Foundations of Earth and Space Science
This domain tests how Earth and space science is practiced: the nature of science, measurement and data, maps, and Earth as a system of interacting spheres. Expect items on experimental design, SI units, density, scale conversions, latitude and longitude, topographic maps, and the geosphere–hydrosphere–atmosphere–biosphere–cryosphere framework.
Core rules and concepts
- Experiments vs. observation. A controlled experiment manipulates one independent variable, holds the rest constant, and compares results to a control. Historical sciences (geology, astronomy) cannot manipulate their subject, so they rely on multiple converging lines of evidence, prediction, and testable mechanisms.
- Measurement. SI base units are the meter, kilogram, second, kelvin, mole, ampere, and candela. Density = mass ÷ volume (g/cm³ or kg/m³); water at 1.0 g/cm³ is the benchmark for floating and sinking.
- Coordinates. Lines of latitude run east–west and measure distance north or south of the equator (0°–90°); 1° of latitude is about 111 km everywhere. Lines of longitude converge at the poles, so 1° of longitude shrinks from about 111 km at the equator to zero at the poles.
- Topographic maps. Contour lines join points of equal elevation; the contour interval is constant across one map. Closely spaced contours mean a steep slope; hachured contours mark depressions; index contours are labeled with elevation.
- Systems. Matter and energy move among Earth's spheres, so a change in one (volcanic CO₂, deforestation, ice melt) propagates into the others.
Worked example
A map has a 20 m contour interval. Point A lies on the 340 m index contour, and point B lies on the 220 m contour 1.5 km away. Gradient = elevation change ÷ horizontal distance = (340 − 220) m ÷ 1500 m = 120 ÷ 1500 = 0.08, or 80 m/km (8%). Convert to a common unit before dividing; reporting "0.08 m/km" signals a missed conversion.
Traps that cost marks
- Reading the wrong contour label, or forgetting that hachures mean a depression rather than a hill.
- Swapping latitude and longitude, or assuming a degree of longitude is always 111 km.
- Leaving kilometers and meters mixed in a gradient or scale calculation.
- Calling a hypothesis a guess, or treating a single study as proof.