MTLE Earth and Space Science (Grades 9-12) flashcards

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

Earth's mean radius

Approximately 6,371 km. The crust is thin (5-70 km), the mantle extends to about 2,900 km depth, and the liquid outer core surrounds a solid inner core.

P-waves versus S-waves

P-waves are compressional and travel through solids and fluids, arriving first. S-waves are shear waves that travel only through solids, creating a shadow zone beyond 103 degrees.

Convergent plate boundary

A boundary where plates move toward each other, producing subduction zones with deep earthquakes and volcanic arcs, or continental collision with mountain building.

Seafloor magnetic stripes

Symmetrical bands of alternating magnetic polarity on the ocean floor record reversals of Earth's field as new crust forms at mid-ocean ridges, supporting seafloor spreading.

Law of superposition

In undisturbed sedimentary sequences, older layers lie below younger ones. This relative dating principle underlies stratigraphic correlation and the geologic column.

Radiometric dating

Age determination from the ratio of parent to daughter isotopes using a known half-life. Carbon-14 dates organic remains to about 50,000 years; uranium-lead dates ancient rocks.

Rock cycle

The continuous transformation among igneous, sedimentary, and metamorphic rocks through melting, crystallization, weathering, erosion, deposition, lithification, and metamorphism under heat and pressure.

Milankovitch cycles

Variations in Earth's orbital eccentricity, axial obliquity, and precession that alter solar insolation and pace glacial-interglacial climate cycles over tens of thousands of years.

Axial tilt and seasons

Earth's 23.44-degree tilt causes seasonal changes by varying solar angle and daylight length. Distance from the Sun is not the cause of seasons.

Troposphere

The lowest atmospheric layer, where temperature decreases with altitude at about 6.5 degrees Celsius per kilometer and where most weather and water vapor occur.

Coriolis effect

The apparent deflection of moving air or water caused by Earth's rotation: rightward in the Northern Hemisphere, leftward in the Southern, zero at the equator.

Relative humidity

The ratio of water vapor actually present to the maximum the air could hold at that temperature, expressed as a percentage. Cooling to the dew point causes saturation.

Thermohaline circulation

Deep ocean circulation driven by differences in temperature and salinity, which control density. It transports heat globally and is distinct from wind-driven surface currents.

Watershed

The land area draining into a common river or lake, bounded by topographic divides. Precipitation within it flows to a shared outlet.

Kepler's third law

The square of an orbital period is proportional to the cube of the semi-major axis, P squared equals a cubed when P is in years and a in astronomical units.

Nebular hypothesis

The solar system formed from a collapsing, rotating cloud of gas and dust that flattened into a disk; inner planets are rocky and outer planets icy and gaseous.

Hertzsprung-Russell diagram

A plot of stellar luminosity against temperature or spectral class. Main-sequence stars, giants, supergiants, and white dwarfs occupy distinct regions of the diagram.

Stellar life cycle

Stars fuse hydrogen on the main sequence, expand to giants, then shed layers as white dwarfs or explode as supernovae, leaving neutron stars or black holes.

Hubble's law

Galaxies recede at speeds proportional to distance, v equals H-zero times d. This relationship supports an expanding universe originating in the Big Bang.

Cosmic microwave background

Relic radiation from about 380,000 years after the Big Bang, now cooled to roughly 2.7 kelvin, providing evidence for the hot early universe.

Lunar phases

The changing illuminated fraction of the Moon as it orbits Earth, completing a synodic cycle of about 29.5 days from new moon through full moon and back.

Solar and lunar eclipses

A solar eclipse occurs at new moon when the Moon blocks the Sun; a lunar eclipse occurs at full moon when Earth's shadow covers the Moon. Alignment must be near orbital nodes.

Earth's energy budget

Incoming shortwave solar radiation balances reflected shortwave light plus outgoing longwave infrared. Greenhouse gases absorb and re-emit infrared, warming the surface.

Electromagnetic spectrum

Ordered by increasing frequency: radio, microwave, infrared, visible, ultraviolet, X-ray, gamma. Wavelength and frequency are inversely related through the speed of light.

Doppler effect

A shift in observed wavelength caused by relative motion. Approaching sources appear blueshifted and receding sources redshifted, revealing stellar and galactic motion.

Emission and absorption spectra

Bright lines at specific wavelengths identify elements in emission; dark lines against a continuum indicate absorption. Each element has a unique spectral signature.

Newton's law of gravitation

The gravitational force between masses equals G times m-one times m-two divided by the square of their separation, governing orbits, tides, and weight.

Mohs hardness scale

A relative scale from 1 (talc) to 10 (diamond) ranking mineral resistance to scratching. Hardness, cleavage, luster, and streak help identify minerals.

Plate motion evidence

GPS measurements, matching continental margins and fossils, paleomagnetic stripes, and seafloor age patterns confirm plates move a few centimeters per year.

Earthquake magnitude

A logarithmic measure of energy released at an earthquake source. Each whole-number increase represents roughly thirty times more energy than the previous level.

Igneous rock formation

Crystallization of magma or lava. Slow cooling underground produces coarse-grained intrusive rock; rapid surface cooling produces fine-grained extrusive rock.

Albedo

The fraction of incoming solar radiation reflected by a surface. Earth averages about 0.30; snow and ice reflect far more than oceans or forests.