Overview
This lesson introduces the four subsystems of the Earth—atmosphere, geosphere, biosphere, and hydrosphere—and explains how they interact and depend on each other for maintaining Earth's equilibrium.
The Four Subsystems of Earth
- The atmosphere is the thin layer of gases surrounding Earth, made of 78% nitrogen, 21% oxygen, and 0.9% argon.
- The atmosphere keeps Earth warm, provides oxygen for breathing and CO₂ for photosynthesis, and shields surface from UV radiation.
- Atmospheric circulation and the hydrologic cycle redistribute heat and water across Earth’s surface.
- The geosphere includes Earth's crust, mantle, outer core, and inner core.
- Processes like plate tectonics, erosion, weathering, and volcanic activity shape the geosphere and form landforms.
- Soil in the geosphere provides nutrients and habitat for many life forms.
- The biosphere consists of all living organisms on Earth, estimated between 20-100 million species across five kingdoms.
- The biosphere spans all ecosystems, from soil and forests to oceans and deep sea.
- Photosynthetic organisms in the biosphere form the base of food chains, absorbing CO₂ and releasing O₂.
- The hydrosphere comprises all water on Earth—liquid, solid, and gaseous states.
- About 70% of Earth is covered by water; 3% is fresh, with most of it as ice and the rest in rivers, lakes, and groundwater.
Interactions Between Subsystems
- Earth’s subsystems are interconnected; changes in one affect others.
- Precipitation (hydrosphere and atmosphere) causes erosion and weathering of rocks (geosphere).
- Glaciers (hydrosphere) can erode rocks from the geosphere.
- Both geosphere and hydrosphere provide habitats for the biosphere.
- The biosphere includes both living (biotic) and nonliving (abiotic) factors like water, air, and light.
- Atmospheric gases help maintain temperatures and create conditions for life in the biosphere.
- Human activities, such as burning fossil fuels (biosphere/geosphere), affect atmospheric composition and can impact all systems.
Key Terms & Definitions
- Atmosphere — the layer of gases enveloping Earth, crucial for climate and life.
- Geosphere — the solid part of Earth, including rocks, soil, and core.
- Biosphere — all living organisms and ecosystems on Earth.
- Hydrosphere — all water present on, under, and above Earth’s surface.
- Erosion — process of breaking down and transporting rocks by natural forces.
- Plate Tectonics — movement of Earth's plates shaping the surface.
Action Items / Next Steps
- Complete Activity 1: Describe each subsystem and give three examples of their interactions.
- Complete Activity 2: Use a diagram to identify and illustrate three ways energy and matter flow between the subsystems.