Earth Science: Geology, Atmosphere, and Astronomy
Earth Science in the Chiba Entrance Science exam tests plate tectonics, rocks and the rock cycle, earthquakes and seismic waves, weather and climate, and basic astronomy. Strong answers connect a process to observable evidence and use scale correctly.
Core rules
- Earth's lithospheric plates move at centimeters per year; divergent boundaries create new crust, convergent boundaries can produce subduction and volcanoes, and transform boundaries produce strike-slip faults.
- Igneous rocks form from cooling magma or lava, sedimentary rocks from deposited and compacted material, and metamorphic rocks from heat and pressure.
- P-waves are longitudinal and travel faster than S-waves; S-waves cannot pass through liquids.
- Atmospheric pressure decreases with altitude; weather involves unequal heating, pressure gradients, and moisture.
- Earth's seasons result mainly from axial tilt, not from changing distance from the Sun.
Worked example
A seismic station records a P-wave at 8 km/s and an S-wave at 4 km/s. The S-wave arrives 20 s after the P-wave. Let d be the distance in kilometers. The travel times are d/8 and d/4, so d/4 - d/8 = 20. This simplifies to d/8 = 20, giving d = 160 km. The reasoning uses the arrival-time difference, not the absolute arrival time, and keeps both speeds in the same units.
Traps that cost marks
- Confusing the focus, where rupture begins, with the epicenter directly above it.
- Multiplying speed by the arrival-time difference when the difference is a time lag between two waves.
- Claiming S-waves pass through the outer core.
- Explaining seasons by distance rather than axial tilt.
- Ignoring map scale or vertical exaggeration in profiles.