NY Regents Earth Science cheat sheet

Density = mass ÷ volume; water's density is 1.0 g/mL at 4 °C, and ice is less dense because its crystal structure holds molecules farther apart.

Specific heat of liquid water is about 4.18 J/(g·°C), among the highest of common substances, so oceans heat and cool slowly and moderate coastal climates.

Latent heat: melting ice absorbs about 334 J/g and boiling water absorbs about 2260 J/g, with no temperature change during the phase change.

Energy moves by radiation (no medium needed), conduction (solids, molecule-to-molecule contact), and convection (fluids, density-driven circulation).

Earth's external energy source is the Sun; internal energy comes from radioactive decay and residual heat of formation, driving convection in the mantle.

Density of a material generally increases when cooled and decreases when heated, except water between 0 °C and 4 °C, which contracts on warming.

Dynamic equilibrium: a system is balanced when inputs equal outputs; a disturbance causes change until a new balance is reached.

Phase changes: solid to liquid is melting, liquid to gas is evaporation or boiling, gas to liquid is condensation, and solid directly to gas is sublimation.

Earth's layers by composition: crust (continental granite-rich, oceanic basalt-rich), mantle (peridotite), and core (iron-nickel).

Layers by physical state: lithosphere (rigid crust plus uppermost mantle), asthenosphere (plastic, partially molten, flows), mesosphere, outer core (liquid), inner core (solid).

Average continental crust is about 35 km thick and granitic; oceanic crust is about 5-10 km thick and basaltic, and oceanic crust is denser.

The Moho is the boundary between crust and mantle, detected by an abrupt increase in seismic wave velocity.

P-waves are compressional, travel through solids, liquids, and gases, and are faster; S-waves are shear waves that cannot pass through liquids.

The S-wave shadow zone (about 103°-143° from the epicenter) proves the outer core is liquid; the P-wave shadow zone results from refraction at the core boundary.

Temperature and pressure increase with depth; the geothermal gradient averages about 25 °C per km in the crust, and the core is roughly 5000-6000 °C.

Earth's magnetic field is generated by convection of liquid iron in the outer core, and magnetic reversals recorded in seafloor rock support plate motion.

Evidence for continental drift: matching coastlines, fossil correlations, rock-type and mountain-belt matches, and paleoclimate indicators such as glacial striations.

Seafloor spreading evidence: magnetic stripe symmetry across mid-ocean ridges, youngest seafloor at ridges, and age increasing away from ridges.

Divergent boundary: plates move apart, forming mid-ocean ridges and rift valleys, with shallow earthquakes and basaltic volcanism.

Convergent boundary: plates collide; oceanic-continental gives subduction, trenches, and volcanic arcs; continental-continental gives folded mountains; oceanic-oceanic gives island arcs.

Transform boundary: plates slide past each other, producing shallow earthquakes but little or no volcanism.

Hot spots form volcanic chains such as Hawaii; the bend in the chain records a change in plate motion direction.

Relative dating principles: superposition, original horizontality, lateral continuity, cross-cutting relationships, and inclusions.

Absolute dating uses radioactive decay; the half-life of carbon-14 is about 5730 years, useful only for materials younger than about 50,000 years.

The geologic time scale is divided by major extinction and evolutionary events; the Precambrian covers about 88% of Earth history, and the Phanerozoic includes Paleozoic, Mesozoic, and Cenozoic eras.

Mineral properties used for identification: hardness (Mohs scale 1-10), cleavage or fracture, luster, streak, color, and crystal form.

Silicate minerals dominate the crust; quartz is hardest of common minerals (7) with no cleavage, calcite has rhombohedral cleavage and fizzes in dilute acid.

Igneous rocks are classified by texture (intrusive coarse-grained, extrusive fine-grained) and composition (felsic to mafic); granite is felsic intrusive, basalt is mafic extrusive.

Sedimentary rocks form by compaction and cementation of sediments or by chemical precipitation; they are the only rock type that can contain fossils.

Metamorphic rocks form from heat and pressure; foliation, banding, and recrystallization are key features, as in gneiss and schist.

The rock cycle links igneous, sedimentary, and metamorphic rocks through melting, weathering, erosion, deposition, and metamorphism.

Weathering breaks rock in place (physical: frost wedging, abrasion; chemical: oxidation, hydrolysis, carbonation); erosion transports the products.

Stream erosion and deposition follow a gradient: fast water erodes and carries larger sediment, slow water deposits larger particles first, and sorted, rounded particles indicate water transport.

Mass movement types: creep, slump, mudflow, and landslide; steep slopes and water-saturated soil increase risk.

Atmospheric composition: about 78% nitrogen, 21% oxygen, 0.9% argon, and variable water vapor and carbon dioxide.

Temperature decreases with altitude in the troposphere (lapse rate about 6.5 °C/km), increases in the stratosphere due to ozone absorption, and decreases again in the mesosphere.

Air pressure decreases with altitude; wind blows from high pressure to low pressure, deflected by the Coriolis effect (right in the Northern Hemisphere).

Relative humidity is the ratio of actual water vapor to the maximum possible at that temperature; warm air holds more water vapor.

Cloud formation requires cooling of moist air to the dew point plus condensation nuclei; cumulonimbus clouds produce thunderstorms and hail.

Weather fronts: cold fronts bring short, intense precipitation and rapid temperature drops; warm fronts bring gradual, prolonged precipitation.

High pressure generally means clear, fair weather; low pressure means clouds and precipitation.

Climate is long-term average weather; factors include latitude, altitude, proximity to water, ocean currents, and prevailing winds.

Greenhouse gases absorb outgoing infrared radiation; the greenhouse effect warms Earth's surface and lower atmosphere.

Water cycle processes: evaporation, transpiration, condensation, precipitation, runoff, infiltration, and groundwater flow.

Porosity is the percentage of pore space in a material; permeability is the ability of a material to transmit water; well-sorted gravel has high porosity and high permeability.

The water table is the upper surface of the saturated zone; groundwater flows from higher to lower water table elevations.

Aquifer types: unconfined (open to the surface) and confined (between impermeable layers); a confined aquifer under pressure can produce an artesian well.

Ocean salinity averages about 35 parts per thousand; salinity is affected by evaporation, precipitation, and freshwater inflow.

Surface ocean currents are driven by wind and deflected by the Coriolis effect; the Gulf Stream carries warm water northward.

Density-driven deep ocean circulation is caused by differences in temperature and salinity (thermohaline circulation).

Tides result from gravitational pull of the Moon and Sun; spring tides occur at new and full moon, neap tides at quarter moons.

Watersheds divide drainage; runoff carries sediment and pollutants downstream, and impermeable surfaces increase runoff and flooding.

Earth's rotation on its axis (about once per 24 hours) causes day and night and the apparent motion of stars; revolution around the Sun (about 365.25 days) causes seasons.

Seasons result from the 23.5° tilt of Earth's axis, not from distance from the Sun; solstices and equinoxes mark the extremes and midpoints.

The Moon's phases result from the changing angle between Earth, Moon, and Sun; a full cycle takes about 29.5 days.

Solar eclipses occur at new moon when the Moon passes between Earth and Sun; lunar eclipses occur at full moon when Earth's shadow falls on the Moon.

Gravity governs orbits; Kepler's laws state that orbits are ellipses, planets sweep equal areas in equal times, and the square of the period is proportional to the cube of the semi-major axis.

The solar system formed from a rotating nebula of gas and dust; inner planets are rocky and dense, outer planets are large and low-density.

The Sun's energy comes from nuclear fusion of hydrogen into helium in its core; the Sun is a middle-aged main-sequence star.

The universe is expanding; the Big Bang occurred about 13.8 billion years ago, and redshift of distant galaxies supports expansion.

Stars are classified by temperature and luminosity on the Hertzsprung-Russell diagram; the main sequence runs from hot, bright to cool, dim.

A controlled experiment changes one independent variable while holding all other variables constant, and measures the dependent variable.

A hypothesis is a testable prediction; a theory is a well-supported explanation; a law describes a consistent relationship.

Metric units: length in meters, mass in grams, volume in liters or cubic centimeters, temperature in degrees Celsius, and density in g/cm³.

Scientific notation expresses numbers as a coefficient times a power of ten; 0.0045 = 4.5 × 10⁻³.

Percent error = |measured − accepted| ÷ accepted × 100%; percent deviation compares a measurement to an accepted value.

Significant figures reflect measurement precision; addition uses decimal places, multiplication and division use significant digits.

Graphing: place the independent variable on the x-axis and the dependent variable on the y-axis, label units, and use a best-fit line to show trends.

Interpolation estimates values between data points; extrapolation estimates beyond the data and is less reliable.

A scale and a legend are required on maps and graphs; gradients are calculated as change in field value divided by change in distance.

Use the ESRT (Earth Science Reference Tables) for density, mineral properties, rock classification, and the geologic time scale; know where each chart is located.

Measure liquid volume in a graduated cylinder at eye level, reading the bottom of the meniscus.

Use a triple-beam balance for mass; zero the balance before use, and record to the nearest 0.1 g.

Measure temperature with a thermometer fully immersed in the sample, wait for equilibrium, and read at eye level.

Use a stream table to model erosion and deposition; observe how gradient and discharge affect sediment transport.

Determine density by measuring mass and volume separately, then divide; use water displacement for irregular solids.

Identify minerals by testing hardness, streak, cleavage, and reaction with acid; record observations, not conclusions, in data tables.

Plot data on a graph with labeled axes and units, draw a best-fit line, and use the slope to calculate the rate of change.

Safety: wear goggles when using chemicals or heating, never taste samples, and report spills immediately.