantle, identified by an abrupt increase in seismic wave velocity; depth averages about 35 km under continents and 5-10 km under oceans.

S-wave shadow zone

Region beyond about 103 degrees from an earthquake where no direct S waves arrive, because shear waves cannot travel through the liquid outer core.

Isostasy

Equilibrium condition in which crustal blocks float on the denser mantle; Airy model varies root thickness, Pratt model varies crustal density to balance mass.

Radiometric half-life

Time required for half of a radioactive parent isotope to decay; used with the decay equation to calculate ages of rocks and minerals.

Bowen's reaction series

Sequence describing crystallization order of silicate minerals from cooling magma, from olivine and Ca-plagioclase at high temperature to quartz and K-feldspar at low temperature.

Mohs hardness scale

Relative scale from 1 (talc) to 10 (diamond) ranking mineral resistance to scratching; used with streak and cleavage to identify unknown minerals.

Clastic sedimentary rock

Rock made of weathered fragments classified by grain size, such as conglomerate, sandstone, and shale; sorting and rounding reveal transport history.

Mass wasting

Downslope movement of rock and soil under gravity, classified by material and motion type, such as creep, slump, debris flow, and rockfall.

Thermohaline circulation

Global deep-ocean conveyor driven by differences in temperature and salinity, which control density; North Atlantic Deep Water formation is a key driver.

Ekman transport

Net movement of surface water about 90 degrees to the right of the wind in the Northern Hemisphere, caused by Coriolis deflection, driving coastal upwelling.

Spring tide

Unusually large tidal range occurring near new and full moon, when solar and lunar tidal forces align and reinforce each other.

Darcy's law

Groundwater flow rate equals hydraulic conductivity times cross-sectional area times hydraulic gradient: Q = K A (dh/dL); describes flow through porous media.

Environmental lapse rate

Actual rate at which air temperature decreases with altitude in the troposphere, averaging about 6.5 degrees C per km; compared with adiabatic rates to assess stability.

Coriolis effect

Apparent deflection of moving air or water caused by Earth's rotation; deflects to the right in the Northern Hemisphere and left in the Southern Hemisphere.

Cold front

Boundary where cold air advances under warm air, producing steep uplift, narrow bands of heavy precipitation, and rapid temperature drops after passage.

Hurricane formation conditions

Requires warm ocean water above about 26 degrees C, high humidity, low wind shear, and Coriolis effect to organize rotating thunderstorms into a tropical cyclone.

Kepler's third law

Square of orbital period is proportional to cube of semi-major axis; with period in years and axis in AU, P squared equals a cubed.

Hertzsprung-Russell diagram

Graph plotting stellar luminosity against temperature or spectral class; main sequence, giants, supergiants, and white dwarfs occupy distinct regions.

Hubble's law

Recession velocity of a galaxy is proportional to its distance, v = H0 d; evidence that the universe is expanding.

Solar nebula theory

Model in which a collapsing cloud of gas and dust forms a rotating disk, accretes planetesimals, and produces terrestrial planets inside the frost line and giants outside.

Synchronous rotation

Condition in which a body's rotation period equals its orbital period, so the same hemisphere always faces its partner; the Moon rotates this way.

Albedo

Fraction of incoming solar radiation reflected by a surface or planet; Earth's average is about 0.30, with ice and clouds having high values.

Milankovitch cycles

Variations in Earth's eccentricity, axial tilt, and precession that change solar insolation distribution and pace glacial-interglacial climate cycles.

Geodynamo

Process in which convection and rotation of liquid iron in the outer core generate Earth's magnetic field, which forms the magnetosphere.

ENSO

El Nino-Southern Oscillation, a coupled ocean-atmosphere pattern in the tropical Pacific that shifts global precipitation and temperature; La Nina is its cool phase.

Dependent variable

The measured outcome in an experiment that responds to changes in the independent variable; plotted on the vertical axis of a graph.

Accuracy versus precision

Accuracy is closeness of a measurement to the true value; precision is closeness of repeated measurements to each other, reflecting instrument consistency.

Contour lines

Lines on a map connecting points of equal elevation; spacing indicates slope steepness, and closed loops mark hills or depressions.

Correlation versus causation

A statistical association between variables does not prove one causes the other; confounding variables or coincidence may explain the relationship.

5E instructional model

Lesson framework with Engage, Explore, Explain, Elaborate, and Evaluate phases; supports inquiry-based science learning and formative assessment.

Formative assessment

Ongoing checks of student understanding during instruction, used to adjust teaching; contrasted with summative assessment at the end of a unit.

Percent error

Measure of experimental accuracy calculated as the absolute difference between measured and accepted values divided by the accepted value, multiplied by 100.