12.3 Earth, Space, and Environmental Systems
Key Takeaways
- Earth and space science is a smaller but important GED Science domain, centered on systems, interactions, resources, hazards, atmosphere, oceans, geology, and space.
- GED Earth science questions usually test reasoning with a passage, graph, map, model, or data table rather than isolated vocabulary.
- Earth systems interact: changes in the atmosphere, hydrosphere, geosphere, and biosphere can affect one another.
- Environmental questions often connect natural resources, renewable and nonrenewable energy, sustainability, pollution, and ecosystem effects.
- Space science questions commonly use models of the solar system, moon phases, eclipses, tides, stars, galaxies, or evidence about Earth's age.
Earth and Space as Test Contexts
The GED Science assessment guide places Earth and space science beside life science and physical science. Earth and space topics are not just facts about rocks or planets. They are contexts for reasoning from evidence, reading models, comparing data, and judging claims about natural systems.
You should be broadly familiar with the main ideas, but you do not need college-level detail. A GED item might provide a diagram of tectonic plates, a table of hurricane data, a map of ocean currents, a model of the moon's orbit, or a passage about renewable energy. Your job is to use the stimulus to answer the question accurately.
Earth-System Map
| System | What it includes | GED-style connection |
|---|---|---|
| Atmosphere | Air, gases, weather, climate | Greenhouse gases, storms, pressure, wind |
| Hydrosphere | Oceans, rivers, groundwater, ice | Currents, flooding, erosion, water quality |
| Geosphere | Rocks, soil, landforms, plates | Earthquakes, volcanoes, weathering, fossils |
| Biosphere | Living organisms and ecosystems | Food webs, habitat change, resource use |
Interactions and Cycles
Earth systems affect one another. Heavy rain in the atmosphere can cause flooding in the hydrosphere, which erodes soil in the geosphere and damages habitats in the biosphere. Burning fossil fuels removes carbon-rich material from the geosphere, adds carbon dioxide to the atmosphere, and can affect climate patterns that influence living systems.
Cycles are common GED contexts. In the water cycle, evaporation, condensation, precipitation, runoff, and groundwater movement transfer water through Earth systems. In the carbon cycle, photosynthesis, respiration, decomposition, ocean exchange, and combustion move carbon through living and nonliving parts of the planet. If a question asks what will happen after one process changes, trace the matter or energy through the system.
Natural Hazards and Mitigation
A natural hazard is an event such as an earthquake, hurricane, wildfire, flood, drought, volcanic eruption, or landslide that can harm people or ecosystems. GED questions may ask about frequency, severity, short-term effects, long-term effects, or mitigation. Mitigation means reducing risk, not stopping every hazard. Stronger building codes can reduce earthquake damage, storm shelters can reduce tornado deaths, and wetlands can reduce flooding by absorbing water.
Resources and Sustainability
Environmental systems questions often compare resource choices. Renewable resources can be replenished on a human time scale, such as sunlight, wind, and sustainably managed forests. Nonrenewable resources form so slowly that human use can deplete them, such as coal, oil, natural gas, and many mineral ores.
Sustainability depends on more than whether a resource is renewable. Solar panels produce electricity without burning fuel, but manufacturing and disposal still have material costs. Hydroelectric dams produce renewable electricity, but they can alter rivers and fish habitats. The best GED answer usually weighs evidence from the whole table, not just one positive feature.
Space Models
Space science items often use diagrams. Moon phases depend on the moon's position relative to Earth and the sun. Tides are linked mainly to gravitational interactions among Earth, the moon, and the sun. Eclipses occur when the sun, Earth, and moon line up so that one body blocks light from another.
For stars and galaxies, GED questions usually provide enough context. You may be asked to compare star brightness, sequence a simple star life cycle from a diagram, or interpret evidence about Earth's age from fossils, landforms, or radiometric data. Treat the model as evidence: identify what it shows, then choose the claim it supports.
A coastal town restores wetlands between the ocean and nearby homes. During later storms, floodwater moves more slowly and less sand is washed away. Which statement best explains the role of the wetlands?
A diagram shows the moon directly between Earth and the sun, with the moon's shadow falling on a small part of Earth. Which event does the diagram model?