Earth and Space Science
What you must understand
Earth and space science on this exam centers on patterns you can observe and explain: the rock cycle, plate tectonics, weathering and erosion, the water cycle, Earth's rotation and revolution, and the Sun-Earth-Moon system. Know that Earth's rotation (spinning on its axis, about 24 hours) causes day and night, while its revolution (one orbit around the Sun, about 365 days) plus a steady axial tilt causes the seasons. Know the phases of the Moon as the changing portion of the sunlit half we see from Earth, and that eclipses require near-perfect alignment of Sun, Earth, and Moon.
Traps to watch for
- Seasons are not caused by distance from the Sun. Earth is actually slightly closer to the Sun during Northern Hemisphere winter. The tilt is the cause.
- Weathering versus erosion. Weathering breaks rock down in place; erosion moves the pieces. A question about a rock cracking from ice is weathering; a question about sediment piling up downstream is erosion and deposition.
- Moon phases versus eclipses. Phases happen every month; eclipses are rare because the Moon's orbit is tilted relative to Earth's orbit.
- Rock types. Igneous forms from cooled magma or lava, sedimentary from compacted and cemented sediments, metamorphic from heat and pressure. A rock can pass through all three.
Rule of thumb
For any Earth event, ask: What is moving or changing, and what energy drives it? Most answers trace back to sunlight, Earth's internal heat, or gravity.
Worked example
A student finds layered rock with a fish fossil. Which rock type is it, and what does the fossil tell you? Layered rock with fossils is sedimentary. The fossil shows the area was once underwater and that the organism was buried in sediment that later hardened.