Earth and Space: geology, hydrosphere, atmosphere, and astronomy
This domain covers Earth materials and processes, water and air systems, and astronomical cycles. Questions ask you to classify rocks, explain plate tectonics or the water cycle, interpret atmospheric phenomena, and distinguish rotation, revolution, seasons, and moon phases.
Geology
Igneous rock forms from cooling magma or lava; sedimentary rock forms from compacted and cemented sediments; metamorphic rock forms when existing rock is changed by heat and pressure. The rock cycle links these types through melting, cooling, weathering, erosion, deposition, and metamorphism. Plate tectonics explains earthquakes, volcanoes, mountain building, and sea-floor spreading at plate boundaries.
Hydrosphere and atmosphere
The water cycle includes evaporation, transpiration, condensation, precipitation, infiltration, and runoff. A watershed is an area draining into a common water body; erosion moves sediment, and deposition drops it. The atmosphere is mostly nitrogen and oxygen, with layers including the troposphere where weather occurs and the stratosphere containing the ozone layer. Greenhouse gases trap heat; ozone depletion is a different issue from global warming.
Astronomy
Earth rotates on its axis once about every 24 hours, causing day and night. Earth revolves around the Sun once a year. Seasons are caused by Earth's axial tilt, not by distance from the Sun. Moon phases depend on the relative positions of the Sun, Earth, and Moon; a solar eclipse occurs when the Moon blocks the Sun, and a lunar eclipse when Earth's shadow covers the Moon. Tides are mainly caused by the Moon's gravitational pull.
Worked example
A student claims summer occurs because Earth is closer to the Sun. The claim is wrong for the Northern Hemisphere: Earth is actually closest to the Sun in early January. Summer in the Northern Hemisphere occurs when the North Pole is tilted toward the Sun, so sunlight strikes more directly and days are longer. The reasoning separates revolution from axial tilt and shows why distance alone cannot explain opposite seasons in the two hemispheres.
Traps
- Saying seasons are caused by distance from the Sun.
- Confusing rotation with revolution.
- Mixing up solar and lunar eclipses.
- Treating the ozone hole and greenhouse effect as the same phenomenon.
- Forgetting that metamorphic rock forms from existing rock, not from magma.
- Confusing erosion with deposition.