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United StatesEnvironmental Science

Unit 4: Earth Systems and Resources

8 dot points across 8 inquiry questions. Click any dot point for a focused answer with worked past exam questions where available.

What is the air made of, and why does temperature rise and fall as you climb through the atmosphere?

Topic 4.4 Earth's Atmosphere: describe the composition of the atmosphere and the four main layers, and explain how temperature changes with altitude.
A focused answer to APES Topic 4.4, covering atmospheric composition, the four layers (troposphere, stratosphere, mesosphere, thermosphere), the temperature profile, the ozone layer, and the role of the atmosphere in weather and protection, with a worked composition calculation.
9 min answer →

Why is one side of a mountain range lush and the other a desert, and what does El Nino have to do with it?

Topic 4.8 Earth's Geography and Climate: explain how geographic features such as mountains and proximity to water shape regional climate, including rain shadows and El Nino and La Nina.
A focused answer to APES Topic 4.8, covering how mountains, latitude, ocean currents and proximity to water shape regional climate, the rain shadow effect, and the El Nino and La Nina (ENSO) cycle, with a worked rain-shadow question.
10 min answer →

Why are the great deserts found near 30 degrees latitude and the rainforests at the equator?

Topic 4.5 Global Wind Patterns: explain how uneven solar heating and the Coriolis effect drive atmospheric circulation cells and global wind belts.
A focused answer to APES Topic 4.5, covering uneven solar heating, convection and the Hadley, Ferrel and polar cells, the Coriolis effect, the trade winds and westerlies, and why deserts and rainforests sit where they do, with a worked latitude-climate question.
10 min answer →

What drives the slow movement of Earth's plates, and why do earthquakes, volcanoes and mountains cluster where they meet?

Topic 4.1 Plate Tectonics: explain how convection in the mantle drives plate movement and describe the three types of plate boundary and their landforms and hazards.
A focused answer to APES Topic 4.1, covering mantle convection, the three plate boundary types (divergent, convergent, transform), the landforms and hazards each produces, hot spots, and the link to natural resources, with a worked boundary-identification question.
10 min answer →

Why does the mix of sand, silt and clay decide how well a soil holds water and grows crops?

Topic 4.3 Soil Composition and Properties: describe soil texture using the soil triangle, and explain how particle size affects porosity, permeability, water-holding capacity and fertility.
A focused answer to APES Topic 4.3, covering soil texture (sand, silt, clay), the soil texture triangle, porosity and permeability, water-holding capacity, loam, and how texture and pH affect fertility, with a worked soil-triangle question.
9 min answer →

How does solid rock become living soil, and why is that soil so easily lost?

Topic 4.2 Soil Formation and Erosion: explain how soil forms from weathered rock and organic matter, describe the soil horizons, and explain the causes and effects of soil erosion.
A focused answer to APES Topic 4.2, covering weathering, the five soil-forming factors, the soil horizons (O, A, B, C, R), the causes and consequences of soil erosion, and conservation, with a worked soil-loss calculation.
10 min answer →

Why do we have summer and winter, and why is it not simply because Earth is closer to the Sun?

Topic 4.7 Solar Radiation and Earth's Seasons: explain how the tilt of Earth's axis and its orbit produce variations in insolation that cause the seasons.
A focused answer to APES Topic 4.7, covering solar radiation (insolation), the 23.5 degree axial tilt, the solstices and equinoxes, the angle of incidence, why the tilt and not distance causes the seasons, and latitude effects, with a worked insolation question.
9 min answer →

Where does the rain that falls on a hillside actually end up, and what decides how fast it gets there?

Topic 4.6 Watersheds: define a watershed, describe the factors that affect its characteristics, and explain how land use changes runoff and water quality.
A focused answer to APES Topic 4.6, covering the definition of a watershed, divides, the factors that shape watershed behavior (area, slope, vegetation, soil), runoff versus infiltration, and how land use affects flooding and water quality, with a worked runoff comparison.
9 min answer →